Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 4752 insertions, 0 deletions

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
new file mode 100644
index 000000000..36052a362
--- /dev/null
+++ b/fs/ceph/caps.c
@@ -0,0 +1,4752 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/ceph/ceph_debug.h>
+
+#include <linux/fs.h>
+#include <linux/kernel.h>
+#include <linux/sched/signal.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/wait.h>
+#include <linux/writeback.h>
+#include <linux/iversion.h>
+
+#include "super.h"
+#include "mds_client.h"
+#include "cache.h"
+#include <linux/ceph/decode.h>
+#include <linux/ceph/messenger.h>
+
+/*
+ * Capability management
+ *
+ * The Ceph metadata servers control client access to inode metadata
+ * and file data by issuing capabilities, granting clients permission
+ * to read and/or write both inode field and file data to OSDs
+ * (storage nodes).  Each capability consists of a set of bits
+ * indicating which operations are allowed.
+ *
+ * If the client holds a *_SHARED cap, the client has a coherent value
+ * that can be safely read from the cached inode.
+ *
+ * In the case of a *_EXCL (exclusive) or FILE_WR capabilities, the
+ * client is allowed to change inode attributes (e.g., file size,
+ * mtime), note its dirty state in the ceph_cap, and asynchronously
+ * flush that metadata change to the MDS.
+ *
+ * In the event of a conflicting operation (perhaps by another
+ * client), the MDS will revoke the conflicting client capabilities.
+ *
+ * In order for a client to cache an inode, it must hold a capability
+ * with at least one MDS server.  When inodes are released, release
+ * notifications are batched and periodically sent en masse to the MDS
+ * cluster to release server state.
+ */
+
+static u64 __get_oldest_flush_tid(struct ceph_mds_client *mdsc);
+static void __kick_flushing_caps(struct ceph_mds_client *mdsc,
+				 struct ceph_mds_session *session,
+				 struct ceph_inode_info *ci,
+				 u64 oldest_flush_tid);
+
+/*
+ * Generate readable cap strings for debugging output.
+ */
+#define MAX_CAP_STR 20
+static char cap_str[MAX_CAP_STR][40];
+static DEFINE_SPINLOCK(cap_str_lock);
+static int last_cap_str;
+
+static char *gcap_string(char *s, int c)
+{
+	if (c & CEPH_CAP_GSHARED)
+		*s++ = 's';
+	if (c & CEPH_CAP_GEXCL)
+		*s++ = 'x';
+	if (c & CEPH_CAP_GCACHE)
+		*s++ = 'c';
+	if (c & CEPH_CAP_GRD)
+		*s++ = 'r';
+	if (c & CEPH_CAP_GWR)
+		*s++ = 'w';
+	if (c & CEPH_CAP_GBUFFER)
+		*s++ = 'b';
+	if (c & CEPH_CAP_GWREXTEND)
+		*s++ = 'a';
+	if (c & CEPH_CAP_GLAZYIO)
+		*s++ = 'l';
+	return s;
+}
+
+const char *ceph_cap_string(int caps)
+{
+	int i;
+	char *s;
+	int c;
+
+	spin_lock(&cap_str_lock);
+	i = last_cap_str++;
+	if (last_cap_str == MAX_CAP_STR)
+		last_cap_str = 0;
+	spin_unlock(&cap_str_lock);
+
+	s = cap_str[i];
+
+	if (caps & CEPH_CAP_PIN)
+		*s++ = 'p';
+
+	c = (caps >> CEPH_CAP_SAUTH) & 3;
+	if (c) {
+		*s++ = 'A';
+		s = gcap_string(s, c);
+	}
+
+	c = (caps >> CEPH_CAP_SLINK) & 3;
+	if (c) {
+		*s++ = 'L';
+		s = gcap_string(s, c);
+	}
+
+	c = (caps >> CEPH_CAP_SXATTR) & 3;
+	if (c) {
+		*s++ = 'X';
+		s = gcap_string(s, c);
+	}
+
+	c = caps >> CEPH_CAP_SFILE;
+	if (c) {
+		*s++ = 'F';
+		s = gcap_string(s, c);
+	}
+
+	if (s == cap_str[i])
+		*s++ = '-';
+	*s = 0;
+	return cap_str[i];
+}
+
+void ceph_caps_init(struct ceph_mds_client *mdsc)
+{
+	INIT_LIST_HEAD(&mdsc->caps_list);
+	spin_lock_init(&mdsc->caps_list_lock);
+}
+
+void ceph_caps_finalize(struct ceph_mds_client *mdsc)
+{
+	struct ceph_cap *cap;
+
+	spin_lock(&mdsc->caps_list_lock);
+	while (!list_empty(&mdsc->caps_list)) {
+		cap = list_first_entry(&mdsc->caps_list,
+				       struct ceph_cap, caps_item);
+		list_del(&cap->caps_item);
+		kmem_cache_free(ceph_cap_cachep, cap);
+	}
+	mdsc->caps_total_count = 0;
+	mdsc->caps_avail_count = 0;
+	mdsc->caps_use_count = 0;
+	mdsc->caps_reserve_count = 0;
+	mdsc->caps_min_count = 0;
+	spin_unlock(&mdsc->caps_list_lock);
+}
+
+void ceph_adjust_caps_max_min(struct ceph_mds_client *mdsc,
+			      struct ceph_mount_options *fsopt)
+{
+	spin_lock(&mdsc->caps_list_lock);
+	mdsc->caps_min_count = fsopt->max_readdir;
+	if (mdsc->caps_min_count < 1024)
+		mdsc->caps_min_count = 1024;
+	mdsc->caps_use_max = fsopt->caps_max;
+	if (mdsc->caps_use_max > 0 &&
+	    mdsc->caps_use_max < mdsc->caps_min_count)
+		mdsc->caps_use_max = mdsc->caps_min_count;
+	spin_unlock(&mdsc->caps_list_lock);
+}
+
+static void __ceph_unreserve_caps(struct ceph_mds_client *mdsc, int nr_caps)
+{
+	struct ceph_cap *cap;
+	int i;
+
+	if (nr_caps) {
+		BUG_ON(mdsc->caps_reserve_count < nr_caps);
+		mdsc->caps_reserve_count -= nr_caps;
+		if (mdsc->caps_avail_count >=
+		    mdsc->caps_reserve_count + mdsc->caps_min_count) {
+			mdsc->caps_total_count -= nr_caps;
+			for (i = 0; i < nr_caps; i++) {
+				cap = list_first_entry(&mdsc->caps_list,
+					struct ceph_cap, caps_item);
+				list_del(&cap->caps_item);
+				kmem_cache_free(ceph_cap_cachep, cap);
+			}
+		} else {
+			mdsc->caps_avail_count += nr_caps;
+		}
+
+		dout("%s: caps %d = %d used + %d resv + %d avail\n",
+		     __func__,
+		     mdsc->caps_total_count, mdsc->caps_use_count,
+		     mdsc->caps_reserve_count, mdsc->caps_avail_count);
+		BUG_ON(mdsc->caps_total_count != mdsc->caps_use_count +
+						 mdsc->caps_reserve_count +
+						 mdsc->caps_avail_count);
+	}
+}
+
+/*
+ * Called under mdsc->mutex.
+ */
+int ceph_reserve_caps(struct ceph_mds_client *mdsc,
+		      struct ceph_cap_reservation *ctx, int need)
+{
+	int i, j;
+	struct ceph_cap *cap;
+	int have;
+	int alloc = 0;
+	int max_caps;
+	int err = 0;
+	bool trimmed = false;
+	struct ceph_mds_session *s;
+	LIST_HEAD(newcaps);
+
+	dout("reserve caps ctx=%p need=%d\n", ctx, need);
+
+	/* first reserve any caps that are already allocated */
+	spin_lock(&mdsc->caps_list_lock);
+	if (mdsc->caps_avail_count >= need)
+		have = need;
+	else
+		have = mdsc->caps_avail_count;
+	mdsc->caps_avail_count -= have;
+	mdsc->caps_reserve_count += have;
+	BUG_ON(mdsc->caps_total_count != mdsc->caps_use_count +
+					 mdsc->caps_reserve_count +
+					 mdsc->caps_avail_count);
+	spin_unlock(&mdsc->caps_list_lock);
+
+	for (i = have; i < need; ) {
+		cap = kmem_cache_alloc(ceph_cap_cachep, GFP_NOFS);
+		if (cap) {
+			list_add(&cap->caps_item, &newcaps);
+			alloc++;
+			i++;
+			continue;
+		}
+
+		if (!trimmed) {
+			for (j = 0; j < mdsc->max_sessions; j++) {
+				s = __ceph_lookup_mds_session(mdsc, j);
+				if (!s)
+					continue;
+				mutex_unlock(&mdsc->mutex);
+
+				mutex_lock(&s->s_mutex);
+				max_caps = s->s_nr_caps - (need - i);
+				ceph_trim_caps(mdsc, s, max_caps);
+				mutex_unlock(&s->s_mutex);
+
+				ceph_put_mds_session(s);
+				mutex_lock(&mdsc->mutex);
+			}
+			trimmed = true;
+
+			spin_lock(&mdsc->caps_list_lock);
+			if (mdsc->caps_avail_count) {
+				int more_have;
+				if (mdsc->caps_avail_count >= need - i)
+					more_have = need - i;
+				else
+					more_have = mdsc->caps_avail_count;
+
+				i += more_have;
+				have += more_have;
+				mdsc->caps_avail_count -= more_have;
+				mdsc->caps_reserve_count += more_have;
+
+			}
+			spin_unlock(&mdsc->caps_list_lock);
+
+			continue;
+		}
+
+		pr_warn("reserve caps ctx=%p ENOMEM need=%d got=%d\n",
+			ctx, need, have + alloc);
+		err = -ENOMEM;
+		break;
+	}
+
+	if (!err) {
+		BUG_ON(have + alloc != need);
+		ctx->count = need;
+		ctx->used = 0;
+	}
+
+	spin_lock(&mdsc->caps_list_lock);
+	mdsc->caps_total_count += alloc;
+	mdsc->caps_reserve_count += alloc;
+	list_splice(&newcaps, &mdsc->caps_list);
+
+	BUG_ON(mdsc->caps_total_count != mdsc->caps_use_count +
+					 mdsc->caps_reserve_count +
+					 mdsc->caps_avail_count);
+
+	if (err)
+		__ceph_unreserve_caps(mdsc, have + alloc);
+
+	spin_unlock(&mdsc->caps_list_lock);
+
+	dout("reserve caps ctx=%p %d = %d used + %d resv + %d avail\n",
+	     ctx, mdsc->caps_total_count, mdsc->caps_use_count,
+	     mdsc->caps_reserve_count, mdsc->caps_avail_count);
+	return err;
+}
+
+void ceph_unreserve_caps(struct ceph_mds_client *mdsc,
+			 struct ceph_cap_reservation *ctx)
+{
+	bool reclaim = false;
+	if (!ctx->count)
+		return;
+
+	dout("unreserve caps ctx=%p count=%d\n", ctx, ctx->count);
+	spin_lock(&mdsc->caps_list_lock);
+	__ceph_unreserve_caps(mdsc, ctx->count);
+	ctx->count = 0;
+
+	if (mdsc->caps_use_max > 0 &&
+	    mdsc->caps_use_count > mdsc->caps_use_max)
+		reclaim = true;
+	spin_unlock(&mdsc->caps_list_lock);
+
+	if (reclaim)
+		ceph_reclaim_caps_nr(mdsc, ctx->used);
+}
+
+struct ceph_cap *ceph_get_cap(struct ceph_mds_client *mdsc,
+			      struct ceph_cap_reservation *ctx)
+{
+	struct ceph_cap *cap = NULL;
+
+	/* temporary, until we do something about cap import/export */
+	if (!ctx) {
+		cap = kmem_cache_alloc(ceph_cap_cachep, GFP_NOFS);
+		if (cap) {
+			spin_lock(&mdsc->caps_list_lock);
+			mdsc->caps_use_count++;
+			mdsc->caps_total_count++;
+			spin_unlock(&mdsc->caps_list_lock);
+		} else {
+			spin_lock(&mdsc->caps_list_lock);
+			if (mdsc->caps_avail_count) {
+				BUG_ON(list_empty(&mdsc->caps_list));
+
+				mdsc->caps_avail_count--;
+				mdsc->caps_use_count++;
+				cap = list_first_entry(&mdsc->caps_list,
+						struct ceph_cap, caps_item);
+				list_del(&cap->caps_item);
+
+				BUG_ON(mdsc->caps_total_count != mdsc->caps_use_count +
+				       mdsc->caps_reserve_count + mdsc->caps_avail_count);
+			}
+			spin_unlock(&mdsc->caps_list_lock);
+		}
+
+		return cap;
+	}
+
+	spin_lock(&mdsc->caps_list_lock);
+	dout("get_cap ctx=%p (%d) %d = %d used + %d resv + %d avail\n",
+	     ctx, ctx->count, mdsc->caps_total_count, mdsc->caps_use_count,
+	     mdsc->caps_reserve_count, mdsc->caps_avail_count);
+	BUG_ON(!ctx->count);
+	BUG_ON(ctx->count > mdsc->caps_reserve_count);
+	BUG_ON(list_empty(&mdsc->caps_list));
+
+	ctx->count--;
+	ctx->used++;
+	mdsc->caps_reserve_count--;
+	mdsc->caps_use_count++;
+
+	cap = list_first_entry(&mdsc->caps_list, struct ceph_cap, caps_item);
+	list_del(&cap->caps_item);
+
+	BUG_ON(mdsc->caps_total_count != mdsc->caps_use_count +
+	       mdsc->caps_reserve_count + mdsc->caps_avail_count);
+	spin_unlock(&mdsc->caps_list_lock);
+	return cap;
+}
+
+void ceph_put_cap(struct ceph_mds_client *mdsc, struct ceph_cap *cap)
+{
+	spin_lock(&mdsc->caps_list_lock);
+	dout("put_cap %p %d = %d used + %d resv + %d avail\n",
+	     cap, mdsc->caps_total_count, mdsc->caps_use_count,
+	     mdsc->caps_reserve_count, mdsc->caps_avail_count);
+	mdsc->caps_use_count--;
+	/*
+	 * Keep some preallocated caps around (ceph_min_count), to
+	 * avoid lots of free/alloc churn.
+	 */
+	if (mdsc->caps_avail_count >= mdsc->caps_reserve_count +
+				      mdsc->caps_min_count) {
+		mdsc->caps_total_count--;
+		kmem_cache_free(ceph_cap_cachep, cap);
+	} else {
+		mdsc->caps_avail_count++;
+		list_add(&cap->caps_item, &mdsc->caps_list);
+	}
+
+	BUG_ON(mdsc->caps_total_count != mdsc->caps_use_count +
+	       mdsc->caps_reserve_count + mdsc->caps_avail_count);
+	spin_unlock(&mdsc->caps_list_lock);
+}
+
+void ceph_reservation_status(struct ceph_fs_client *fsc,
+			     int *total, int *avail, int *used, int *reserved,
+			     int *min)
+{
+	struct ceph_mds_client *mdsc = fsc->mdsc;
+
+	spin_lock(&mdsc->caps_list_lock);
+
+	if (total)
+		*total = mdsc->caps_total_count;
+	if (avail)
+		*avail = mdsc->caps_avail_count;
+	if (used)
+		*used = mdsc->caps_use_count;
+	if (reserved)
+		*reserved = mdsc->caps_reserve_count;
+	if (min)
+		*min = mdsc->caps_min_count;
+
+	spin_unlock(&mdsc->caps_list_lock);
+}
+
+/*
+ * Find ceph_cap for given mds, if any.
+ *
+ * Called with i_ceph_lock held.
+ */
+struct ceph_cap *__get_cap_for_mds(struct ceph_inode_info *ci, int mds)
+{
+	struct ceph_cap *cap;
+	struct rb_node *n = ci->i_caps.rb_node;
+
+	while (n) {
+		cap = rb_entry(n, struct ceph_cap, ci_node);
+		if (mds < cap->mds)
+			n = n->rb_left;
+		else if (mds > cap->mds)
+			n = n->rb_right;
+		else
+			return cap;
+	}
+	return NULL;
+}
+
+struct ceph_cap *ceph_get_cap_for_mds(struct ceph_inode_info *ci, int mds)
+{
+	struct ceph_cap *cap;
+
+	spin_lock(&ci->i_ceph_lock);
+	cap = __get_cap_for_mds(ci, mds);
+	spin_unlock(&ci->i_ceph_lock);
+	return cap;
+}
+
+/*
+ * Called under i_ceph_lock.
+ */
+static void __insert_cap_node(struct ceph_inode_info *ci,
+			      struct ceph_cap *new)
+{
+	struct rb_node **p = &ci->i_caps.rb_node;
+	struct rb_node *parent = NULL;
+	struct ceph_cap *cap = NULL;
+
+	while (*p) {
+		parent = *p;
+		cap = rb_entry(parent, struct ceph_cap, ci_node);
+		if (new->mds < cap->mds)
+			p = &(*p)->rb_left;
+		else if (new->mds > cap->mds)
+			p = &(*p)->rb_right;
+		else
+			BUG();
+	}
+
+	rb_link_node(&new->ci_node, parent, p);
+	rb_insert_color(&new->ci_node, &ci->i_caps);
+}
+
+/*
+ * (re)set cap hold timeouts, which control the delayed release
+ * of unused caps back to the MDS.  Should be called on cap use.
+ */
+static void __cap_set_timeouts(struct ceph_mds_client *mdsc,
+			       struct ceph_inode_info *ci)
+{
+	struct ceph_mount_options *opt = mdsc->fsc->mount_options;
+	ci->i_hold_caps_max = round_jiffies(jiffies +
+					    opt->caps_wanted_delay_max * HZ);
+	dout("__cap_set_timeouts %p %lu\n", &ci->netfs.inode,
+	     ci->i_hold_caps_max - jiffies);
+}
+
+/*
+ * (Re)queue cap at the end of the delayed cap release list.
+ *
+ * If I_FLUSH is set, leave the inode at the front of the list.
+ *
+ * Caller holds i_ceph_lock
+ *    -> we take mdsc->cap_delay_lock
+ */
+static void __cap_delay_requeue(struct ceph_mds_client *mdsc,
+				struct ceph_inode_info *ci)
+{
+	dout("__cap_delay_requeue %p flags 0x%lx at %lu\n", &ci->netfs.inode,
+	     ci->i_ceph_flags, ci->i_hold_caps_max);
+	if (!mdsc->stopping) {
+		spin_lock(&mdsc->cap_delay_lock);
+		if (!list_empty(&ci->i_cap_delay_list)) {
+			if (ci->i_ceph_flags & CEPH_I_FLUSH)
+				goto no_change;
+			list_del_init(&ci->i_cap_delay_list);
+		}
+		__cap_set_timeouts(mdsc, ci);
+		list_add_tail(&ci->i_cap_delay_list, &mdsc->cap_delay_list);
+no_change:
+		spin_unlock(&mdsc->cap_delay_lock);
+	}
+}
+
+/*
+ * Queue an inode for immediate writeback.  Mark inode with I_FLUSH,
+ * indicating we should send a cap message to flush dirty metadata
+ * asap, and move to the front of the delayed cap list.
+ */
+static void __cap_delay_requeue_front(struct ceph_mds_client *mdsc,
+				      struct ceph_inode_info *ci)
+{
+	dout("__cap_delay_requeue_front %p\n", &ci->netfs.inode);
+	spin_lock(&mdsc->cap_delay_lock);
+	ci->i_ceph_flags |= CEPH_I_FLUSH;
+	if (!list_empty(&ci->i_cap_delay_list))
+		list_del_init(&ci->i_cap_delay_list);
+	list_add(&ci->i_cap_delay_list, &mdsc->cap_delay_list);
+	spin_unlock(&mdsc->cap_delay_lock);
+}
+
+/*
+ * Cancel delayed work on cap.
+ *
+ * Caller must hold i_ceph_lock.
+ */
+static void __cap_delay_cancel(struct ceph_mds_client *mdsc,
+			       struct ceph_inode_info *ci)
+{
+	dout("__cap_delay_cancel %p\n", &ci->netfs.inode);
+	if (list_empty(&ci->i_cap_delay_list))
+		return;
+	spin_lock(&mdsc->cap_delay_lock);
+	list_del_init(&ci->i_cap_delay_list);
+	spin_unlock(&mdsc->cap_delay_lock);
+}
+
+/* Common issue checks for add_cap, handle_cap_grant. */
+static void __check_cap_issue(struct ceph_inode_info *ci, struct ceph_cap *cap,
+			      unsigned issued)
+{
+	unsigned had = __ceph_caps_issued(ci, NULL);
+
+	lockdep_assert_held(&ci->i_ceph_lock);
+
+	/*
+	 * Each time we receive FILE_CACHE anew, we increment
+	 * i_rdcache_gen.
+	 */
+	if (S_ISREG(ci->netfs.inode.i_mode) &&
+	    (issued & (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO)) &&
+	    (had & (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO)) == 0) {
+		ci->i_rdcache_gen++;
+	}
+
+	/*
+	 * If FILE_SHARED is newly issued, mark dir not complete. We don't
+	 * know what happened to this directory while we didn't have the cap.
+	 * If FILE_SHARED is being revoked, also mark dir not complete. It
+	 * stops on-going cached readdir.
+	 */
+	if ((issued & CEPH_CAP_FILE_SHARED) != (had & CEPH_CAP_FILE_SHARED)) {
+		if (issued & CEPH_CAP_FILE_SHARED)
+			atomic_inc(&ci->i_shared_gen);
+		if (S_ISDIR(ci->netfs.inode.i_mode)) {
+			dout(" marking %p NOT complete\n", &ci->netfs.inode);
+			__ceph_dir_clear_complete(ci);
+		}
+	}
+
+	/* Wipe saved layout if we're losing DIR_CREATE caps */
+	if (S_ISDIR(ci->netfs.inode.i_mode) && (had & CEPH_CAP_DIR_CREATE) &&
+		!(issued & CEPH_CAP_DIR_CREATE)) {
+	     ceph_put_string(rcu_dereference_raw(ci->i_cached_layout.pool_ns));
+	     memset(&ci->i_cached_layout, 0, sizeof(ci->i_cached_layout));
+	}
+}
+
+/**
+ * change_auth_cap_ses - move inode to appropriate lists when auth caps change
+ * @ci: inode to be moved
+ * @session: new auth caps session
+ */
+void change_auth_cap_ses(struct ceph_inode_info *ci,
+			 struct ceph_mds_session *session)
+{
+	lockdep_assert_held(&ci->i_ceph_lock);
+
+	if (list_empty(&ci->i_dirty_item) && list_empty(&ci->i_flushing_item))
+		return;
+
+	spin_lock(&session->s_mdsc->cap_dirty_lock);
+	if (!list_empty(&ci->i_dirty_item))
+		list_move(&ci->i_dirty_item, &session->s_cap_dirty);
+	if (!list_empty(&ci->i_flushing_item))
+		list_move_tail(&ci->i_flushing_item, &session->s_cap_flushing);
+	spin_unlock(&session->s_mdsc->cap_dirty_lock);
+}
+
+/*
+ * Add a capability under the given MDS session.
+ *
+ * Caller should hold session snap_rwsem (read) and ci->i_ceph_lock
+ *
+ * @fmode is the open file mode, if we are opening a file, otherwise
+ * it is < 0.  (This is so we can atomically add the cap and add an
+ * open file reference to it.)
+ */
+void ceph_add_cap(struct inode *inode,
+		  struct ceph_mds_session *session, u64 cap_id,
+		  unsigned issued, unsigned wanted,
+		  unsigned seq, unsigned mseq, u64 realmino, int flags,
+		  struct ceph_cap **new_cap)
+{
+	struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_cap *cap;
+	int mds = session->s_mds;
+	int actual_wanted;
+	u32 gen;
+
+	lockdep_assert_held(&ci->i_ceph_lock);
+
+	dout("add_cap %p mds%d cap %llx %s seq %d\n", inode,
+	     session->s_mds, cap_id, ceph_cap_string(issued), seq);
+
+	gen = atomic_read(&session->s_cap_gen);
+
+	cap = __get_cap_for_mds(ci, mds);
+	if (!cap) {
+		cap = *new_cap;
+		*new_cap = NULL;
+
+		cap->issued = 0;
+		cap->implemented = 0;
+		cap->mds = mds;
+		cap->mds_wanted = 0;
+		cap->mseq = 0;
+
+		cap->ci = ci;
+		__insert_cap_node(ci, cap);
+
+		/* add to session cap list */
+		cap->session = session;
+		spin_lock(&session->s_cap_lock);
+		list_add_tail(&cap->session_caps, &session->s_caps);
+		session->s_nr_caps++;
+		atomic64_inc(&mdsc->metric.total_caps);
+		spin_unlock(&session->s_cap_lock);
+	} else {
+		spin_lock(&session->s_cap_lock);
+		list_move_tail(&cap->session_caps, &session->s_caps);
+		spin_unlock(&session->s_cap_lock);
+
+		if (cap->cap_gen < gen)
+			cap->issued = cap->implemented = CEPH_CAP_PIN;
+
+		/*
+		 * auth mds of the inode changed. we received the cap export
+		 * message, but still haven't received the cap import message.
+		 * handle_cap_export() updated the new auth MDS' cap.
+		 *
+		 * "ceph_seq_cmp(seq, cap->seq) <= 0" means we are processing
+		 * a message that was send before the cap import message. So
+		 * don't remove caps.
+		 */
+		if (ceph_seq_cmp(seq, cap->seq) <= 0) {
+			WARN_ON(cap != ci->i_auth_cap);
+			WARN_ON(cap->cap_id != cap_id);
+			seq = cap->seq;
+			mseq = cap->mseq;
+			issued |= cap->issued;
+			flags |= CEPH_CAP_FLAG_AUTH;
+		}
+	}
+
+	if (!ci->i_snap_realm ||
+	    ((flags & CEPH_CAP_FLAG_AUTH) &&
+	     realmino != (u64)-1 && ci->i_snap_realm->ino != realmino)) {
+		/*
+		 * add this inode to the appropriate snap realm
+		 */
+		struct ceph_snap_realm *realm = ceph_lookup_snap_realm(mdsc,
+							       realmino);
+		if (realm)
+			ceph_change_snap_realm(inode, realm);
+		else
+			WARN(1, "%s: couldn't find snap realm 0x%llx (ino 0x%llx oldrealm 0x%llx)\n",
+			     __func__, realmino, ci->i_vino.ino,
+			     ci->i_snap_realm ? ci->i_snap_realm->ino : 0);
+	}
+
+	__check_cap_issue(ci, cap, issued);
+
+	/*
+	 * If we are issued caps we don't want, or the mds' wanted
+	 * value appears to be off, queue a check so we'll release
+	 * later and/or update the mds wanted value.
+	 */
+	actual_wanted = __ceph_caps_wanted(ci);
+	if ((wanted & ~actual_wanted) ||
+	    (issued & ~actual_wanted & CEPH_CAP_ANY_WR)) {
+		dout(" issued %s, mds wanted %s, actual %s, queueing\n",
+		     ceph_cap_string(issued), ceph_cap_string(wanted),
+		     ceph_cap_string(actual_wanted));
+		__cap_delay_requeue(mdsc, ci);
+	}
+
+	if (flags & CEPH_CAP_FLAG_AUTH) {
+		if (!ci->i_auth_cap ||
+		    ceph_seq_cmp(ci->i_auth_cap->mseq, mseq) < 0) {
+			if (ci->i_auth_cap &&
+			    ci->i_auth_cap->session != cap->session)
+				change_auth_cap_ses(ci, cap->session);
+			ci->i_auth_cap = cap;
+			cap->mds_wanted = wanted;
+		}
+	} else {
+		WARN_ON(ci->i_auth_cap == cap);
+	}
+
+	dout("add_cap inode %p (%llx.%llx) cap %p %s now %s seq %d mds%d\n",
+	     inode, ceph_vinop(inode), cap, ceph_cap_string(issued),
+	     ceph_cap_string(issued|cap->issued), seq, mds);
+	cap->cap_id = cap_id;
+	cap->issued = issued;
+	cap->implemented |= issued;
+	if (ceph_seq_cmp(mseq, cap->mseq) > 0)
+		cap->mds_wanted = wanted;
+	else
+		cap->mds_wanted |= wanted;
+	cap->seq = seq;
+	cap->issue_seq = seq;
+	cap->mseq = mseq;
+	cap->cap_gen = gen;
+	wake_up_all(&ci->i_cap_wq);
+}
+
+/*
+ * Return true if cap has not timed out and belongs to the current
+ * generation of the MDS session (i.e. has not gone 'stale' due to
+ * us losing touch with the mds).
+ */
+static int __cap_is_valid(struct ceph_cap *cap)
+{
+	unsigned long ttl;
+	u32 gen;
+
+	gen = atomic_read(&cap->session->s_cap_gen);
+	ttl = cap->session->s_cap_ttl;
+
+	if (cap->cap_gen < gen || time_after_eq(jiffies, ttl)) {
+		dout("__cap_is_valid %p cap %p issued %s "
+		     "but STALE (gen %u vs %u)\n", &cap->ci->netfs.inode,
+		     cap, ceph_cap_string(cap->issued), cap->cap_gen, gen);
+		return 0;
+	}
+
+	return 1;
+}
+
+/*
+ * Return set of valid cap bits issued to us.  Note that caps time
+ * out, and may be invalidated in bulk if the client session times out
+ * and session->s_cap_gen is bumped.
+ */
+int __ceph_caps_issued(struct ceph_inode_info *ci, int *implemented)
+{
+	int have = ci->i_snap_caps;
+	struct ceph_cap *cap;
+	struct rb_node *p;
+
+	if (implemented)
+		*implemented = 0;
+	for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
+		cap = rb_entry(p, struct ceph_cap, ci_node);
+		if (!__cap_is_valid(cap))
+			continue;
+		dout("__ceph_caps_issued %p cap %p issued %s\n",
+		     &ci->netfs.inode, cap, ceph_cap_string(cap->issued));
+		have |= cap->issued;
+		if (implemented)
+			*implemented |= cap->implemented;
+	}
+	/*
+	 * exclude caps issued by non-auth MDS, but are been revoking
+	 * by the auth MDS. The non-auth MDS should be revoking/exporting
+	 * these caps, but the message is delayed.
+	 */
+	if (ci->i_auth_cap) {
+		cap = ci->i_auth_cap;
+		have &= ~cap->implemented | cap->issued;
+	}
+	return have;
+}
+
+/*
+ * Get cap bits issued by caps other than @ocap
+ */
+int __ceph_caps_issued_other(struct ceph_inode_info *ci, struct ceph_cap *ocap)
+{
+	int have = ci->i_snap_caps;
+	struct ceph_cap *cap;
+	struct rb_node *p;
+
+	for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
+		cap = rb_entry(p, struct ceph_cap, ci_node);
+		if (cap == ocap)
+			continue;
+		if (!__cap_is_valid(cap))
+			continue;
+		have |= cap->issued;
+	}
+	return have;
+}
+
+/*
+ * Move a cap to the end of the LRU (oldest caps at list head, newest
+ * at list tail).
+ */
+static void __touch_cap(struct ceph_cap *cap)
+{
+	struct ceph_mds_session *s = cap->session;
+
+	spin_lock(&s->s_cap_lock);
+	if (!s->s_cap_iterator) {
+		dout("__touch_cap %p cap %p mds%d\n", &cap->ci->netfs.inode, cap,
+		     s->s_mds);
+		list_move_tail(&cap->session_caps, &s->s_caps);
+	} else {
+		dout("__touch_cap %p cap %p mds%d NOP, iterating over caps\n",
+		     &cap->ci->netfs.inode, cap, s->s_mds);
+	}
+	spin_unlock(&s->s_cap_lock);
+}
+
+/*
+ * Check if we hold the given mask.  If so, move the cap(s) to the
+ * front of their respective LRUs.  (This is the preferred way for
+ * callers to check for caps they want.)
+ */
+int __ceph_caps_issued_mask(struct ceph_inode_info *ci, int mask, int touch)
+{
+	struct ceph_cap *cap;
+	struct rb_node *p;
+	int have = ci->i_snap_caps;
+
+	if ((have & mask) == mask) {
+		dout("__ceph_caps_issued_mask ino 0x%llx snap issued %s"
+		     " (mask %s)\n", ceph_ino(&ci->netfs.inode),
+		     ceph_cap_string(have),
+		     ceph_cap_string(mask));
+		return 1;
+	}
+
+	for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
+		cap = rb_entry(p, struct ceph_cap, ci_node);
+		if (!__cap_is_valid(cap))
+			continue;
+		if ((cap->issued & mask) == mask) {
+			dout("__ceph_caps_issued_mask ino 0x%llx cap %p issued %s"
+			     " (mask %s)\n", ceph_ino(&ci->netfs.inode), cap,
+			     ceph_cap_string(cap->issued),
+			     ceph_cap_string(mask));
+			if (touch)
+				__touch_cap(cap);
+			return 1;
+		}
+
+		/* does a combination of caps satisfy mask? */
+		have |= cap->issued;
+		if ((have & mask) == mask) {
+			dout("__ceph_caps_issued_mask ino 0x%llx combo issued %s"
+			     " (mask %s)\n", ceph_ino(&ci->netfs.inode),
+			     ceph_cap_string(cap->issued),
+			     ceph_cap_string(mask));
+			if (touch) {
+				struct rb_node *q;
+
+				/* touch this + preceding caps */
+				__touch_cap(cap);
+				for (q = rb_first(&ci->i_caps); q != p;
+				     q = rb_next(q)) {
+					cap = rb_entry(q, struct ceph_cap,
+						       ci_node);
+					if (!__cap_is_valid(cap))
+						continue;
+					if (cap->issued & mask)
+						__touch_cap(cap);
+				}
+			}
+			return 1;
+		}
+	}
+
+	return 0;
+}
+
+int __ceph_caps_issued_mask_metric(struct ceph_inode_info *ci, int mask,
+				   int touch)
+{
+	struct ceph_fs_client *fsc = ceph_sb_to_client(ci->netfs.inode.i_sb);
+	int r;
+
+	r = __ceph_caps_issued_mask(ci, mask, touch);
+	if (r)
+		ceph_update_cap_hit(&fsc->mdsc->metric);
+	else
+		ceph_update_cap_mis(&fsc->mdsc->metric);
+	return r;
+}
+
+/*
+ * Return true if mask caps are currently being revoked by an MDS.
+ */
+int __ceph_caps_revoking_other(struct ceph_inode_info *ci,
+			       struct ceph_cap *ocap, int mask)
+{
+	struct ceph_cap *cap;
+	struct rb_node *p;
+
+	for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
+		cap = rb_entry(p, struct ceph_cap, ci_node);
+		if (cap != ocap &&
+		    (cap->implemented & ~cap->issued & mask))
+			return 1;
+	}
+	return 0;
+}
+
+int ceph_caps_revoking(struct ceph_inode_info *ci, int mask)
+{
+	struct inode *inode = &ci->netfs.inode;
+	int ret;
+
+	spin_lock(&ci->i_ceph_lock);
+	ret = __ceph_caps_revoking_other(ci, NULL, mask);
+	spin_unlock(&ci->i_ceph_lock);
+	dout("ceph_caps_revoking %p %s = %d\n", inode,
+	     ceph_cap_string(mask), ret);
+	return ret;
+}
+
+int __ceph_caps_used(struct ceph_inode_info *ci)
+{
+	int used = 0;
+	if (ci->i_pin_ref)
+		used |= CEPH_CAP_PIN;
+	if (ci->i_rd_ref)
+		used |= CEPH_CAP_FILE_RD;
+	if (ci->i_rdcache_ref ||
+	    (S_ISREG(ci->netfs.inode.i_mode) &&
+	     ci->netfs.inode.i_data.nrpages))
+		used |= CEPH_CAP_FILE_CACHE;
+	if (ci->i_wr_ref)
+		used |= CEPH_CAP_FILE_WR;
+	if (ci->i_wb_ref || ci->i_wrbuffer_ref)
+		used |= CEPH_CAP_FILE_BUFFER;
+	if (ci->i_fx_ref)
+		used |= CEPH_CAP_FILE_EXCL;
+	return used;
+}
+
+#define FMODE_WAIT_BIAS 1000
+
+/*
+ * wanted, by virtue of open file modes
+ */
+int __ceph_caps_file_wanted(struct ceph_inode_info *ci)
+{
+	const int PIN_SHIFT = ffs(CEPH_FILE_MODE_PIN);
+	const int RD_SHIFT = ffs(CEPH_FILE_MODE_RD);
+	const int WR_SHIFT = ffs(CEPH_FILE_MODE_WR);
+	const int LAZY_SHIFT = ffs(CEPH_FILE_MODE_LAZY);
+	struct ceph_mount_options *opt =
+		ceph_inode_to_client(&ci->netfs.inode)->mount_options;
+	unsigned long used_cutoff = jiffies - opt->caps_wanted_delay_max * HZ;
+	unsigned long idle_cutoff = jiffies - opt->caps_wanted_delay_min * HZ;
+
+	if (S_ISDIR(ci->netfs.inode.i_mode)) {
+		int want = 0;
+
+		/* use used_cutoff here, to keep dir's wanted caps longer */
+		if (ci->i_nr_by_mode[RD_SHIFT] > 0 ||
+		    time_after(ci->i_last_rd, used_cutoff))
+			want |= CEPH_CAP_ANY_SHARED;
+
+		if (ci->i_nr_by_mode[WR_SHIFT] > 0 ||
+		    time_after(ci->i_last_wr, used_cutoff)) {
+			want |= CEPH_CAP_ANY_SHARED | CEPH_CAP_FILE_EXCL;
+			if (opt->flags & CEPH_MOUNT_OPT_ASYNC_DIROPS)
+				want |= CEPH_CAP_ANY_DIR_OPS;
+		}
+
+		if (want || ci->i_nr_by_mode[PIN_SHIFT] > 0)
+			want |= CEPH_CAP_PIN;
+
+		return want;
+	} else {
+		int bits = 0;
+
+		if (ci->i_nr_by_mode[RD_SHIFT] > 0) {
+			if (ci->i_nr_by_mode[RD_SHIFT] >= FMODE_WAIT_BIAS ||
+			    time_after(ci->i_last_rd, used_cutoff))
+				bits |= 1 << RD_SHIFT;
+		} else if (time_after(ci->i_last_rd, idle_cutoff)) {
+			bits |= 1 << RD_SHIFT;
+		}
+
+		if (ci->i_nr_by_mode[WR_SHIFT] > 0) {
+			if (ci->i_nr_by_mode[WR_SHIFT] >= FMODE_WAIT_BIAS ||
+			    time_after(ci->i_last_wr, used_cutoff))
+				bits |= 1 << WR_SHIFT;
+		} else if (time_after(ci->i_last_wr, idle_cutoff)) {
+			bits |= 1 << WR_SHIFT;
+		}
+
+		/* check lazyio only when read/write is wanted */
+		if ((bits & (CEPH_FILE_MODE_RDWR << 1)) &&
+		    ci->i_nr_by_mode[LAZY_SHIFT] > 0)
+			bits |= 1 << LAZY_SHIFT;
+
+		return bits ? ceph_caps_for_mode(bits >> 1) : 0;
+	}
+}
+
+/*
+ * wanted, by virtue of open file modes AND cap refs (buffered/cached data)
+ */
+int __ceph_caps_wanted(struct ceph_inode_info *ci)
+{
+	int w = __ceph_caps_file_wanted(ci) | __ceph_caps_used(ci);
+	if (S_ISDIR(ci->netfs.inode.i_mode)) {
+		/* we want EXCL if holding caps of dir ops */
+		if (w & CEPH_CAP_ANY_DIR_OPS)
+			w |= CEPH_CAP_FILE_EXCL;
+	} else {
+		/* we want EXCL if dirty data */
+		if (w & CEPH_CAP_FILE_BUFFER)
+			w |= CEPH_CAP_FILE_EXCL;
+	}
+	return w;
+}
+
+/*
+ * Return caps we have registered with the MDS(s) as 'wanted'.
+ */
+int __ceph_caps_mds_wanted(struct ceph_inode_info *ci, bool check)
+{
+	struct ceph_cap *cap;
+	struct rb_node *p;
+	int mds_wanted = 0;
+
+	for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
+		cap = rb_entry(p, struct ceph_cap, ci_node);
+		if (check && !__cap_is_valid(cap))
+			continue;
+		if (cap == ci->i_auth_cap)
+			mds_wanted |= cap->mds_wanted;
+		else
+			mds_wanted |= (cap->mds_wanted & ~CEPH_CAP_ANY_FILE_WR);
+	}
+	return mds_wanted;
+}
+
+int ceph_is_any_caps(struct inode *inode)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	int ret;
+
+	spin_lock(&ci->i_ceph_lock);
+	ret = __ceph_is_any_real_caps(ci);
+	spin_unlock(&ci->i_ceph_lock);
+
+	return ret;
+}
+
+/*
+ * Remove a cap.  Take steps to deal with a racing iterate_session_caps.
+ *
+ * caller should hold i_ceph_lock.
+ * caller will not hold session s_mutex if called from destroy_inode.
+ */
+void __ceph_remove_cap(struct ceph_cap *cap, bool queue_release)
+{
+	struct ceph_mds_session *session = cap->session;
+	struct ceph_inode_info *ci = cap->ci;
+	struct ceph_mds_client *mdsc;
+	int removed = 0;
+
+	/* 'ci' being NULL means the remove have already occurred */
+	if (!ci) {
+		dout("%s: cap inode is NULL\n", __func__);
+		return;
+	}
+
+	lockdep_assert_held(&ci->i_ceph_lock);
+
+	dout("__ceph_remove_cap %p from %p\n", cap, &ci->netfs.inode);
+
+	mdsc = ceph_inode_to_client(&ci->netfs.inode)->mdsc;
+
+	/* remove from inode's cap rbtree, and clear auth cap */
+	rb_erase(&cap->ci_node, &ci->i_caps);
+	if (ci->i_auth_cap == cap)
+		ci->i_auth_cap = NULL;
+
+	/* remove from session list */
+	spin_lock(&session->s_cap_lock);
+	if (session->s_cap_iterator == cap) {
+		/* not yet, we are iterating over this very cap */
+		dout("__ceph_remove_cap  delaying %p removal from session %p\n",
+		     cap, cap->session);
+	} else {
+		list_del_init(&cap->session_caps);
+		session->s_nr_caps--;
+		atomic64_dec(&mdsc->metric.total_caps);
+		cap->session = NULL;
+		removed = 1;
+	}
+	/* protect backpointer with s_cap_lock: see iterate_session_caps */
+	cap->ci = NULL;
+
+	/*
+	 * s_cap_reconnect is protected by s_cap_lock. no one changes
+	 * s_cap_gen while session is in the reconnect state.
+	 */
+	if (queue_release &&
+	    (!session->s_cap_reconnect ||
+	     cap->cap_gen == atomic_read(&session->s_cap_gen))) {
+		cap->queue_release = 1;
+		if (removed) {
+			__ceph_queue_cap_release(session, cap);
+			removed = 0;
+		}
+	} else {
+		cap->queue_release = 0;
+	}
+	cap->cap_ino = ci->i_vino.ino;
+
+	spin_unlock(&session->s_cap_lock);
+
+	if (removed)
+		ceph_put_cap(mdsc, cap);
+
+	if (!__ceph_is_any_real_caps(ci)) {
+		/* when reconnect denied, we remove session caps forcibly,
+		 * i_wr_ref can be non-zero. If there are ongoing write,
+		 * keep i_snap_realm.
+		 */
+		if (ci->i_wr_ref == 0 && ci->i_snap_realm)
+			ceph_change_snap_realm(&ci->netfs.inode, NULL);
+
+		__cap_delay_cancel(mdsc, ci);
+	}
+}
+
+void ceph_remove_cap(struct ceph_cap *cap, bool queue_release)
+{
+	struct ceph_inode_info *ci = cap->ci;
+	struct ceph_fs_client *fsc;
+
+	/* 'ci' being NULL means the remove have already occurred */
+	if (!ci) {
+		dout("%s: cap inode is NULL\n", __func__);
+		return;
+	}
+
+	lockdep_assert_held(&ci->i_ceph_lock);
+
+	fsc = ceph_inode_to_client(&ci->netfs.inode);
+	WARN_ON_ONCE(ci->i_auth_cap == cap &&
+		     !list_empty(&ci->i_dirty_item) &&
+		     !fsc->blocklisted &&
+		     !ceph_inode_is_shutdown(&ci->netfs.inode));
+
+	__ceph_remove_cap(cap, queue_release);
+}
+
+struct cap_msg_args {
+	struct ceph_mds_session	*session;
+	u64			ino, cid, follows;
+	u64			flush_tid, oldest_flush_tid, size, max_size;
+	u64			xattr_version;
+	u64			change_attr;
+	struct ceph_buffer	*xattr_buf;
+	struct ceph_buffer	*old_xattr_buf;
+	struct timespec64	atime, mtime, ctime, btime;
+	int			op, caps, wanted, dirty;
+	u32			seq, issue_seq, mseq, time_warp_seq;
+	u32			flags;
+	kuid_t			uid;
+	kgid_t			gid;
+	umode_t			mode;
+	bool			inline_data;
+	bool			wake;
+};
+
+/*
+ * cap struct size + flock buffer size + inline version + inline data size +
+ * osd_epoch_barrier + oldest_flush_tid
+ */
+#define CAP_MSG_SIZE (sizeof(struct ceph_mds_caps) + \
+		      4 + 8 + 4 + 4 + 8 + 4 + 4 + 4 + 8 + 8 + 4)
+
+/* Marshal up the cap msg to the MDS */
+static void encode_cap_msg(struct ceph_msg *msg, struct cap_msg_args *arg)
+{
+	struct ceph_mds_caps *fc;
+	void *p;
+	struct ceph_osd_client *osdc = &arg->session->s_mdsc->fsc->client->osdc;
+
+	dout("%s %s %llx %llx caps %s wanted %s dirty %s seq %u/%u tid %llu/%llu mseq %u follows %lld size %llu/%llu xattr_ver %llu xattr_len %d\n",
+	     __func__, ceph_cap_op_name(arg->op), arg->cid, arg->ino,
+	     ceph_cap_string(arg->caps), ceph_cap_string(arg->wanted),
+	     ceph_cap_string(arg->dirty), arg->seq, arg->issue_seq,
+	     arg->flush_tid, arg->oldest_flush_tid, arg->mseq, arg->follows,
+	     arg->size, arg->max_size, arg->xattr_version,
+	     arg->xattr_buf ? (int)arg->xattr_buf->vec.iov_len : 0);
+
+	msg->hdr.version = cpu_to_le16(10);
+	msg->hdr.tid = cpu_to_le64(arg->flush_tid);
+
+	fc = msg->front.iov_base;
+	memset(fc, 0, sizeof(*fc));
+
+	fc->cap_id = cpu_to_le64(arg->cid);
+	fc->op = cpu_to_le32(arg->op);
+	fc->seq = cpu_to_le32(arg->seq);
+	fc->issue_seq = cpu_to_le32(arg->issue_seq);
+	fc->migrate_seq = cpu_to_le32(arg->mseq);
+	fc->caps = cpu_to_le32(arg->caps);
+	fc->wanted = cpu_to_le32(arg->wanted);
+	fc->dirty = cpu_to_le32(arg->dirty);
+	fc->ino = cpu_to_le64(arg->ino);
+	fc->snap_follows = cpu_to_le64(arg->follows);
+
+	fc->size = cpu_to_le64(arg->size);
+	fc->max_size = cpu_to_le64(arg->max_size);
+	ceph_encode_timespec64(&fc->mtime, &arg->mtime);
+	ceph_encode_timespec64(&fc->atime, &arg->atime);
+	ceph_encode_timespec64(&fc->ctime, &arg->ctime);
+	fc->time_warp_seq = cpu_to_le32(arg->time_warp_seq);
+
+	fc->uid = cpu_to_le32(from_kuid(&init_user_ns, arg->uid));
+	fc->gid = cpu_to_le32(from_kgid(&init_user_ns, arg->gid));
+	fc->mode = cpu_to_le32(arg->mode);
+
+	fc->xattr_version = cpu_to_le64(arg->xattr_version);
+	if (arg->xattr_buf) {
+		msg->middle = ceph_buffer_get(arg->xattr_buf);
+		fc->xattr_len = cpu_to_le32(arg->xattr_buf->vec.iov_len);
+		msg->hdr.middle_len = cpu_to_le32(arg->xattr_buf->vec.iov_len);
+	}
+
+	p = fc + 1;
+	/* flock buffer size (version 2) */
+	ceph_encode_32(&p, 0);
+	/* inline version (version 4) */
+	ceph_encode_64(&p, arg->inline_data ? 0 : CEPH_INLINE_NONE);
+	/* inline data size */
+	ceph_encode_32(&p, 0);
+	/*
+	 * osd_epoch_barrier (version 5)
+	 * The epoch_barrier is protected osdc->lock, so READ_ONCE here in
+	 * case it was recently changed
+	 */
+	ceph_encode_32(&p, READ_ONCE(osdc->epoch_barrier));
+	/* oldest_flush_tid (version 6) */
+	ceph_encode_64(&p, arg->oldest_flush_tid);
+
+	/*
+	 * caller_uid/caller_gid (version 7)
+	 *
+	 * Currently, we don't properly track which caller dirtied the caps
+	 * last, and force a flush of them when there is a conflict. For now,
+	 * just set this to 0:0, to emulate how the MDS has worked up to now.
+	 */
+	ceph_encode_32(&p, 0);
+	ceph_encode_32(&p, 0);
+
+	/* pool namespace (version 8) (mds always ignores this) */
+	ceph_encode_32(&p, 0);
+
+	/* btime and change_attr (version 9) */
+	ceph_encode_timespec64(p, &arg->btime);
+	p += sizeof(struct ceph_timespec);
+	ceph_encode_64(&p, arg->change_attr);
+
+	/* Advisory flags (version 10) */
+	ceph_encode_32(&p, arg->flags);
+}
+
+/*
+ * Queue cap releases when an inode is dropped from our cache.
+ */
+void __ceph_remove_caps(struct ceph_inode_info *ci)
+{
+	struct rb_node *p;
+
+	/* lock i_ceph_lock, because ceph_d_revalidate(..., LOOKUP_RCU)
+	 * may call __ceph_caps_issued_mask() on a freeing inode. */
+	spin_lock(&ci->i_ceph_lock);
+	p = rb_first(&ci->i_caps);
+	while (p) {
+		struct ceph_cap *cap = rb_entry(p, struct ceph_cap, ci_node);
+		p = rb_next(p);
+		ceph_remove_cap(cap, true);
+	}
+	spin_unlock(&ci->i_ceph_lock);
+}
+
+/*
+ * Prepare to send a cap message to an MDS. Update the cap state, and populate
+ * the arg struct with the parameters that will need to be sent. This should
+ * be done under the i_ceph_lock to guard against changes to cap state.
+ *
+ * Make note of max_size reported/requested from mds, revoked caps
+ * that have now been implemented.
+ */
+static void __prep_cap(struct cap_msg_args *arg, struct ceph_cap *cap,
+		       int op, int flags, int used, int want, int retain,
+		       int flushing, u64 flush_tid, u64 oldest_flush_tid)
+{
+	struct ceph_inode_info *ci = cap->ci;
+	struct inode *inode = &ci->netfs.inode;
+	int held, revoking;
+
+	lockdep_assert_held(&ci->i_ceph_lock);
+
+	held = cap->issued | cap->implemented;
+	revoking = cap->implemented & ~cap->issued;
+	retain &= ~revoking;
+
+	dout("%s %p cap %p session %p %s -> %s (revoking %s)\n",
+	     __func__, inode, cap, cap->session,
+	     ceph_cap_string(held), ceph_cap_string(held & retain),
+	     ceph_cap_string(revoking));
+	BUG_ON((retain & CEPH_CAP_PIN) == 0);
+
+	ci->i_ceph_flags &= ~CEPH_I_FLUSH;
+
+	cap->issued &= retain;  /* drop bits we don't want */
+	/*
+	 * Wake up any waiters on wanted -> needed transition. This is due to
+	 * the weird transition from buffered to sync IO... we need to flush
+	 * dirty pages _before_ allowing sync writes to avoid reordering.
+	 */
+	arg->wake = cap->implemented & ~cap->issued;
+	cap->implemented &= cap->issued | used;
+	cap->mds_wanted = want;
+
+	arg->session = cap->session;
+	arg->ino = ceph_vino(inode).ino;
+	arg->cid = cap->cap_id;
+	arg->follows = flushing ? ci->i_head_snapc->seq : 0;
+	arg->flush_tid = flush_tid;
+	arg->oldest_flush_tid = oldest_flush_tid;
+
+	arg->size = i_size_read(inode);
+	ci->i_reported_size = arg->size;
+	arg->max_size = ci->i_wanted_max_size;
+	if (cap == ci->i_auth_cap) {
+		if (want & CEPH_CAP_ANY_FILE_WR)
+			ci->i_requested_max_size = arg->max_size;
+		else
+			ci->i_requested_max_size = 0;
+	}
+
+	if (flushing & CEPH_CAP_XATTR_EXCL) {
+		arg->old_xattr_buf = __ceph_build_xattrs_blob(ci);
+		arg->xattr_version = ci->i_xattrs.version;
+		arg->xattr_buf = ci->i_xattrs.blob;
+	} else {
+		arg->xattr_buf = NULL;
+		arg->old_xattr_buf = NULL;
+	}
+
+	arg->mtime = inode->i_mtime;
+	arg->atime = inode->i_atime;
+	arg->ctime = inode->i_ctime;
+	arg->btime = ci->i_btime;
+	arg->change_attr = inode_peek_iversion_raw(inode);
+
+	arg->op = op;
+	arg->caps = cap->implemented;
+	arg->wanted = want;
+	arg->dirty = flushing;
+
+	arg->seq = cap->seq;
+	arg->issue_seq = cap->issue_seq;
+	arg->mseq = cap->mseq;
+	arg->time_warp_seq = ci->i_time_warp_seq;
+
+	arg->uid = inode->i_uid;
+	arg->gid = inode->i_gid;
+	arg->mode = inode->i_mode;
+
+	arg->inline_data = ci->i_inline_version != CEPH_INLINE_NONE;
+	if (!(flags & CEPH_CLIENT_CAPS_PENDING_CAPSNAP) &&
+	    !list_empty(&ci->i_cap_snaps)) {
+		struct ceph_cap_snap *capsnap;
+		list_for_each_entry_reverse(capsnap, &ci->i_cap_snaps, ci_item) {
+			if (capsnap->cap_flush.tid)
+				break;
+			if (capsnap->need_flush) {
+				flags |= CEPH_CLIENT_CAPS_PENDING_CAPSNAP;
+				break;
+			}
+		}
+	}
+	arg->flags = flags;
+}
+
+/*
+ * Send a cap msg on the given inode.
+ *
+ * Caller should hold snap_rwsem (read), s_mutex.
+ */
+static void __send_cap(struct cap_msg_args *arg, struct ceph_inode_info *ci)
+{
+	struct ceph_msg *msg;
+	struct inode *inode = &ci->netfs.inode;
+
+	msg = ceph_msg_new(CEPH_MSG_CLIENT_CAPS, CAP_MSG_SIZE, GFP_NOFS, false);
+	if (!msg) {
+		pr_err("error allocating cap msg: ino (%llx.%llx) flushing %s tid %llu, requeuing cap.\n",
+		       ceph_vinop(inode), ceph_cap_string(arg->dirty),
+		       arg->flush_tid);
+		spin_lock(&ci->i_ceph_lock);
+		__cap_delay_requeue(arg->session->s_mdsc, ci);
+		spin_unlock(&ci->i_ceph_lock);
+		return;
+	}
+
+	encode_cap_msg(msg, arg);
+	ceph_con_send(&arg->session->s_con, msg);
+	ceph_buffer_put(arg->old_xattr_buf);
+	if (arg->wake)
+		wake_up_all(&ci->i_cap_wq);
+}
+
+static inline int __send_flush_snap(struct inode *inode,
+				    struct ceph_mds_session *session,
+				    struct ceph_cap_snap *capsnap,
+				    u32 mseq, u64 oldest_flush_tid)
+{
+	struct cap_msg_args	arg;
+	struct ceph_msg		*msg;
+
+	msg = ceph_msg_new(CEPH_MSG_CLIENT_CAPS, CAP_MSG_SIZE, GFP_NOFS, false);
+	if (!msg)
+		return -ENOMEM;
+
+	arg.session = session;
+	arg.ino = ceph_vino(inode).ino;
+	arg.cid = 0;
+	arg.follows = capsnap->follows;
+	arg.flush_tid = capsnap->cap_flush.tid;
+	arg.oldest_flush_tid = oldest_flush_tid;
+
+	arg.size = capsnap->size;
+	arg.max_size = 0;
+	arg.xattr_version = capsnap->xattr_version;
+	arg.xattr_buf = capsnap->xattr_blob;
+	arg.old_xattr_buf = NULL;
+
+	arg.atime = capsnap->atime;
+	arg.mtime = capsnap->mtime;
+	arg.ctime = capsnap->ctime;
+	arg.btime = capsnap->btime;
+	arg.change_attr = capsnap->change_attr;
+
+	arg.op = CEPH_CAP_OP_FLUSHSNAP;
+	arg.caps = capsnap->issued;
+	arg.wanted = 0;
+	arg.dirty = capsnap->dirty;
+
+	arg.seq = 0;
+	arg.issue_seq = 0;
+	arg.mseq = mseq;
+	arg.time_warp_seq = capsnap->time_warp_seq;
+
+	arg.uid = capsnap->uid;
+	arg.gid = capsnap->gid;
+	arg.mode = capsnap->mode;
+
+	arg.inline_data = capsnap->inline_data;
+	arg.flags = 0;
+	arg.wake = false;
+
+	encode_cap_msg(msg, &arg);
+	ceph_con_send(&arg.session->s_con, msg);
+	return 0;
+}
+
+/*
+ * When a snapshot is taken, clients accumulate dirty metadata on
+ * inodes with capabilities in ceph_cap_snaps to describe the file
+ * state at the time the snapshot was taken.  This must be flushed
+ * asynchronously back to the MDS once sync writes complete and dirty
+ * data is written out.
+ *
+ * Called under i_ceph_lock.
+ */
+static void __ceph_flush_snaps(struct ceph_inode_info *ci,
+			       struct ceph_mds_session *session)
+		__releases(ci->i_ceph_lock)
+		__acquires(ci->i_ceph_lock)
+{
+	struct inode *inode = &ci->netfs.inode;
+	struct ceph_mds_client *mdsc = session->s_mdsc;
+	struct ceph_cap_snap *capsnap;
+	u64 oldest_flush_tid = 0;
+	u64 first_tid = 1, last_tid = 0;
+
+	dout("__flush_snaps %p session %p\n", inode, session);
+
+	list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
+		/*
+		 * we need to wait for sync writes to complete and for dirty
+		 * pages to be written out.
+		 */
+		if (capsnap->dirty_pages || capsnap->writing)
+			break;
+
+		/* should be removed by ceph_try_drop_cap_snap() */
+		BUG_ON(!capsnap->need_flush);
+
+		/* only flush each capsnap once */
+		if (capsnap->cap_flush.tid > 0) {
+			dout(" already flushed %p, skipping\n", capsnap);
+			continue;
+		}
+
+		spin_lock(&mdsc->cap_dirty_lock);
+		capsnap->cap_flush.tid = ++mdsc->last_cap_flush_tid;
+		list_add_tail(&capsnap->cap_flush.g_list,
+			      &mdsc->cap_flush_list);
+		if (oldest_flush_tid == 0)
+			oldest_flush_tid = __get_oldest_flush_tid(mdsc);
+		if (list_empty(&ci->i_flushing_item)) {
+			list_add_tail(&ci->i_flushing_item,
+				      &session->s_cap_flushing);
+		}
+		spin_unlock(&mdsc->cap_dirty_lock);
+
+		list_add_tail(&capsnap->cap_flush.i_list,
+			      &ci->i_cap_flush_list);
+
+		if (first_tid == 1)
+			first_tid = capsnap->cap_flush.tid;
+		last_tid = capsnap->cap_flush.tid;
+	}
+
+	ci->i_ceph_flags &= ~CEPH_I_FLUSH_SNAPS;
+
+	while (first_tid <= last_tid) {
+		struct ceph_cap *cap = ci->i_auth_cap;
+		struct ceph_cap_flush *cf = NULL, *iter;
+		int ret;
+
+		if (!(cap && cap->session == session)) {
+			dout("__flush_snaps %p auth cap %p not mds%d, "
+			     "stop\n", inode, cap, session->s_mds);
+			break;
+		}
+
+		ret = -ENOENT;
+		list_for_each_entry(iter, &ci->i_cap_flush_list, i_list) {
+			if (iter->tid >= first_tid) {
+				cf = iter;
+				ret = 0;
+				break;
+			}
+		}
+		if (ret < 0)
+			break;
+
+		first_tid = cf->tid + 1;
+
+		capsnap = container_of(cf, struct ceph_cap_snap, cap_flush);
+		refcount_inc(&capsnap->nref);
+		spin_unlock(&ci->i_ceph_lock);
+
+		dout("__flush_snaps %p capsnap %p tid %llu %s\n",
+		     inode, capsnap, cf->tid, ceph_cap_string(capsnap->dirty));
+
+		ret = __send_flush_snap(inode, session, capsnap, cap->mseq,
+					oldest_flush_tid);
+		if (ret < 0) {
+			pr_err("__flush_snaps: error sending cap flushsnap, "
+			       "ino (%llx.%llx) tid %llu follows %llu\n",
+				ceph_vinop(inode), cf->tid, capsnap->follows);
+		}
+
+		ceph_put_cap_snap(capsnap);
+		spin_lock(&ci->i_ceph_lock);
+	}
+}
+
+void ceph_flush_snaps(struct ceph_inode_info *ci,
+		      struct ceph_mds_session **psession)
+{
+	struct inode *inode = &ci->netfs.inode;
+	struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;
+	struct ceph_mds_session *session = NULL;
+	bool need_put = false;
+	int mds;
+
+	dout("ceph_flush_snaps %p\n", inode);
+	if (psession)
+		session = *psession;
+retry:
+	spin_lock(&ci->i_ceph_lock);
+	if (!(ci->i_ceph_flags & CEPH_I_FLUSH_SNAPS)) {
+		dout(" no capsnap needs flush, doing nothing\n");
+		goto out;
+	}
+	if (!ci->i_auth_cap) {
+		dout(" no auth cap (migrating?), doing nothing\n");
+		goto out;
+	}
+
+	mds = ci->i_auth_cap->session->s_mds;
+	if (session && session->s_mds != mds) {
+		dout(" oops, wrong session %p mutex\n", session);
+		ceph_put_mds_session(session);
+		session = NULL;
+	}
+	if (!session) {
+		spin_unlock(&ci->i_ceph_lock);
+		mutex_lock(&mdsc->mutex);
+		session = __ceph_lookup_mds_session(mdsc, mds);
+		mutex_unlock(&mdsc->mutex);
+		goto retry;
+	}
+
+	// make sure flushsnap messages are sent in proper order.
+	if (ci->i_ceph_flags & CEPH_I_KICK_FLUSH)
+		__kick_flushing_caps(mdsc, session, ci, 0);
+
+	__ceph_flush_snaps(ci, session);
+out:
+	spin_unlock(&ci->i_ceph_lock);
+
+	if (psession)
+		*psession = session;
+	else
+		ceph_put_mds_session(session);
+	/* we flushed them all; remove this inode from the queue */
+	spin_lock(&mdsc->snap_flush_lock);
+	if (!list_empty(&ci->i_snap_flush_item))
+		need_put = true;
+	list_del_init(&ci->i_snap_flush_item);
+	spin_unlock(&mdsc->snap_flush_lock);
+
+	if (need_put)
+		iput(inode);
+}
+
+/*
+ * Mark caps dirty.  If inode is newly dirty, return the dirty flags.
+ * Caller is then responsible for calling __mark_inode_dirty with the
+ * returned flags value.
+ */
+int __ceph_mark_dirty_caps(struct ceph_inode_info *ci, int mask,
+			   struct ceph_cap_flush **pcf)
+{
+	struct ceph_mds_client *mdsc =
+		ceph_sb_to_client(ci->netfs.inode.i_sb)->mdsc;
+	struct inode *inode = &ci->netfs.inode;
+	int was = ci->i_dirty_caps;
+	int dirty = 0;
+
+	lockdep_assert_held(&ci->i_ceph_lock);
+
+	if (!ci->i_auth_cap) {
+		pr_warn("__mark_dirty_caps %p %llx mask %s, "
+			"but no auth cap (session was closed?)\n",
+			inode, ceph_ino(inode), ceph_cap_string(mask));
+		return 0;
+	}
+
+	dout("__mark_dirty_caps %p %s dirty %s -> %s\n", &ci->netfs.inode,
+	     ceph_cap_string(mask), ceph_cap_string(was),
+	     ceph_cap_string(was | mask));
+	ci->i_dirty_caps |= mask;
+	if (was == 0) {
+		struct ceph_mds_session *session = ci->i_auth_cap->session;
+
+		WARN_ON_ONCE(ci->i_prealloc_cap_flush);
+		swap(ci->i_prealloc_cap_flush, *pcf);
+
+		if (!ci->i_head_snapc) {
+			WARN_ON_ONCE(!rwsem_is_locked(&mdsc->snap_rwsem));
+			ci->i_head_snapc = ceph_get_snap_context(
+				ci->i_snap_realm->cached_context);
+		}
+		dout(" inode %p now dirty snapc %p auth cap %p\n",
+		     &ci->netfs.inode, ci->i_head_snapc, ci->i_auth_cap);
+		BUG_ON(!list_empty(&ci->i_dirty_item));
+		spin_lock(&mdsc->cap_dirty_lock);
+		list_add(&ci->i_dirty_item, &session->s_cap_dirty);
+		spin_unlock(&mdsc->cap_dirty_lock);
+		if (ci->i_flushing_caps == 0) {
+			ihold(inode);
+			dirty |= I_DIRTY_SYNC;
+		}
+	} else {
+		WARN_ON_ONCE(!ci->i_prealloc_cap_flush);
+	}
+	BUG_ON(list_empty(&ci->i_dirty_item));
+	if (((was | ci->i_flushing_caps) & CEPH_CAP_FILE_BUFFER) &&
+	    (mask & CEPH_CAP_FILE_BUFFER))
+		dirty |= I_DIRTY_DATASYNC;
+	__cap_delay_requeue(mdsc, ci);
+	return dirty;
+}
+
+struct ceph_cap_flush *ceph_alloc_cap_flush(void)
+{
+	struct ceph_cap_flush *cf;
+
+	cf = kmem_cache_alloc(ceph_cap_flush_cachep, GFP_KERNEL);
+	if (!cf)
+		return NULL;
+
+	cf->is_capsnap = false;
+	return cf;
+}
+
+void ceph_free_cap_flush(struct ceph_cap_flush *cf)
+{
+	if (cf)
+		kmem_cache_free(ceph_cap_flush_cachep, cf);
+}
+
+static u64 __get_oldest_flush_tid(struct ceph_mds_client *mdsc)
+{
+	if (!list_empty(&mdsc->cap_flush_list)) {
+		struct ceph_cap_flush *cf =
+			list_first_entry(&mdsc->cap_flush_list,
+					 struct ceph_cap_flush, g_list);
+		return cf->tid;
+	}
+	return 0;
+}
+
+/*
+ * Remove cap_flush from the mdsc's or inode's flushing cap list.
+ * Return true if caller needs to wake up flush waiters.
+ */
+static bool __detach_cap_flush_from_mdsc(struct ceph_mds_client *mdsc,
+					 struct ceph_cap_flush *cf)
+{
+	struct ceph_cap_flush *prev;
+	bool wake = cf->wake;
+
+	if (wake && cf->g_list.prev != &mdsc->cap_flush_list) {
+		prev = list_prev_entry(cf, g_list);
+		prev->wake = true;
+		wake = false;
+	}
+	list_del_init(&cf->g_list);
+	return wake;
+}
+
+static bool __detach_cap_flush_from_ci(struct ceph_inode_info *ci,
+				       struct ceph_cap_flush *cf)
+{
+	struct ceph_cap_flush *prev;
+	bool wake = cf->wake;
+
+	if (wake && cf->i_list.prev != &ci->i_cap_flush_list) {
+		prev = list_prev_entry(cf, i_list);
+		prev->wake = true;
+		wake = false;
+	}
+	list_del_init(&cf->i_list);
+	return wake;
+}
+
+/*
+ * Add dirty inode to the flushing list.  Assigned a seq number so we
+ * can wait for caps to flush without starving.
+ *
+ * Called under i_ceph_lock. Returns the flush tid.
+ */
+static u64 __mark_caps_flushing(struct inode *inode,
+				struct ceph_mds_session *session, bool wake,
+				u64 *oldest_flush_tid)
+{
+	struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_cap_flush *cf = NULL;
+	int flushing;
+
+	lockdep_assert_held(&ci->i_ceph_lock);
+	BUG_ON(ci->i_dirty_caps == 0);
+	BUG_ON(list_empty(&ci->i_dirty_item));
+	BUG_ON(!ci->i_prealloc_cap_flush);
+
+	flushing = ci->i_dirty_caps;
+	dout("__mark_caps_flushing flushing %s, flushing_caps %s -> %s\n",
+	     ceph_cap_string(flushing),
+	     ceph_cap_string(ci->i_flushing_caps),
+	     ceph_cap_string(ci->i_flushing_caps | flushing));
+	ci->i_flushing_caps |= flushing;
+	ci->i_dirty_caps = 0;
+	dout(" inode %p now !dirty\n", inode);
+
+	swap(cf, ci->i_prealloc_cap_flush);
+	cf->caps = flushing;
+	cf->wake = wake;
+
+	spin_lock(&mdsc->cap_dirty_lock);
+	list_del_init(&ci->i_dirty_item);
+
+	cf->tid = ++mdsc->last_cap_flush_tid;
+	list_add_tail(&cf->g_list, &mdsc->cap_flush_list);
+	*oldest_flush_tid = __get_oldest_flush_tid(mdsc);
+
+	if (list_empty(&ci->i_flushing_item)) {
+		list_add_tail(&ci->i_flushing_item, &session->s_cap_flushing);
+		mdsc->num_cap_flushing++;
+	}
+	spin_unlock(&mdsc->cap_dirty_lock);
+
+	list_add_tail(&cf->i_list, &ci->i_cap_flush_list);
+
+	return cf->tid;
+}
+
+/*
+ * try to invalidate mapping pages without blocking.
+ */
+static int try_nonblocking_invalidate(struct inode *inode)
+	__releases(ci->i_ceph_lock)
+	__acquires(ci->i_ceph_lock)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	u32 invalidating_gen = ci->i_rdcache_gen;
+
+	spin_unlock(&ci->i_ceph_lock);
+	ceph_fscache_invalidate(inode, false);
+	invalidate_mapping_pages(&inode->i_data, 0, -1);
+	spin_lock(&ci->i_ceph_lock);
+
+	if (inode->i_data.nrpages == 0 &&
+	    invalidating_gen == ci->i_rdcache_gen) {
+		/* success. */
+		dout("try_nonblocking_invalidate %p success\n", inode);
+		/* save any racing async invalidate some trouble */
+		ci->i_rdcache_revoking = ci->i_rdcache_gen - 1;
+		return 0;
+	}
+	dout("try_nonblocking_invalidate %p failed\n", inode);
+	return -1;
+}
+
+bool __ceph_should_report_size(struct ceph_inode_info *ci)
+{
+	loff_t size = i_size_read(&ci->netfs.inode);
+	/* mds will adjust max size according to the reported size */
+	if (ci->i_flushing_caps & CEPH_CAP_FILE_WR)
+		return false;
+	if (size >= ci->i_max_size)
+		return true;
+	/* half of previous max_size increment has been used */
+	if (ci->i_max_size > ci->i_reported_size &&
+	    (size << 1) >= ci->i_max_size + ci->i_reported_size)
+		return true;
+	return false;
+}
+
+/*
+ * Swiss army knife function to examine currently used and wanted
+ * versus held caps.  Release, flush, ack revoked caps to mds as
+ * appropriate.
+ *
+ *  CHECK_CAPS_AUTHONLY - we should only check the auth cap
+ *  CHECK_CAPS_FLUSH - we should flush any dirty caps immediately, without
+ *    further delay.
+ */
+void ceph_check_caps(struct ceph_inode_info *ci, int flags,
+		     struct ceph_mds_session *session)
+{
+	struct inode *inode = &ci->netfs.inode;
+	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(inode->i_sb);
+	struct ceph_cap *cap;
+	u64 flush_tid, oldest_flush_tid;
+	int file_wanted, used, cap_used;
+	int issued, implemented, want, retain, revoking, flushing = 0;
+	int mds = -1;   /* keep track of how far we've gone through i_caps list
+			   to avoid an infinite loop on retry */
+	struct rb_node *p;
+	bool queue_invalidate = false;
+	bool tried_invalidate = false;
+	bool queue_writeback = false;
+
+	if (session)
+		ceph_get_mds_session(session);
+
+	spin_lock(&ci->i_ceph_lock);
+	if (ci->i_ceph_flags & CEPH_I_ASYNC_CREATE) {
+		/* Don't send messages until we get async create reply */
+		spin_unlock(&ci->i_ceph_lock);
+		ceph_put_mds_session(session);
+		return;
+	}
+
+	if (ci->i_ceph_flags & CEPH_I_FLUSH)
+		flags |= CHECK_CAPS_FLUSH;
+retry:
+	/* Caps wanted by virtue of active open files. */
+	file_wanted = __ceph_caps_file_wanted(ci);
+
+	/* Caps which have active references against them */
+	used = __ceph_caps_used(ci);
+
+	/*
+	 * "issued" represents the current caps that the MDS wants us to have.
+	 * "implemented" is the set that we have been granted, and includes the
+	 * ones that have not yet been returned to the MDS (the "revoking" set,
+	 * usually because they have outstanding references).
+	 */
+	issued = __ceph_caps_issued(ci, &implemented);
+	revoking = implemented & ~issued;
+
+	want = file_wanted;
+
+	/* The ones we currently want to retain (may be adjusted below) */
+	retain = file_wanted | used | CEPH_CAP_PIN;
+	if (!mdsc->stopping && inode->i_nlink > 0) {
+		if (file_wanted) {
+			retain |= CEPH_CAP_ANY;       /* be greedy */
+		} else if (S_ISDIR(inode->i_mode) &&
+			   (issued & CEPH_CAP_FILE_SHARED) &&
+			   __ceph_dir_is_complete(ci)) {
+			/*
+			 * If a directory is complete, we want to keep
+			 * the exclusive cap. So that MDS does not end up
+			 * revoking the shared cap on every create/unlink
+			 * operation.
+			 */
+			if (IS_RDONLY(inode)) {
+				want = CEPH_CAP_ANY_SHARED;
+			} else {
+				want |= CEPH_CAP_ANY_SHARED | CEPH_CAP_FILE_EXCL;
+			}
+			retain |= want;
+		} else {
+
+			retain |= CEPH_CAP_ANY_SHARED;
+			/*
+			 * keep RD only if we didn't have the file open RW,
+			 * because then the mds would revoke it anyway to
+			 * journal max_size=0.
+			 */
+			if (ci->i_max_size == 0)
+				retain |= CEPH_CAP_ANY_RD;
+		}
+	}
+
+	dout("check_caps %llx.%llx file_want %s used %s dirty %s flushing %s"
+	     " issued %s revoking %s retain %s %s%s%s\n", ceph_vinop(inode),
+	     ceph_cap_string(file_wanted),
+	     ceph_cap_string(used), ceph_cap_string(ci->i_dirty_caps),
+	     ceph_cap_string(ci->i_flushing_caps),
+	     ceph_cap_string(issued), ceph_cap_string(revoking),
+	     ceph_cap_string(retain),
+	     (flags & CHECK_CAPS_AUTHONLY) ? " AUTHONLY" : "",
+	     (flags & CHECK_CAPS_FLUSH) ? " FLUSH" : "",
+	     (flags & CHECK_CAPS_NOINVAL) ? " NOINVAL" : "");
+
+	/*
+	 * If we no longer need to hold onto old our caps, and we may
+	 * have cached pages, but don't want them, then try to invalidate.
+	 * If we fail, it's because pages are locked.... try again later.
+	 */
+	if ((!(flags & CHECK_CAPS_NOINVAL) || mdsc->stopping) &&
+	    S_ISREG(inode->i_mode) &&
+	    !(ci->i_wb_ref || ci->i_wrbuffer_ref) &&   /* no dirty pages... */
+	    inode->i_data.nrpages &&		/* have cached pages */
+	    (revoking & (CEPH_CAP_FILE_CACHE|
+			 CEPH_CAP_FILE_LAZYIO)) && /*  or revoking cache */
+	    !tried_invalidate) {
+		dout("check_caps trying to invalidate on %llx.%llx\n",
+		     ceph_vinop(inode));
+		if (try_nonblocking_invalidate(inode) < 0) {
+			dout("check_caps queuing invalidate\n");
+			queue_invalidate = true;
+			ci->i_rdcache_revoking = ci->i_rdcache_gen;
+		}
+		tried_invalidate = true;
+		goto retry;
+	}
+
+	for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
+		int mflags = 0;
+		struct cap_msg_args arg;
+
+		cap = rb_entry(p, struct ceph_cap, ci_node);
+
+		/* avoid looping forever */
+		if (mds >= cap->mds ||
+		    ((flags & CHECK_CAPS_AUTHONLY) && cap != ci->i_auth_cap))
+			continue;
+
+		/*
+		 * If we have an auth cap, we don't need to consider any
+		 * overlapping caps as used.
+		 */
+		cap_used = used;
+		if (ci->i_auth_cap && cap != ci->i_auth_cap)
+			cap_used &= ~ci->i_auth_cap->issued;
+
+		revoking = cap->implemented & ~cap->issued;
+		dout(" mds%d cap %p used %s issued %s implemented %s revoking %s\n",
+		     cap->mds, cap, ceph_cap_string(cap_used),
+		     ceph_cap_string(cap->issued),
+		     ceph_cap_string(cap->implemented),
+		     ceph_cap_string(revoking));
+
+		if (cap == ci->i_auth_cap &&
+		    (cap->issued & CEPH_CAP_FILE_WR)) {
+			/* request larger max_size from MDS? */
+			if (ci->i_wanted_max_size > ci->i_max_size &&
+			    ci->i_wanted_max_size > ci->i_requested_max_size) {
+				dout("requesting new max_size\n");
+				goto ack;
+			}
+
+			/* approaching file_max? */
+			if (__ceph_should_report_size(ci)) {
+				dout("i_size approaching max_size\n");
+				goto ack;
+			}
+		}
+		/* flush anything dirty? */
+		if (cap == ci->i_auth_cap) {
+			if ((flags & CHECK_CAPS_FLUSH) && ci->i_dirty_caps) {
+				dout("flushing dirty caps\n");
+				goto ack;
+			}
+			if (ci->i_ceph_flags & CEPH_I_FLUSH_SNAPS) {
+				dout("flushing snap caps\n");
+				goto ack;
+			}
+		}
+
+		/* completed revocation? going down and there are no caps? */
+		if (revoking) {
+			if ((revoking & cap_used) == 0) {
+				dout("completed revocation of %s\n",
+				      ceph_cap_string(cap->implemented & ~cap->issued));
+				goto ack;
+			}
+
+			/*
+			 * If the "i_wrbuffer_ref" was increased by mmap or generic
+			 * cache write just before the ceph_check_caps() is called,
+			 * the Fb capability revoking will fail this time. Then we
+			 * must wait for the BDI's delayed work to flush the dirty
+			 * pages and to release the "i_wrbuffer_ref", which will cost
+			 * at most 5 seconds. That means the MDS needs to wait at
+			 * most 5 seconds to finished the Fb capability's revocation.
+			 *
+			 * Let's queue a writeback for it.
+			 */
+			if (S_ISREG(inode->i_mode) && ci->i_wrbuffer_ref &&
+			    (revoking & CEPH_CAP_FILE_BUFFER))
+				queue_writeback = true;
+		}
+
+		/* want more caps from mds? */
+		if (want & ~cap->mds_wanted) {
+			if (want & ~(cap->mds_wanted | cap->issued))
+				goto ack;
+			if (!__cap_is_valid(cap))
+				goto ack;
+		}
+
+		/* things we might delay */
+		if ((cap->issued & ~retain) == 0)
+			continue;     /* nope, all good */
+
+ack:
+		ceph_put_mds_session(session);
+		session = ceph_get_mds_session(cap->session);
+
+		/* kick flushing and flush snaps before sending normal
+		 * cap message */
+		if (cap == ci->i_auth_cap &&
+		    (ci->i_ceph_flags &
+		     (CEPH_I_KICK_FLUSH | CEPH_I_FLUSH_SNAPS))) {
+			if (ci->i_ceph_flags & CEPH_I_KICK_FLUSH)
+				__kick_flushing_caps(mdsc, session, ci, 0);
+			if (ci->i_ceph_flags & CEPH_I_FLUSH_SNAPS)
+				__ceph_flush_snaps(ci, session);
+
+			goto retry;
+		}
+
+		if (cap == ci->i_auth_cap && ci->i_dirty_caps) {
+			flushing = ci->i_dirty_caps;
+			flush_tid = __mark_caps_flushing(inode, session, false,
+							 &oldest_flush_tid);
+			if (flags & CHECK_CAPS_FLUSH &&
+			    list_empty(&session->s_cap_dirty))
+				mflags |= CEPH_CLIENT_CAPS_SYNC;
+		} else {
+			flushing = 0;
+			flush_tid = 0;
+			spin_lock(&mdsc->cap_dirty_lock);
+			oldest_flush_tid = __get_oldest_flush_tid(mdsc);
+			spin_unlock(&mdsc->cap_dirty_lock);
+		}
+
+		mds = cap->mds;  /* remember mds, so we don't repeat */
+
+		__prep_cap(&arg, cap, CEPH_CAP_OP_UPDATE, mflags, cap_used,
+			   want, retain, flushing, flush_tid, oldest_flush_tid);
+
+		spin_unlock(&ci->i_ceph_lock);
+		__send_cap(&arg, ci);
+		spin_lock(&ci->i_ceph_lock);
+
+		goto retry; /* retake i_ceph_lock and restart our cap scan. */
+	}
+
+	/* periodically re-calculate caps wanted by open files */
+	if (__ceph_is_any_real_caps(ci) &&
+	    list_empty(&ci->i_cap_delay_list) &&
+	    (file_wanted & ~CEPH_CAP_PIN) &&
+	    !(used & (CEPH_CAP_FILE_RD | CEPH_CAP_ANY_FILE_WR))) {
+		__cap_delay_requeue(mdsc, ci);
+	}
+
+	spin_unlock(&ci->i_ceph_lock);
+
+	ceph_put_mds_session(session);
+	if (queue_writeback)
+		ceph_queue_writeback(inode);
+	if (queue_invalidate)
+		ceph_queue_invalidate(inode);
+}
+
+/*
+ * Try to flush dirty caps back to the auth mds.
+ */
+static int try_flush_caps(struct inode *inode, u64 *ptid)
+{
+	struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	int flushing = 0;
+	u64 flush_tid = 0, oldest_flush_tid = 0;
+
+	spin_lock(&ci->i_ceph_lock);
+retry_locked:
+	if (ci->i_dirty_caps && ci->i_auth_cap) {
+		struct ceph_cap *cap = ci->i_auth_cap;
+		struct cap_msg_args arg;
+		struct ceph_mds_session *session = cap->session;
+
+		if (session->s_state < CEPH_MDS_SESSION_OPEN) {
+			spin_unlock(&ci->i_ceph_lock);
+			goto out;
+		}
+
+		if (ci->i_ceph_flags &
+		    (CEPH_I_KICK_FLUSH | CEPH_I_FLUSH_SNAPS)) {
+			if (ci->i_ceph_flags & CEPH_I_KICK_FLUSH)
+				__kick_flushing_caps(mdsc, session, ci, 0);
+			if (ci->i_ceph_flags & CEPH_I_FLUSH_SNAPS)
+				__ceph_flush_snaps(ci, session);
+			goto retry_locked;
+		}
+
+		flushing = ci->i_dirty_caps;
+		flush_tid = __mark_caps_flushing(inode, session, true,
+						 &oldest_flush_tid);
+
+		__prep_cap(&arg, cap, CEPH_CAP_OP_FLUSH, CEPH_CLIENT_CAPS_SYNC,
+			   __ceph_caps_used(ci), __ceph_caps_wanted(ci),
+			   (cap->issued | cap->implemented),
+			   flushing, flush_tid, oldest_flush_tid);
+		spin_unlock(&ci->i_ceph_lock);
+
+		__send_cap(&arg, ci);
+	} else {
+		if (!list_empty(&ci->i_cap_flush_list)) {
+			struct ceph_cap_flush *cf =
+				list_last_entry(&ci->i_cap_flush_list,
+						struct ceph_cap_flush, i_list);
+			cf->wake = true;
+			flush_tid = cf->tid;
+		}
+		flushing = ci->i_flushing_caps;
+		spin_unlock(&ci->i_ceph_lock);
+	}
+out:
+	*ptid = flush_tid;
+	return flushing;
+}
+
+/*
+ * Return true if we've flushed caps through the given flush_tid.
+ */
+static int caps_are_flushed(struct inode *inode, u64 flush_tid)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	int ret = 1;
+
+	spin_lock(&ci->i_ceph_lock);
+	if (!list_empty(&ci->i_cap_flush_list)) {
+		struct ceph_cap_flush * cf =
+			list_first_entry(&ci->i_cap_flush_list,
+					 struct ceph_cap_flush, i_list);
+		if (cf->tid <= flush_tid)
+			ret = 0;
+	}
+	spin_unlock(&ci->i_ceph_lock);
+	return ret;
+}
+
+/*
+ * flush the mdlog and wait for any unsafe requests to complete.
+ */
+static int flush_mdlog_and_wait_inode_unsafe_requests(struct inode *inode)
+{
+	struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_mds_request *req1 = NULL, *req2 = NULL;
+	int ret, err = 0;
+
+	spin_lock(&ci->i_unsafe_lock);
+	if (S_ISDIR(inode->i_mode) && !list_empty(&ci->i_unsafe_dirops)) {
+		req1 = list_last_entry(&ci->i_unsafe_dirops,
+					struct ceph_mds_request,
+					r_unsafe_dir_item);
+		ceph_mdsc_get_request(req1);
+	}
+	if (!list_empty(&ci->i_unsafe_iops)) {
+		req2 = list_last_entry(&ci->i_unsafe_iops,
+					struct ceph_mds_request,
+					r_unsafe_target_item);
+		ceph_mdsc_get_request(req2);
+	}
+	spin_unlock(&ci->i_unsafe_lock);
+
+	/*
+	 * Trigger to flush the journal logs in all the relevant MDSes
+	 * manually, or in the worst case we must wait at most 5 seconds
+	 * to wait the journal logs to be flushed by the MDSes periodically.
+	 */
+	if (req1 || req2) {
+		struct ceph_mds_request *req;
+		struct ceph_mds_session **sessions;
+		struct ceph_mds_session *s;
+		unsigned int max_sessions;
+		int i;
+
+		mutex_lock(&mdsc->mutex);
+		max_sessions = mdsc->max_sessions;
+
+		sessions = kcalloc(max_sessions, sizeof(s), GFP_KERNEL);
+		if (!sessions) {
+			mutex_unlock(&mdsc->mutex);
+			err = -ENOMEM;
+			goto out;
+		}
+
+		spin_lock(&ci->i_unsafe_lock);
+		if (req1) {
+			list_for_each_entry(req, &ci->i_unsafe_dirops,
+					    r_unsafe_dir_item) {
+				s = req->r_session;
+				if (!s)
+					continue;
+				if (!sessions[s->s_mds]) {
+					s = ceph_get_mds_session(s);
+					sessions[s->s_mds] = s;
+				}
+			}
+		}
+		if (req2) {
+			list_for_each_entry(req, &ci->i_unsafe_iops,
+					    r_unsafe_target_item) {
+				s = req->r_session;
+				if (!s)
+					continue;
+				if (!sessions[s->s_mds]) {
+					s = ceph_get_mds_session(s);
+					sessions[s->s_mds] = s;
+				}
+			}
+		}
+		spin_unlock(&ci->i_unsafe_lock);
+
+		/* the auth MDS */
+		spin_lock(&ci->i_ceph_lock);
+		if (ci->i_auth_cap) {
+			s = ci->i_auth_cap->session;
+			if (!sessions[s->s_mds])
+				sessions[s->s_mds] = ceph_get_mds_session(s);
+		}
+		spin_unlock(&ci->i_ceph_lock);
+		mutex_unlock(&mdsc->mutex);
+
+		/* send flush mdlog request to MDSes */
+		for (i = 0; i < max_sessions; i++) {
+			s = sessions[i];
+			if (s) {
+				send_flush_mdlog(s);
+				ceph_put_mds_session(s);
+			}
+		}
+		kfree(sessions);
+	}
+
+	dout("%s %p wait on tid %llu %llu\n", __func__,
+	     inode, req1 ? req1->r_tid : 0ULL, req2 ? req2->r_tid : 0ULL);
+	if (req1) {
+		ret = !wait_for_completion_timeout(&req1->r_safe_completion,
+					ceph_timeout_jiffies(req1->r_timeout));
+		if (ret)
+			err = -EIO;
+	}
+	if (req2) {
+		ret = !wait_for_completion_timeout(&req2->r_safe_completion,
+					ceph_timeout_jiffies(req2->r_timeout));
+		if (ret)
+			err = -EIO;
+	}
+
+out:
+	if (req1)
+		ceph_mdsc_put_request(req1);
+	if (req2)
+		ceph_mdsc_put_request(req2);
+	return err;
+}
+
+int ceph_fsync(struct file *file, loff_t start, loff_t end, int datasync)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	u64 flush_tid;
+	int ret, err;
+	int dirty;
+
+	dout("fsync %p%s\n", inode, datasync ? " datasync" : "");
+
+	ret = file_write_and_wait_range(file, start, end);
+	if (datasync)
+		goto out;
+
+	ret = ceph_wait_on_async_create(inode);
+	if (ret)
+		goto out;
+
+	dirty = try_flush_caps(inode, &flush_tid);
+	dout("fsync dirty caps are %s\n", ceph_cap_string(dirty));
+
+	err = flush_mdlog_and_wait_inode_unsafe_requests(inode);
+
+	/*
+	 * only wait on non-file metadata writeback (the mds
+	 * can recover size and mtime, so we don't need to
+	 * wait for that)
+	 */
+	if (!err && (dirty & ~CEPH_CAP_ANY_FILE_WR)) {
+		err = wait_event_interruptible(ci->i_cap_wq,
+					caps_are_flushed(inode, flush_tid));
+	}
+
+	if (err < 0)
+		ret = err;
+
+	err = file_check_and_advance_wb_err(file);
+	if (err < 0)
+		ret = err;
+out:
+	dout("fsync %p%s result=%d\n", inode, datasync ? " datasync" : "", ret);
+	return ret;
+}
+
+/*
+ * Flush any dirty caps back to the mds.  If we aren't asked to wait,
+ * queue inode for flush but don't do so immediately, because we can
+ * get by with fewer MDS messages if we wait for data writeback to
+ * complete first.
+ */
+int ceph_write_inode(struct inode *inode, struct writeback_control *wbc)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	u64 flush_tid;
+	int err = 0;
+	int dirty;
+	int wait = (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync);
+
+	dout("write_inode %p wait=%d\n", inode, wait);
+	ceph_fscache_unpin_writeback(inode, wbc);
+	if (wait) {
+		err = ceph_wait_on_async_create(inode);
+		if (err)
+			return err;
+		dirty = try_flush_caps(inode, &flush_tid);
+		if (dirty)
+			err = wait_event_interruptible(ci->i_cap_wq,
+				       caps_are_flushed(inode, flush_tid));
+	} else {
+		struct ceph_mds_client *mdsc =
+			ceph_sb_to_client(inode->i_sb)->mdsc;
+
+		spin_lock(&ci->i_ceph_lock);
+		if (__ceph_caps_dirty(ci))
+			__cap_delay_requeue_front(mdsc, ci);
+		spin_unlock(&ci->i_ceph_lock);
+	}
+	return err;
+}
+
+static void __kick_flushing_caps(struct ceph_mds_client *mdsc,
+				 struct ceph_mds_session *session,
+				 struct ceph_inode_info *ci,
+				 u64 oldest_flush_tid)
+	__releases(ci->i_ceph_lock)
+	__acquires(ci->i_ceph_lock)
+{
+	struct inode *inode = &ci->netfs.inode;
+	struct ceph_cap *cap;
+	struct ceph_cap_flush *cf;
+	int ret;
+	u64 first_tid = 0;
+	u64 last_snap_flush = 0;
+
+	/* Don't do anything until create reply comes in */
+	if (ci->i_ceph_flags & CEPH_I_ASYNC_CREATE)
+		return;
+
+	ci->i_ceph_flags &= ~CEPH_I_KICK_FLUSH;
+
+	list_for_each_entry_reverse(cf, &ci->i_cap_flush_list, i_list) {
+		if (cf->is_capsnap) {
+			last_snap_flush = cf->tid;
+			break;
+		}
+	}
+
+	list_for_each_entry(cf, &ci->i_cap_flush_list, i_list) {
+		if (cf->tid < first_tid)
+			continue;
+
+		cap = ci->i_auth_cap;
+		if (!(cap && cap->session == session)) {
+			pr_err("%p auth cap %p not mds%d ???\n",
+			       inode, cap, session->s_mds);
+			break;
+		}
+
+		first_tid = cf->tid + 1;
+
+		if (!cf->is_capsnap) {
+			struct cap_msg_args arg;
+
+			dout("kick_flushing_caps %p cap %p tid %llu %s\n",
+			     inode, cap, cf->tid, ceph_cap_string(cf->caps));
+			__prep_cap(&arg, cap, CEPH_CAP_OP_FLUSH,
+					 (cf->tid < last_snap_flush ?
+					  CEPH_CLIENT_CAPS_PENDING_CAPSNAP : 0),
+					  __ceph_caps_used(ci),
+					  __ceph_caps_wanted(ci),
+					  (cap->issued | cap->implemented),
+					  cf->caps, cf->tid, oldest_flush_tid);
+			spin_unlock(&ci->i_ceph_lock);
+			__send_cap(&arg, ci);
+		} else {
+			struct ceph_cap_snap *capsnap =
+					container_of(cf, struct ceph_cap_snap,
+						    cap_flush);
+			dout("kick_flushing_caps %p capsnap %p tid %llu %s\n",
+			     inode, capsnap, cf->tid,
+			     ceph_cap_string(capsnap->dirty));
+
+			refcount_inc(&capsnap->nref);
+			spin_unlock(&ci->i_ceph_lock);
+
+			ret = __send_flush_snap(inode, session, capsnap, cap->mseq,
+						oldest_flush_tid);
+			if (ret < 0) {
+				pr_err("kick_flushing_caps: error sending "
+					"cap flushsnap, ino (%llx.%llx) "
+					"tid %llu follows %llu\n",
+					ceph_vinop(inode), cf->tid,
+					capsnap->follows);
+			}
+
+			ceph_put_cap_snap(capsnap);
+		}
+
+		spin_lock(&ci->i_ceph_lock);
+	}
+}
+
+void ceph_early_kick_flushing_caps(struct ceph_mds_client *mdsc,
+				   struct ceph_mds_session *session)
+{
+	struct ceph_inode_info *ci;
+	struct ceph_cap *cap;
+	u64 oldest_flush_tid;
+
+	dout("early_kick_flushing_caps mds%d\n", session->s_mds);
+
+	spin_lock(&mdsc->cap_dirty_lock);
+	oldest_flush_tid = __get_oldest_flush_tid(mdsc);
+	spin_unlock(&mdsc->cap_dirty_lock);
+
+	list_for_each_entry(ci, &session->s_cap_flushing, i_flushing_item) {
+		spin_lock(&ci->i_ceph_lock);
+		cap = ci->i_auth_cap;
+		if (!(cap && cap->session == session)) {
+			pr_err("%p auth cap %p not mds%d ???\n",
+				&ci->netfs.inode, cap, session->s_mds);
+			spin_unlock(&ci->i_ceph_lock);
+			continue;
+		}
+
+
+		/*
+		 * if flushing caps were revoked, we re-send the cap flush
+		 * in client reconnect stage. This guarantees MDS * processes
+		 * the cap flush message before issuing the flushing caps to
+		 * other client.
+		 */
+		if ((cap->issued & ci->i_flushing_caps) !=
+		    ci->i_flushing_caps) {
+			/* encode_caps_cb() also will reset these sequence
+			 * numbers. make sure sequence numbers in cap flush
+			 * message match later reconnect message */
+			cap->seq = 0;
+			cap->issue_seq = 0;
+			cap->mseq = 0;
+			__kick_flushing_caps(mdsc, session, ci,
+					     oldest_flush_tid);
+		} else {
+			ci->i_ceph_flags |= CEPH_I_KICK_FLUSH;
+		}
+
+		spin_unlock(&ci->i_ceph_lock);
+	}
+}
+
+void ceph_kick_flushing_caps(struct ceph_mds_client *mdsc,
+			     struct ceph_mds_session *session)
+{
+	struct ceph_inode_info *ci;
+	struct ceph_cap *cap;
+	u64 oldest_flush_tid;
+
+	lockdep_assert_held(&session->s_mutex);
+
+	dout("kick_flushing_caps mds%d\n", session->s_mds);
+
+	spin_lock(&mdsc->cap_dirty_lock);
+	oldest_flush_tid = __get_oldest_flush_tid(mdsc);
+	spin_unlock(&mdsc->cap_dirty_lock);
+
+	list_for_each_entry(ci, &session->s_cap_flushing, i_flushing_item) {
+		spin_lock(&ci->i_ceph_lock);
+		cap = ci->i_auth_cap;
+		if (!(cap && cap->session == session)) {
+			pr_err("%p auth cap %p not mds%d ???\n",
+				&ci->netfs.inode, cap, session->s_mds);
+			spin_unlock(&ci->i_ceph_lock);
+			continue;
+		}
+		if (ci->i_ceph_flags & CEPH_I_KICK_FLUSH) {
+			__kick_flushing_caps(mdsc, session, ci,
+					     oldest_flush_tid);
+		}
+		spin_unlock(&ci->i_ceph_lock);
+	}
+}
+
+void ceph_kick_flushing_inode_caps(struct ceph_mds_session *session,
+				   struct ceph_inode_info *ci)
+{
+	struct ceph_mds_client *mdsc = session->s_mdsc;
+	struct ceph_cap *cap = ci->i_auth_cap;
+
+	lockdep_assert_held(&ci->i_ceph_lock);
+
+	dout("%s %p flushing %s\n", __func__, &ci->netfs.inode,
+	     ceph_cap_string(ci->i_flushing_caps));
+
+	if (!list_empty(&ci->i_cap_flush_list)) {
+		u64 oldest_flush_tid;
+		spin_lock(&mdsc->cap_dirty_lock);
+		list_move_tail(&ci->i_flushing_item,
+			       &cap->session->s_cap_flushing);
+		oldest_flush_tid = __get_oldest_flush_tid(mdsc);
+		spin_unlock(&mdsc->cap_dirty_lock);
+
+		__kick_flushing_caps(mdsc, session, ci, oldest_flush_tid);
+	}
+}
+
+
+/*
+ * Take references to capabilities we hold, so that we don't release
+ * them to the MDS prematurely.
+ */
+void ceph_take_cap_refs(struct ceph_inode_info *ci, int got,
+			    bool snap_rwsem_locked)
+{
+	lockdep_assert_held(&ci->i_ceph_lock);
+
+	if (got & CEPH_CAP_PIN)
+		ci->i_pin_ref++;
+	if (got & CEPH_CAP_FILE_RD)
+		ci->i_rd_ref++;
+	if (got & CEPH_CAP_FILE_CACHE)
+		ci->i_rdcache_ref++;
+	if (got & CEPH_CAP_FILE_EXCL)
+		ci->i_fx_ref++;
+	if (got & CEPH_CAP_FILE_WR) {
+		if (ci->i_wr_ref == 0 && !ci->i_head_snapc) {
+			BUG_ON(!snap_rwsem_locked);
+			ci->i_head_snapc = ceph_get_snap_context(
+					ci->i_snap_realm->cached_context);
+		}
+		ci->i_wr_ref++;
+	}
+	if (got & CEPH_CAP_FILE_BUFFER) {
+		if (ci->i_wb_ref == 0)
+			ihold(&ci->netfs.inode);
+		ci->i_wb_ref++;
+		dout("%s %p wb %d -> %d (?)\n", __func__,
+		     &ci->netfs.inode, ci->i_wb_ref-1, ci->i_wb_ref);
+	}
+}
+
+/*
+ * Try to grab cap references.  Specify those refs we @want, and the
+ * minimal set we @need.  Also include the larger offset we are writing
+ * to (when applicable), and check against max_size here as well.
+ * Note that caller is responsible for ensuring max_size increases are
+ * requested from the MDS.
+ *
+ * Returns 0 if caps were not able to be acquired (yet), 1 if succeed,
+ * or a negative error code. There are 3 speical error codes:
+ *  -EAGAIN:  need to sleep but non-blocking is specified
+ *  -EFBIG:   ask caller to call check_max_size() and try again.
+ *  -EUCLEAN: ask caller to call ceph_renew_caps() and try again.
+ */
+enum {
+	/* first 8 bits are reserved for CEPH_FILE_MODE_FOO */
+	NON_BLOCKING	= (1 << 8),
+	CHECK_FILELOCK	= (1 << 9),
+};
+
+static int try_get_cap_refs(struct inode *inode, int need, int want,
+			    loff_t endoff, int flags, int *got)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;
+	int ret = 0;
+	int have, implemented;
+	bool snap_rwsem_locked = false;
+
+	dout("get_cap_refs %p need %s want %s\n", inode,
+	     ceph_cap_string(need), ceph_cap_string(want));
+
+again:
+	spin_lock(&ci->i_ceph_lock);
+
+	if ((flags & CHECK_FILELOCK) &&
+	    (ci->i_ceph_flags & CEPH_I_ERROR_FILELOCK)) {
+		dout("try_get_cap_refs %p error filelock\n", inode);
+		ret = -EIO;
+		goto out_unlock;
+	}
+
+	/* finish pending truncate */
+	while (ci->i_truncate_pending) {
+		spin_unlock(&ci->i_ceph_lock);
+		if (snap_rwsem_locked) {
+			up_read(&mdsc->snap_rwsem);
+			snap_rwsem_locked = false;
+		}
+		__ceph_do_pending_vmtruncate(inode);
+		spin_lock(&ci->i_ceph_lock);
+	}
+
+	have = __ceph_caps_issued(ci, &implemented);
+
+	if (have & need & CEPH_CAP_FILE_WR) {
+		if (endoff >= 0 && endoff > (loff_t)ci->i_max_size) {
+			dout("get_cap_refs %p endoff %llu > maxsize %llu\n",
+			     inode, endoff, ci->i_max_size);
+			if (endoff > ci->i_requested_max_size)
+				ret = ci->i_auth_cap ? -EFBIG : -EUCLEAN;
+			goto out_unlock;
+		}
+		/*
+		 * If a sync write is in progress, we must wait, so that we
+		 * can get a final snapshot value for size+mtime.
+		 */
+		if (__ceph_have_pending_cap_snap(ci)) {
+			dout("get_cap_refs %p cap_snap_pending\n", inode);
+			goto out_unlock;
+		}
+	}
+
+	if ((have & need) == need) {
+		/*
+		 * Look at (implemented & ~have & not) so that we keep waiting
+		 * on transition from wanted -> needed caps.  This is needed
+		 * for WRBUFFER|WR -> WR to avoid a new WR sync write from
+		 * going before a prior buffered writeback happens.
+		 *
+		 * For RDCACHE|RD -> RD, there is not need to wait and we can
+		 * just exclude the revoking caps and force to sync read.
+		 */
+		int not = want & ~(have & need);
+		int revoking = implemented & ~have;
+		int exclude = revoking & not;
+		dout("get_cap_refs %p have %s but not %s (revoking %s)\n",
+		     inode, ceph_cap_string(have), ceph_cap_string(not),
+		     ceph_cap_string(revoking));
+		if (!exclude || !(exclude & CEPH_CAP_FILE_BUFFER)) {
+			if (!snap_rwsem_locked &&
+			    !ci->i_head_snapc &&
+			    (need & CEPH_CAP_FILE_WR)) {
+				if (!down_read_trylock(&mdsc->snap_rwsem)) {
+					/*
+					 * we can not call down_read() when
+					 * task isn't in TASK_RUNNING state
+					 */
+					if (flags & NON_BLOCKING) {
+						ret = -EAGAIN;
+						goto out_unlock;
+					}
+
+					spin_unlock(&ci->i_ceph_lock);
+					down_read(&mdsc->snap_rwsem);
+					snap_rwsem_locked = true;
+					goto again;
+				}
+				snap_rwsem_locked = true;
+			}
+			if ((have & want) == want)
+				*got = need | (want & ~exclude);
+			else
+				*got = need;
+			ceph_take_cap_refs(ci, *got, true);
+			ret = 1;
+		}
+	} else {
+		int session_readonly = false;
+		int mds_wanted;
+		if (ci->i_auth_cap &&
+		    (need & (CEPH_CAP_FILE_WR | CEPH_CAP_FILE_EXCL))) {
+			struct ceph_mds_session *s = ci->i_auth_cap->session;
+			spin_lock(&s->s_cap_lock);
+			session_readonly = s->s_readonly;
+			spin_unlock(&s->s_cap_lock);
+		}
+		if (session_readonly) {
+			dout("get_cap_refs %p need %s but mds%d readonly\n",
+			     inode, ceph_cap_string(need), ci->i_auth_cap->mds);
+			ret = -EROFS;
+			goto out_unlock;
+		}
+
+		if (ceph_inode_is_shutdown(inode)) {
+			dout("get_cap_refs %p inode is shutdown\n", inode);
+			ret = -ESTALE;
+			goto out_unlock;
+		}
+		mds_wanted = __ceph_caps_mds_wanted(ci, false);
+		if (need & ~mds_wanted) {
+			dout("get_cap_refs %p need %s > mds_wanted %s\n",
+			     inode, ceph_cap_string(need),
+			     ceph_cap_string(mds_wanted));
+			ret = -EUCLEAN;
+			goto out_unlock;
+		}
+
+		dout("get_cap_refs %p have %s need %s\n", inode,
+		     ceph_cap_string(have), ceph_cap_string(need));
+	}
+out_unlock:
+
+	__ceph_touch_fmode(ci, mdsc, flags);
+
+	spin_unlock(&ci->i_ceph_lock);
+	if (snap_rwsem_locked)
+		up_read(&mdsc->snap_rwsem);
+
+	if (!ret)
+		ceph_update_cap_mis(&mdsc->metric);
+	else if (ret == 1)
+		ceph_update_cap_hit(&mdsc->metric);
+
+	dout("get_cap_refs %p ret %d got %s\n", inode,
+	     ret, ceph_cap_string(*got));
+	return ret;
+}
+
+/*
+ * Check the offset we are writing up to against our current
+ * max_size.  If necessary, tell the MDS we want to write to
+ * a larger offset.
+ */
+static void check_max_size(struct inode *inode, loff_t endoff)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	int check = 0;
+
+	/* do we need to explicitly request a larger max_size? */
+	spin_lock(&ci->i_ceph_lock);
+	if (endoff >= ci->i_max_size && endoff > ci->i_wanted_max_size) {
+		dout("write %p at large endoff %llu, req max_size\n",
+		     inode, endoff);
+		ci->i_wanted_max_size = endoff;
+	}
+	/* duplicate ceph_check_caps()'s logic */
+	if (ci->i_auth_cap &&
+	    (ci->i_auth_cap->issued & CEPH_CAP_FILE_WR) &&
+	    ci->i_wanted_max_size > ci->i_max_size &&
+	    ci->i_wanted_max_size > ci->i_requested_max_size)
+		check = 1;
+	spin_unlock(&ci->i_ceph_lock);
+	if (check)
+		ceph_check_caps(ci, CHECK_CAPS_AUTHONLY, NULL);
+}
+
+static inline int get_used_fmode(int caps)
+{
+	int fmode = 0;
+	if (caps & CEPH_CAP_FILE_RD)
+		fmode |= CEPH_FILE_MODE_RD;
+	if (caps & CEPH_CAP_FILE_WR)
+		fmode |= CEPH_FILE_MODE_WR;
+	return fmode;
+}
+
+int ceph_try_get_caps(struct inode *inode, int need, int want,
+		      bool nonblock, int *got)
+{
+	int ret, flags;
+
+	BUG_ON(need & ~CEPH_CAP_FILE_RD);
+	BUG_ON(want & ~(CEPH_CAP_FILE_CACHE | CEPH_CAP_FILE_LAZYIO |
+			CEPH_CAP_FILE_SHARED | CEPH_CAP_FILE_EXCL |
+			CEPH_CAP_ANY_DIR_OPS));
+	if (need) {
+		ret = ceph_pool_perm_check(inode, need);
+		if (ret < 0)
+			return ret;
+	}
+
+	flags = get_used_fmode(need | want);
+	if (nonblock)
+		flags |= NON_BLOCKING;
+
+	ret = try_get_cap_refs(inode, need, want, 0, flags, got);
+	/* three special error codes */
+	if (ret == -EAGAIN || ret == -EFBIG || ret == -EUCLEAN)
+		ret = 0;
+	return ret;
+}
+
+/*
+ * Wait for caps, and take cap references.  If we can't get a WR cap
+ * due to a small max_size, make sure we check_max_size (and possibly
+ * ask the mds) so we don't get hung up indefinitely.
+ */
+int ceph_get_caps(struct file *filp, int need, int want, loff_t endoff, int *got)
+{
+	struct ceph_file_info *fi = filp->private_data;
+	struct inode *inode = file_inode(filp);
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
+	int ret, _got, flags;
+
+	ret = ceph_pool_perm_check(inode, need);
+	if (ret < 0)
+		return ret;
+
+	if ((fi->fmode & CEPH_FILE_MODE_WR) &&
+	    fi->filp_gen != READ_ONCE(fsc->filp_gen))
+		return -EBADF;
+
+	flags = get_used_fmode(need | want);
+
+	while (true) {
+		flags &= CEPH_FILE_MODE_MASK;
+		if (vfs_inode_has_locks(inode))
+			flags |= CHECK_FILELOCK;
+		_got = 0;
+		ret = try_get_cap_refs(inode, need, want, endoff,
+				       flags, &_got);
+		WARN_ON_ONCE(ret == -EAGAIN);
+		if (!ret) {
+			struct ceph_mds_client *mdsc = fsc->mdsc;
+			struct cap_wait cw;
+			DEFINE_WAIT_FUNC(wait, woken_wake_function);
+
+			cw.ino = ceph_ino(inode);
+			cw.tgid = current->tgid;
+			cw.need = need;
+			cw.want = want;
+
+			spin_lock(&mdsc->caps_list_lock);
+			list_add(&cw.list, &mdsc->cap_wait_list);
+			spin_unlock(&mdsc->caps_list_lock);
+
+			/* make sure used fmode not timeout */
+			ceph_get_fmode(ci, flags, FMODE_WAIT_BIAS);
+			add_wait_queue(&ci->i_cap_wq, &wait);
+
+			flags |= NON_BLOCKING;
+			while (!(ret = try_get_cap_refs(inode, need, want,
+							endoff, flags, &_got))) {
+				if (signal_pending(current)) {
+					ret = -ERESTARTSYS;
+					break;
+				}
+				wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
+			}
+
+			remove_wait_queue(&ci->i_cap_wq, &wait);
+			ceph_put_fmode(ci, flags, FMODE_WAIT_BIAS);
+
+			spin_lock(&mdsc->caps_list_lock);
+			list_del(&cw.list);
+			spin_unlock(&mdsc->caps_list_lock);
+
+			if (ret == -EAGAIN)
+				continue;
+		}
+
+		if ((fi->fmode & CEPH_FILE_MODE_WR) &&
+		    fi->filp_gen != READ_ONCE(fsc->filp_gen)) {
+			if (ret >= 0 && _got)
+				ceph_put_cap_refs(ci, _got);
+			return -EBADF;
+		}
+
+		if (ret < 0) {
+			if (ret == -EFBIG || ret == -EUCLEAN) {
+				int ret2 = ceph_wait_on_async_create(inode);
+				if (ret2 < 0)
+					return ret2;
+			}
+			if (ret == -EFBIG) {
+				check_max_size(inode, endoff);
+				continue;
+			}
+			if (ret == -EUCLEAN) {
+				/* session was killed, try renew caps */
+				ret = ceph_renew_caps(inode, flags);
+				if (ret == 0)
+					continue;
+			}
+			return ret;
+		}
+
+		if (S_ISREG(ci->netfs.inode.i_mode) &&
+		    ceph_has_inline_data(ci) &&
+		    (_got & (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO)) &&
+		    i_size_read(inode) > 0) {
+			struct page *page =
+				find_get_page(inode->i_mapping, 0);
+			if (page) {
+				bool uptodate = PageUptodate(page);
+
+				put_page(page);
+				if (uptodate)
+					break;
+			}
+			/*
+			 * drop cap refs first because getattr while
+			 * holding * caps refs can cause deadlock.
+			 */
+			ceph_put_cap_refs(ci, _got);
+			_got = 0;
+
+			/*
+			 * getattr request will bring inline data into
+			 * page cache
+			 */
+			ret = __ceph_do_getattr(inode, NULL,
+						CEPH_STAT_CAP_INLINE_DATA,
+						true);
+			if (ret < 0)
+				return ret;
+			continue;
+		}
+		break;
+	}
+	*got = _got;
+	return 0;
+}
+
+/*
+ * Take cap refs.  Caller must already know we hold at least one ref
+ * on the caps in question or we don't know this is safe.
+ */
+void ceph_get_cap_refs(struct ceph_inode_info *ci, int caps)
+{
+	spin_lock(&ci->i_ceph_lock);
+	ceph_take_cap_refs(ci, caps, false);
+	spin_unlock(&ci->i_ceph_lock);
+}
+
+
+/*
+ * drop cap_snap that is not associated with any snapshot.
+ * we don't need to send FLUSHSNAP message for it.
+ */
+static int ceph_try_drop_cap_snap(struct ceph_inode_info *ci,
+				  struct ceph_cap_snap *capsnap)
+{
+	if (!capsnap->need_flush &&
+	    !capsnap->writing && !capsnap->dirty_pages) {
+		dout("dropping cap_snap %p follows %llu\n",
+		     capsnap, capsnap->follows);
+		BUG_ON(capsnap->cap_flush.tid > 0);
+		ceph_put_snap_context(capsnap->context);
+		if (!list_is_last(&capsnap->ci_item, &ci->i_cap_snaps))
+			ci->i_ceph_flags |= CEPH_I_FLUSH_SNAPS;
+
+		list_del(&capsnap->ci_item);
+		ceph_put_cap_snap(capsnap);
+		return 1;
+	}
+	return 0;
+}
+
+enum put_cap_refs_mode {
+	PUT_CAP_REFS_SYNC = 0,
+	PUT_CAP_REFS_NO_CHECK,
+	PUT_CAP_REFS_ASYNC,
+};
+
+/*
+ * Release cap refs.
+ *
+ * If we released the last ref on any given cap, call ceph_check_caps
+ * to release (or schedule a release).
+ *
+ * If we are releasing a WR cap (from a sync write), finalize any affected
+ * cap_snap, and wake up any waiters.
+ */
+static void __ceph_put_cap_refs(struct ceph_inode_info *ci, int had,
+				enum put_cap_refs_mode mode)
+{
+	struct inode *inode = &ci->netfs.inode;
+	int last = 0, put = 0, flushsnaps = 0, wake = 0;
+	bool check_flushsnaps = false;
+
+	spin_lock(&ci->i_ceph_lock);
+	if (had & CEPH_CAP_PIN)
+		--ci->i_pin_ref;
+	if (had & CEPH_CAP_FILE_RD)
+		if (--ci->i_rd_ref == 0)
+			last++;
+	if (had & CEPH_CAP_FILE_CACHE)
+		if (--ci->i_rdcache_ref == 0)
+			last++;
+	if (had & CEPH_CAP_FILE_EXCL)
+		if (--ci->i_fx_ref == 0)
+			last++;
+	if (had & CEPH_CAP_FILE_BUFFER) {
+		if (--ci->i_wb_ref == 0) {
+			last++;
+			/* put the ref held by ceph_take_cap_refs() */
+			put++;
+			check_flushsnaps = true;
+		}
+		dout("put_cap_refs %p wb %d -> %d (?)\n",
+		     inode, ci->i_wb_ref+1, ci->i_wb_ref);
+	}
+	if (had & CEPH_CAP_FILE_WR) {
+		if (--ci->i_wr_ref == 0) {
+			last++;
+			check_flushsnaps = true;
+			if (ci->i_wrbuffer_ref_head == 0 &&
+			    ci->i_dirty_caps == 0 &&
+			    ci->i_flushing_caps == 0) {
+				BUG_ON(!ci->i_head_snapc);
+				ceph_put_snap_context(ci->i_head_snapc);
+				ci->i_head_snapc = NULL;
+			}
+			/* see comment in __ceph_remove_cap() */
+			if (!__ceph_is_any_real_caps(ci) && ci->i_snap_realm)
+				ceph_change_snap_realm(inode, NULL);
+		}
+	}
+	if (check_flushsnaps && __ceph_have_pending_cap_snap(ci)) {
+		struct ceph_cap_snap *capsnap =
+			list_last_entry(&ci->i_cap_snaps,
+					struct ceph_cap_snap,
+					ci_item);
+
+		capsnap->writing = 0;
+		if (ceph_try_drop_cap_snap(ci, capsnap))
+			/* put the ref held by ceph_queue_cap_snap() */
+			put++;
+		else if (__ceph_finish_cap_snap(ci, capsnap))
+			flushsnaps = 1;
+		wake = 1;
+	}
+	spin_unlock(&ci->i_ceph_lock);
+
+	dout("put_cap_refs %p had %s%s%s\n", inode, ceph_cap_string(had),
+	     last ? " last" : "", put ? " put" : "");
+
+	switch (mode) {
+	case PUT_CAP_REFS_SYNC:
+		if (last)
+			ceph_check_caps(ci, 0, NULL);
+		else if (flushsnaps)
+			ceph_flush_snaps(ci, NULL);
+		break;
+	case PUT_CAP_REFS_ASYNC:
+		if (last)
+			ceph_queue_check_caps(inode);
+		else if (flushsnaps)
+			ceph_queue_flush_snaps(inode);
+		break;
+	default:
+		break;
+	}
+	if (wake)
+		wake_up_all(&ci->i_cap_wq);
+	while (put-- > 0)
+		iput(inode);
+}
+
+void ceph_put_cap_refs(struct ceph_inode_info *ci, int had)
+{
+	__ceph_put_cap_refs(ci, had, PUT_CAP_REFS_SYNC);
+}
+
+void ceph_put_cap_refs_async(struct ceph_inode_info *ci, int had)
+{
+	__ceph_put_cap_refs(ci, had, PUT_CAP_REFS_ASYNC);
+}
+
+void ceph_put_cap_refs_no_check_caps(struct ceph_inode_info *ci, int had)
+{
+	__ceph_put_cap_refs(ci, had, PUT_CAP_REFS_NO_CHECK);
+}
+
+/*
+ * Release @nr WRBUFFER refs on dirty pages for the given @snapc snap
+ * context.  Adjust per-snap dirty page accounting as appropriate.
+ * Once all dirty data for a cap_snap is flushed, flush snapped file
+ * metadata back to the MDS.  If we dropped the last ref, call
+ * ceph_check_caps.
+ */
+void ceph_put_wrbuffer_cap_refs(struct ceph_inode_info *ci, int nr,
+				struct ceph_snap_context *snapc)
+{
+	struct inode *inode = &ci->netfs.inode;
+	struct ceph_cap_snap *capsnap = NULL, *iter;
+	int put = 0;
+	bool last = false;
+	bool flush_snaps = false;
+	bool complete_capsnap = false;
+
+	spin_lock(&ci->i_ceph_lock);
+	ci->i_wrbuffer_ref -= nr;
+	if (ci->i_wrbuffer_ref == 0) {
+		last = true;
+		put++;
+	}
+
+	if (ci->i_head_snapc == snapc) {
+		ci->i_wrbuffer_ref_head -= nr;
+		if (ci->i_wrbuffer_ref_head == 0 &&
+		    ci->i_wr_ref == 0 &&
+		    ci->i_dirty_caps == 0 &&
+		    ci->i_flushing_caps == 0) {
+			BUG_ON(!ci->i_head_snapc);
+			ceph_put_snap_context(ci->i_head_snapc);
+			ci->i_head_snapc = NULL;
+		}
+		dout("put_wrbuffer_cap_refs on %p head %d/%d -> %d/%d %s\n",
+		     inode,
+		     ci->i_wrbuffer_ref+nr, ci->i_wrbuffer_ref_head+nr,
+		     ci->i_wrbuffer_ref, ci->i_wrbuffer_ref_head,
+		     last ? " LAST" : "");
+	} else {
+		list_for_each_entry(iter, &ci->i_cap_snaps, ci_item) {
+			if (iter->context == snapc) {
+				capsnap = iter;
+				break;
+			}
+		}
+
+		if (!capsnap) {
+			/*
+			 * The capsnap should already be removed when removing
+			 * auth cap in the case of a forced unmount.
+			 */
+			WARN_ON_ONCE(ci->i_auth_cap);
+			goto unlock;
+		}
+
+		capsnap->dirty_pages -= nr;
+		if (capsnap->dirty_pages == 0) {
+			complete_capsnap = true;
+			if (!capsnap->writing) {
+				if (ceph_try_drop_cap_snap(ci, capsnap)) {
+					put++;
+				} else {
+					ci->i_ceph_flags |= CEPH_I_FLUSH_SNAPS;
+					flush_snaps = true;
+				}
+			}
+		}
+		dout("put_wrbuffer_cap_refs on %p cap_snap %p "
+		     " snap %lld %d/%d -> %d/%d %s%s\n",
+		     inode, capsnap, capsnap->context->seq,
+		     ci->i_wrbuffer_ref+nr, capsnap->dirty_pages + nr,
+		     ci->i_wrbuffer_ref, capsnap->dirty_pages,
+		     last ? " (wrbuffer last)" : "",
+		     complete_capsnap ? " (complete capsnap)" : "");
+	}
+
+unlock:
+	spin_unlock(&ci->i_ceph_lock);
+
+	if (last) {
+		ceph_check_caps(ci, 0, NULL);
+	} else if (flush_snaps) {
+		ceph_flush_snaps(ci, NULL);
+	}
+	if (complete_capsnap)
+		wake_up_all(&ci->i_cap_wq);
+	while (put-- > 0) {
+		iput(inode);
+	}
+}
+
+/*
+ * Invalidate unlinked inode's aliases, so we can drop the inode ASAP.
+ */
+static void invalidate_aliases(struct inode *inode)
+{
+	struct dentry *dn, *prev = NULL;
+
+	dout("invalidate_aliases inode %p\n", inode);
+	d_prune_aliases(inode);
+	/*
+	 * For non-directory inode, d_find_alias() only returns
+	 * hashed dentry. After calling d_invalidate(), the
+	 * dentry becomes unhashed.
+	 *
+	 * For directory inode, d_find_alias() can return
+	 * unhashed dentry. But directory inode should have
+	 * one alias at most.
+	 */
+	while ((dn = d_find_alias(inode))) {
+		if (dn == prev) {
+			dput(dn);
+			break;
+		}
+		d_invalidate(dn);
+		if (prev)
+			dput(prev);
+		prev = dn;
+	}
+	if (prev)
+		dput(prev);
+}
+
+struct cap_extra_info {
+	struct ceph_string *pool_ns;
+	/* inline data */
+	u64 inline_version;
+	void *inline_data;
+	u32 inline_len;
+	/* dirstat */
+	bool dirstat_valid;
+	u64 nfiles;
+	u64 nsubdirs;
+	u64 change_attr;
+	/* currently issued */
+	int issued;
+	struct timespec64 btime;
+};
+
+/*
+ * Handle a cap GRANT message from the MDS.  (Note that a GRANT may
+ * actually be a revocation if it specifies a smaller cap set.)
+ *
+ * caller holds s_mutex and i_ceph_lock, we drop both.
+ */
+static void handle_cap_grant(struct inode *inode,
+			     struct ceph_mds_session *session,
+			     struct ceph_cap *cap,
+			     struct ceph_mds_caps *grant,
+			     struct ceph_buffer *xattr_buf,
+			     struct cap_extra_info *extra_info)
+	__releases(ci->i_ceph_lock)
+	__releases(session->s_mdsc->snap_rwsem)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	int seq = le32_to_cpu(grant->seq);
+	int newcaps = le32_to_cpu(grant->caps);
+	int used, wanted, dirty;
+	u64 size = le64_to_cpu(grant->size);
+	u64 max_size = le64_to_cpu(grant->max_size);
+	unsigned char check_caps = 0;
+	bool was_stale = cap->cap_gen < atomic_read(&session->s_cap_gen);
+	bool wake = false;
+	bool writeback = false;
+	bool queue_trunc = false;
+	bool queue_invalidate = false;
+	bool deleted_inode = false;
+	bool fill_inline = false;
+
+	dout("handle_cap_grant inode %p cap %p mds%d seq %d %s\n",
+	     inode, cap, session->s_mds, seq, ceph_cap_string(newcaps));
+	dout(" size %llu max_size %llu, i_size %llu\n", size, max_size,
+		i_size_read(inode));
+
+
+	/*
+	 * If CACHE is being revoked, and we have no dirty buffers,
+	 * try to invalidate (once).  (If there are dirty buffers, we
+	 * will invalidate _after_ writeback.)
+	 */
+	if (S_ISREG(inode->i_mode) && /* don't invalidate readdir cache */
+	    ((cap->issued & ~newcaps) & CEPH_CAP_FILE_CACHE) &&
+	    (newcaps & CEPH_CAP_FILE_LAZYIO) == 0 &&
+	    !(ci->i_wrbuffer_ref || ci->i_wb_ref)) {
+		if (try_nonblocking_invalidate(inode)) {
+			/* there were locked pages.. invalidate later
+			   in a separate thread. */
+			if (ci->i_rdcache_revoking != ci->i_rdcache_gen) {
+				queue_invalidate = true;
+				ci->i_rdcache_revoking = ci->i_rdcache_gen;
+			}
+		}
+	}
+
+	if (was_stale)
+		cap->issued = cap->implemented = CEPH_CAP_PIN;
+
+	/*
+	 * auth mds of the inode changed. we received the cap export message,
+	 * but still haven't received the cap import message. handle_cap_export
+	 * updated the new auth MDS' cap.
+	 *
+	 * "ceph_seq_cmp(seq, cap->seq) <= 0" means we are processing a message
+	 * that was sent before the cap import message. So don't remove caps.
+	 */
+	if (ceph_seq_cmp(seq, cap->seq) <= 0) {
+		WARN_ON(cap != ci->i_auth_cap);
+		WARN_ON(cap->cap_id != le64_to_cpu(grant->cap_id));
+		seq = cap->seq;
+		newcaps |= cap->issued;
+	}
+
+	/* side effects now are allowed */
+	cap->cap_gen = atomic_read(&session->s_cap_gen);
+	cap->seq = seq;
+
+	__check_cap_issue(ci, cap, newcaps);
+
+	inode_set_max_iversion_raw(inode, extra_info->change_attr);
+
+	if ((newcaps & CEPH_CAP_AUTH_SHARED) &&
+	    (extra_info->issued & CEPH_CAP_AUTH_EXCL) == 0) {
+		umode_t mode = le32_to_cpu(grant->mode);
+
+		if (inode_wrong_type(inode, mode))
+			pr_warn_once("inode type changed! (ino %llx.%llx is 0%o, mds says 0%o)\n",
+				     ceph_vinop(inode), inode->i_mode, mode);
+		else
+			inode->i_mode = mode;
+		inode->i_uid = make_kuid(&init_user_ns, le32_to_cpu(grant->uid));
+		inode->i_gid = make_kgid(&init_user_ns, le32_to_cpu(grant->gid));
+		ci->i_btime = extra_info->btime;
+		dout("%p mode 0%o uid.gid %d.%d\n", inode, inode->i_mode,
+		     from_kuid(&init_user_ns, inode->i_uid),
+		     from_kgid(&init_user_ns, inode->i_gid));
+	}
+
+	if ((newcaps & CEPH_CAP_LINK_SHARED) &&
+	    (extra_info->issued & CEPH_CAP_LINK_EXCL) == 0) {
+		set_nlink(inode, le32_to_cpu(grant->nlink));
+		if (inode->i_nlink == 0)
+			deleted_inode = true;
+	}
+
+	if ((extra_info->issued & CEPH_CAP_XATTR_EXCL) == 0 &&
+	    grant->xattr_len) {
+		int len = le32_to_cpu(grant->xattr_len);
+		u64 version = le64_to_cpu(grant->xattr_version);
+
+		if (version > ci->i_xattrs.version) {
+			dout(" got new xattrs v%llu on %p len %d\n",
+			     version, inode, len);
+			if (ci->i_xattrs.blob)
+				ceph_buffer_put(ci->i_xattrs.blob);
+			ci->i_xattrs.blob = ceph_buffer_get(xattr_buf);
+			ci->i_xattrs.version = version;
+			ceph_forget_all_cached_acls(inode);
+			ceph_security_invalidate_secctx(inode);
+		}
+	}
+
+	if (newcaps & CEPH_CAP_ANY_RD) {
+		struct timespec64 mtime, atime, ctime;
+		/* ctime/mtime/atime? */
+		ceph_decode_timespec64(&mtime, &grant->mtime);
+		ceph_decode_timespec64(&atime, &grant->atime);
+		ceph_decode_timespec64(&ctime, &grant->ctime);
+		ceph_fill_file_time(inode, extra_info->issued,
+				    le32_to_cpu(grant->time_warp_seq),
+				    &ctime, &mtime, &atime);
+	}
+
+	if ((newcaps & CEPH_CAP_FILE_SHARED) && extra_info->dirstat_valid) {
+		ci->i_files = extra_info->nfiles;
+		ci->i_subdirs = extra_info->nsubdirs;
+	}
+
+	if (newcaps & (CEPH_CAP_ANY_FILE_RD | CEPH_CAP_ANY_FILE_WR)) {
+		/* file layout may have changed */
+		s64 old_pool = ci->i_layout.pool_id;
+		struct ceph_string *old_ns;
+
+		ceph_file_layout_from_legacy(&ci->i_layout, &grant->layout);
+		old_ns = rcu_dereference_protected(ci->i_layout.pool_ns,
+					lockdep_is_held(&ci->i_ceph_lock));
+		rcu_assign_pointer(ci->i_layout.pool_ns, extra_info->pool_ns);
+
+		if (ci->i_layout.pool_id != old_pool ||
+		    extra_info->pool_ns != old_ns)
+			ci->i_ceph_flags &= ~CEPH_I_POOL_PERM;
+
+		extra_info->pool_ns = old_ns;
+
+		/* size/truncate_seq? */
+		queue_trunc = ceph_fill_file_size(inode, extra_info->issued,
+					le32_to_cpu(grant->truncate_seq),
+					le64_to_cpu(grant->truncate_size),
+					size);
+	}
+
+	if (ci->i_auth_cap == cap && (newcaps & CEPH_CAP_ANY_FILE_WR)) {
+		if (max_size != ci->i_max_size) {
+			dout("max_size %lld -> %llu\n",
+			     ci->i_max_size, max_size);
+			ci->i_max_size = max_size;
+			if (max_size >= ci->i_wanted_max_size) {
+				ci->i_wanted_max_size = 0;  /* reset */
+				ci->i_requested_max_size = 0;
+			}
+			wake = true;
+		}
+	}
+
+	/* check cap bits */
+	wanted = __ceph_caps_wanted(ci);
+	used = __ceph_caps_used(ci);
+	dirty = __ceph_caps_dirty(ci);
+	dout(" my wanted = %s, used = %s, dirty %s\n",
+	     ceph_cap_string(wanted),
+	     ceph_cap_string(used),
+	     ceph_cap_string(dirty));
+
+	if ((was_stale || le32_to_cpu(grant->op) == CEPH_CAP_OP_IMPORT) &&
+	    (wanted & ~(cap->mds_wanted | newcaps))) {
+		/*
+		 * If mds is importing cap, prior cap messages that update
+		 * 'wanted' may get dropped by mds (migrate seq mismatch).
+		 *
+		 * We don't send cap message to update 'wanted' if what we
+		 * want are already issued. If mds revokes caps, cap message
+		 * that releases caps also tells mds what we want. But if
+		 * caps got revoked by mds forcedly (session stale). We may
+		 * haven't told mds what we want.
+		 */
+		check_caps = 1;
+	}
+
+	/* revocation, grant, or no-op? */
+	if (cap->issued & ~newcaps) {
+		int revoking = cap->issued & ~newcaps;
+
+		dout("revocation: %s -> %s (revoking %s)\n",
+		     ceph_cap_string(cap->issued),
+		     ceph_cap_string(newcaps),
+		     ceph_cap_string(revoking));
+		if (S_ISREG(inode->i_mode) &&
+		    (revoking & used & CEPH_CAP_FILE_BUFFER))
+			writeback = true;  /* initiate writeback; will delay ack */
+		else if (queue_invalidate &&
+			 revoking == CEPH_CAP_FILE_CACHE &&
+			 (newcaps & CEPH_CAP_FILE_LAZYIO) == 0)
+			; /* do nothing yet, invalidation will be queued */
+		else if (cap == ci->i_auth_cap)
+			check_caps = 1; /* check auth cap only */
+		else
+			check_caps = 2; /* check all caps */
+		/* If there is new caps, try to wake up the waiters */
+		if (~cap->issued & newcaps)
+			wake = true;
+		cap->issued = newcaps;
+		cap->implemented |= newcaps;
+	} else if (cap->issued == newcaps) {
+		dout("caps unchanged: %s -> %s\n",
+		     ceph_cap_string(cap->issued), ceph_cap_string(newcaps));
+	} else {
+		dout("grant: %s -> %s\n", ceph_cap_string(cap->issued),
+		     ceph_cap_string(newcaps));
+		/* non-auth MDS is revoking the newly grant caps ? */
+		if (cap == ci->i_auth_cap &&
+		    __ceph_caps_revoking_other(ci, cap, newcaps))
+		    check_caps = 2;
+
+		cap->issued = newcaps;
+		cap->implemented |= newcaps; /* add bits only, to
+					      * avoid stepping on a
+					      * pending revocation */
+		wake = true;
+	}
+	BUG_ON(cap->issued & ~cap->implemented);
+
+	/* don't let check_caps skip sending a response to MDS for revoke msgs */
+	if (le32_to_cpu(grant->op) == CEPH_CAP_OP_REVOKE) {
+		cap->mds_wanted = 0;
+		if (cap == ci->i_auth_cap)
+			check_caps = 1; /* check auth cap only */
+		else
+			check_caps = 2; /* check all caps */
+	}
+
+	if (extra_info->inline_version > 0 &&
+	    extra_info->inline_version >= ci->i_inline_version) {
+		ci->i_inline_version = extra_info->inline_version;
+		if (ci->i_inline_version != CEPH_INLINE_NONE &&
+		    (newcaps & (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO)))
+			fill_inline = true;
+	}
+
+	if (le32_to_cpu(grant->op) == CEPH_CAP_OP_IMPORT) {
+		if (ci->i_auth_cap == cap) {
+			if (newcaps & ~extra_info->issued)
+				wake = true;
+
+			if (ci->i_requested_max_size > max_size ||
+			    !(le32_to_cpu(grant->wanted) & CEPH_CAP_ANY_FILE_WR)) {
+				/* re-request max_size if necessary */
+				ci->i_requested_max_size = 0;
+				wake = true;
+			}
+
+			ceph_kick_flushing_inode_caps(session, ci);
+		}
+		up_read(&session->s_mdsc->snap_rwsem);
+	}
+	spin_unlock(&ci->i_ceph_lock);
+
+	if (fill_inline)
+		ceph_fill_inline_data(inode, NULL, extra_info->inline_data,
+				      extra_info->inline_len);
+
+	if (queue_trunc)
+		ceph_queue_vmtruncate(inode);
+
+	if (writeback)
+		/*
+		 * queue inode for writeback: we can't actually call
+		 * filemap_write_and_wait, etc. from message handler
+		 * context.
+		 */
+		ceph_queue_writeback(inode);
+	if (queue_invalidate)
+		ceph_queue_invalidate(inode);
+	if (deleted_inode)
+		invalidate_aliases(inode);
+	if (wake)
+		wake_up_all(&ci->i_cap_wq);
+
+	mutex_unlock(&session->s_mutex);
+	if (check_caps == 1)
+		ceph_check_caps(ci, CHECK_CAPS_AUTHONLY | CHECK_CAPS_NOINVAL,
+				session);
+	else if (check_caps == 2)
+		ceph_check_caps(ci, CHECK_CAPS_NOINVAL, session);
+}
+
+/*
+ * Handle FLUSH_ACK from MDS, indicating that metadata we sent to the
+ * MDS has been safely committed.
+ */
+static void handle_cap_flush_ack(struct inode *inode, u64 flush_tid,
+				 struct ceph_mds_caps *m,
+				 struct ceph_mds_session *session,
+				 struct ceph_cap *cap)
+	__releases(ci->i_ceph_lock)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;
+	struct ceph_cap_flush *cf, *tmp_cf;
+	LIST_HEAD(to_remove);
+	unsigned seq = le32_to_cpu(m->seq);
+	int dirty = le32_to_cpu(m->dirty);
+	int cleaned = 0;
+	bool drop = false;
+	bool wake_ci = false;
+	bool wake_mdsc = false;
+
+	list_for_each_entry_safe(cf, tmp_cf, &ci->i_cap_flush_list, i_list) {
+		/* Is this the one that was flushed? */
+		if (cf->tid == flush_tid)
+			cleaned = cf->caps;
+
+		/* Is this a capsnap? */
+		if (cf->is_capsnap)
+			continue;
+
+		if (cf->tid <= flush_tid) {
+			/*
+			 * An earlier or current tid. The FLUSH_ACK should
+			 * represent a superset of this flush's caps.
+			 */
+			wake_ci |= __detach_cap_flush_from_ci(ci, cf);
+			list_add_tail(&cf->i_list, &to_remove);
+		} else {
+			/*
+			 * This is a later one. Any caps in it are still dirty
+			 * so don't count them as cleaned.
+			 */
+			cleaned &= ~cf->caps;
+			if (!cleaned)
+				break;
+		}
+	}
+
+	dout("handle_cap_flush_ack inode %p mds%d seq %d on %s cleaned %s,"
+	     " flushing %s -> %s\n",
+	     inode, session->s_mds, seq, ceph_cap_string(dirty),
+	     ceph_cap_string(cleaned), ceph_cap_string(ci->i_flushing_caps),
+	     ceph_cap_string(ci->i_flushing_caps & ~cleaned));
+
+	if (list_empty(&to_remove) && !cleaned)
+		goto out;
+
+	ci->i_flushing_caps &= ~cleaned;
+
+	spin_lock(&mdsc->cap_dirty_lock);
+
+	list_for_each_entry(cf, &to_remove, i_list)
+		wake_mdsc |= __detach_cap_flush_from_mdsc(mdsc, cf);
+
+	if (ci->i_flushing_caps == 0) {
+		if (list_empty(&ci->i_cap_flush_list)) {
+			list_del_init(&ci->i_flushing_item);
+			if (!list_empty(&session->s_cap_flushing)) {
+				dout(" mds%d still flushing cap on %p\n",
+				     session->s_mds,
+				     &list_first_entry(&session->s_cap_flushing,
+						struct ceph_inode_info,
+						i_flushing_item)->netfs.inode);
+			}
+		}
+		mdsc->num_cap_flushing--;
+		dout(" inode %p now !flushing\n", inode);
+
+		if (ci->i_dirty_caps == 0) {
+			dout(" inode %p now clean\n", inode);
+			BUG_ON(!list_empty(&ci->i_dirty_item));
+			drop = true;
+			if (ci->i_wr_ref == 0 &&
+			    ci->i_wrbuffer_ref_head == 0) {
+				BUG_ON(!ci->i_head_snapc);
+				ceph_put_snap_context(ci->i_head_snapc);
+				ci->i_head_snapc = NULL;
+			}
+		} else {
+			BUG_ON(list_empty(&ci->i_dirty_item));
+		}
+	}
+	spin_unlock(&mdsc->cap_dirty_lock);
+
+out:
+	spin_unlock(&ci->i_ceph_lock);
+
+	while (!list_empty(&to_remove)) {
+		cf = list_first_entry(&to_remove,
+				      struct ceph_cap_flush, i_list);
+		list_del_init(&cf->i_list);
+		if (!cf->is_capsnap)
+			ceph_free_cap_flush(cf);
+	}
+
+	if (wake_ci)
+		wake_up_all(&ci->i_cap_wq);
+	if (wake_mdsc)
+		wake_up_all(&mdsc->cap_flushing_wq);
+	if (drop)
+		iput(inode);
+}
+
+void __ceph_remove_capsnap(struct inode *inode, struct ceph_cap_snap *capsnap,
+			   bool *wake_ci, bool *wake_mdsc)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;
+	bool ret;
+
+	lockdep_assert_held(&ci->i_ceph_lock);
+
+	dout("removing capsnap %p, inode %p ci %p\n", capsnap, inode, ci);
+
+	list_del_init(&capsnap->ci_item);
+	ret = __detach_cap_flush_from_ci(ci, &capsnap->cap_flush);
+	if (wake_ci)
+		*wake_ci = ret;
+
+	spin_lock(&mdsc->cap_dirty_lock);
+	if (list_empty(&ci->i_cap_flush_list))
+		list_del_init(&ci->i_flushing_item);
+
+	ret = __detach_cap_flush_from_mdsc(mdsc, &capsnap->cap_flush);
+	if (wake_mdsc)
+		*wake_mdsc = ret;
+	spin_unlock(&mdsc->cap_dirty_lock);
+}
+
+void ceph_remove_capsnap(struct inode *inode, struct ceph_cap_snap *capsnap,
+			 bool *wake_ci, bool *wake_mdsc)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+
+	lockdep_assert_held(&ci->i_ceph_lock);
+
+	WARN_ON_ONCE(capsnap->dirty_pages || capsnap->writing);
+	__ceph_remove_capsnap(inode, capsnap, wake_ci, wake_mdsc);
+}
+
+/*
+ * Handle FLUSHSNAP_ACK.  MDS has flushed snap data to disk and we can
+ * throw away our cap_snap.
+ *
+ * Caller hold s_mutex.
+ */
+static void handle_cap_flushsnap_ack(struct inode *inode, u64 flush_tid,
+				     struct ceph_mds_caps *m,
+				     struct ceph_mds_session *session)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;
+	u64 follows = le64_to_cpu(m->snap_follows);
+	struct ceph_cap_snap *capsnap = NULL, *iter;
+	bool wake_ci = false;
+	bool wake_mdsc = false;
+
+	dout("handle_cap_flushsnap_ack inode %p ci %p mds%d follows %lld\n",
+	     inode, ci, session->s_mds, follows);
+
+	spin_lock(&ci->i_ceph_lock);
+	list_for_each_entry(iter, &ci->i_cap_snaps, ci_item) {
+		if (iter->follows == follows) {
+			if (iter->cap_flush.tid != flush_tid) {
+				dout(" cap_snap %p follows %lld tid %lld !="
+				     " %lld\n", iter, follows,
+				     flush_tid, iter->cap_flush.tid);
+				break;
+			}
+			capsnap = iter;
+			break;
+		} else {
+			dout(" skipping cap_snap %p follows %lld\n",
+			     iter, iter->follows);
+		}
+	}
+	if (capsnap)
+		ceph_remove_capsnap(inode, capsnap, &wake_ci, &wake_mdsc);
+	spin_unlock(&ci->i_ceph_lock);
+
+	if (capsnap) {
+		ceph_put_snap_context(capsnap->context);
+		ceph_put_cap_snap(capsnap);
+		if (wake_ci)
+			wake_up_all(&ci->i_cap_wq);
+		if (wake_mdsc)
+			wake_up_all(&mdsc->cap_flushing_wq);
+		iput(inode);
+	}
+}
+
+/*
+ * Handle TRUNC from MDS, indicating file truncation.
+ *
+ * caller hold s_mutex.
+ */
+static bool handle_cap_trunc(struct inode *inode,
+			     struct ceph_mds_caps *trunc,
+			     struct ceph_mds_session *session)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	int mds = session->s_mds;
+	int seq = le32_to_cpu(trunc->seq);
+	u32 truncate_seq = le32_to_cpu(trunc->truncate_seq);
+	u64 truncate_size = le64_to_cpu(trunc->truncate_size);
+	u64 size = le64_to_cpu(trunc->size);
+	int implemented = 0;
+	int dirty = __ceph_caps_dirty(ci);
+	int issued = __ceph_caps_issued(ceph_inode(inode), &implemented);
+	bool queue_trunc = false;
+
+	lockdep_assert_held(&ci->i_ceph_lock);
+
+	issued |= implemented | dirty;
+
+	dout("handle_cap_trunc inode %p mds%d seq %d to %lld seq %d\n",
+	     inode, mds, seq, truncate_size, truncate_seq);
+	queue_trunc = ceph_fill_file_size(inode, issued,
+					  truncate_seq, truncate_size, size);
+	return queue_trunc;
+}
+
+/*
+ * Handle EXPORT from MDS.  Cap is being migrated _from_ this mds to a
+ * different one.  If we are the most recent migration we've seen (as
+ * indicated by mseq), make note of the migrating cap bits for the
+ * duration (until we see the corresponding IMPORT).
+ *
+ * caller holds s_mutex
+ */
+static void handle_cap_export(struct inode *inode, struct ceph_mds_caps *ex,
+			      struct ceph_mds_cap_peer *ph,
+			      struct ceph_mds_session *session)
+{
+	struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;
+	struct ceph_mds_session *tsession = NULL;
+	struct ceph_cap *cap, *tcap, *new_cap = NULL;
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	u64 t_cap_id;
+	unsigned mseq = le32_to_cpu(ex->migrate_seq);
+	unsigned t_seq, t_mseq;
+	int target, issued;
+	int mds = session->s_mds;
+
+	if (ph) {
+		t_cap_id = le64_to_cpu(ph->cap_id);
+		t_seq = le32_to_cpu(ph->seq);
+		t_mseq = le32_to_cpu(ph->mseq);
+		target = le32_to_cpu(ph->mds);
+	} else {
+		t_cap_id = t_seq = t_mseq = 0;
+		target = -1;
+	}
+
+	dout("handle_cap_export inode %p ci %p mds%d mseq %d target %d\n",
+	     inode, ci, mds, mseq, target);
+retry:
+	down_read(&mdsc->snap_rwsem);
+	spin_lock(&ci->i_ceph_lock);
+	cap = __get_cap_for_mds(ci, mds);
+	if (!cap || cap->cap_id != le64_to_cpu(ex->cap_id))
+		goto out_unlock;
+
+	if (target < 0) {
+		ceph_remove_cap(cap, false);
+		goto out_unlock;
+	}
+
+	/*
+	 * now we know we haven't received the cap import message yet
+	 * because the exported cap still exist.
+	 */
+
+	issued = cap->issued;
+	if (issued != cap->implemented)
+		pr_err_ratelimited("handle_cap_export: issued != implemented: "
+				"ino (%llx.%llx) mds%d seq %d mseq %d "
+				"issued %s implemented %s\n",
+				ceph_vinop(inode), mds, cap->seq, cap->mseq,
+				ceph_cap_string(issued),
+				ceph_cap_string(cap->implemented));
+
+
+	tcap = __get_cap_for_mds(ci, target);
+	if (tcap) {
+		/* already have caps from the target */
+		if (tcap->cap_id == t_cap_id &&
+		    ceph_seq_cmp(tcap->seq, t_seq) < 0) {
+			dout(" updating import cap %p mds%d\n", tcap, target);
+			tcap->cap_id = t_cap_id;
+			tcap->seq = t_seq - 1;
+			tcap->issue_seq = t_seq - 1;
+			tcap->issued |= issued;
+			tcap->implemented |= issued;
+			if (cap == ci->i_auth_cap) {
+				ci->i_auth_cap = tcap;
+				change_auth_cap_ses(ci, tcap->session);
+			}
+		}
+		ceph_remove_cap(cap, false);
+		goto out_unlock;
+	} else if (tsession) {
+		/* add placeholder for the export tagert */
+		int flag = (cap == ci->i_auth_cap) ? CEPH_CAP_FLAG_AUTH : 0;
+		tcap = new_cap;
+		ceph_add_cap(inode, tsession, t_cap_id, issued, 0,
+			     t_seq - 1, t_mseq, (u64)-1, flag, &new_cap);
+
+		if (!list_empty(&ci->i_cap_flush_list) &&
+		    ci->i_auth_cap == tcap) {
+			spin_lock(&mdsc->cap_dirty_lock);
+			list_move_tail(&ci->i_flushing_item,
+				       &tcap->session->s_cap_flushing);
+			spin_unlock(&mdsc->cap_dirty_lock);
+		}
+
+		ceph_remove_cap(cap, false);
+		goto out_unlock;
+	}
+
+	spin_unlock(&ci->i_ceph_lock);
+	up_read(&mdsc->snap_rwsem);
+	mutex_unlock(&session->s_mutex);
+
+	/* open target session */
+	tsession = ceph_mdsc_open_export_target_session(mdsc, target);
+	if (!IS_ERR(tsession)) {
+		if (mds > target) {
+			mutex_lock(&session->s_mutex);
+			mutex_lock_nested(&tsession->s_mutex,
+					  SINGLE_DEPTH_NESTING);
+		} else {
+			mutex_lock(&tsession->s_mutex);
+			mutex_lock_nested(&session->s_mutex,
+					  SINGLE_DEPTH_NESTING);
+		}
+		new_cap = ceph_get_cap(mdsc, NULL);
+	} else {
+		WARN_ON(1);
+		tsession = NULL;
+		target = -1;
+		mutex_lock(&session->s_mutex);
+	}
+	goto retry;
+
+out_unlock:
+	spin_unlock(&ci->i_ceph_lock);
+	up_read(&mdsc->snap_rwsem);
+	mutex_unlock(&session->s_mutex);
+	if (tsession) {
+		mutex_unlock(&tsession->s_mutex);
+		ceph_put_mds_session(tsession);
+	}
+	if (new_cap)
+		ceph_put_cap(mdsc, new_cap);
+}
+
+/*
+ * Handle cap IMPORT.
+ *
+ * caller holds s_mutex. acquires i_ceph_lock
+ */
+static void handle_cap_import(struct ceph_mds_client *mdsc,
+			      struct inode *inode, struct ceph_mds_caps *im,
+			      struct ceph_mds_cap_peer *ph,
+			      struct ceph_mds_session *session,
+			      struct ceph_cap **target_cap, int *old_issued)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_cap *cap, *ocap, *new_cap = NULL;
+	int mds = session->s_mds;
+	int issued;
+	unsigned caps = le32_to_cpu(im->caps);
+	unsigned wanted = le32_to_cpu(im->wanted);
+	unsigned seq = le32_to_cpu(im->seq);
+	unsigned mseq = le32_to_cpu(im->migrate_seq);
+	u64 realmino = le64_to_cpu(im->realm);
+	u64 cap_id = le64_to_cpu(im->cap_id);
+	u64 p_cap_id;
+	int peer;
+
+	if (ph) {
+		p_cap_id = le64_to_cpu(ph->cap_id);
+		peer = le32_to_cpu(ph->mds);
+	} else {
+		p_cap_id = 0;
+		peer = -1;
+	}
+
+	dout("handle_cap_import inode %p ci %p mds%d mseq %d peer %d\n",
+	     inode, ci, mds, mseq, peer);
+retry:
+	cap = __get_cap_for_mds(ci, mds);
+	if (!cap) {
+		if (!new_cap) {
+			spin_unlock(&ci->i_ceph_lock);
+			new_cap = ceph_get_cap(mdsc, NULL);
+			spin_lock(&ci->i_ceph_lock);
+			goto retry;
+		}
+		cap = new_cap;
+	} else {
+		if (new_cap) {
+			ceph_put_cap(mdsc, new_cap);
+			new_cap = NULL;
+		}
+	}
+
+	__ceph_caps_issued(ci, &issued);
+	issued |= __ceph_caps_dirty(ci);
+
+	ceph_add_cap(inode, session, cap_id, caps, wanted, seq, mseq,
+		     realmino, CEPH_CAP_FLAG_AUTH, &new_cap);
+
+	ocap = peer >= 0 ? __get_cap_for_mds(ci, peer) : NULL;
+	if (ocap && ocap->cap_id == p_cap_id) {
+		dout(" remove export cap %p mds%d flags %d\n",
+		     ocap, peer, ph->flags);
+		if ((ph->flags & CEPH_CAP_FLAG_AUTH) &&
+		    (ocap->seq != le32_to_cpu(ph->seq) ||
+		     ocap->mseq != le32_to_cpu(ph->mseq))) {
+			pr_err_ratelimited("handle_cap_import: "
+					"mismatched seq/mseq: ino (%llx.%llx) "
+					"mds%d seq %d mseq %d importer mds%d "
+					"has peer seq %d mseq %d\n",
+					ceph_vinop(inode), peer, ocap->seq,
+					ocap->mseq, mds, le32_to_cpu(ph->seq),
+					le32_to_cpu(ph->mseq));
+		}
+		ceph_remove_cap(ocap, (ph->flags & CEPH_CAP_FLAG_RELEASE));
+	}
+
+	*old_issued = issued;
+	*target_cap = cap;
+}
+
+/*
+ * Handle a caps message from the MDS.
+ *
+ * Identify the appropriate session, inode, and call the right handler
+ * based on the cap op.
+ */
+void ceph_handle_caps(struct ceph_mds_session *session,
+		      struct ceph_msg *msg)
+{
+	struct ceph_mds_client *mdsc = session->s_mdsc;
+	struct inode *inode;
+	struct ceph_inode_info *ci;
+	struct ceph_cap *cap;
+	struct ceph_mds_caps *h;
+	struct ceph_mds_cap_peer *peer = NULL;
+	struct ceph_snap_realm *realm = NULL;
+	int op;
+	int msg_version = le16_to_cpu(msg->hdr.version);
+	u32 seq, mseq;
+	struct ceph_vino vino;
+	void *snaptrace;
+	size_t snaptrace_len;
+	void *p, *end;
+	struct cap_extra_info extra_info = {};
+	bool queue_trunc;
+	bool close_sessions = false;
+
+	dout("handle_caps from mds%d\n", session->s_mds);
+
+	if (!ceph_inc_mds_stopping_blocker(mdsc, session))
+		return;
+
+	/* decode */
+	end = msg->front.iov_base + msg->front.iov_len;
+	if (msg->front.iov_len < sizeof(*h))
+		goto bad;
+	h = msg->front.iov_base;
+	op = le32_to_cpu(h->op);
+	vino.ino = le64_to_cpu(h->ino);
+	vino.snap = CEPH_NOSNAP;
+	seq = le32_to_cpu(h->seq);
+	mseq = le32_to_cpu(h->migrate_seq);
+
+	snaptrace = h + 1;
+	snaptrace_len = le32_to_cpu(h->snap_trace_len);
+	p = snaptrace + snaptrace_len;
+
+	if (msg_version >= 2) {
+		u32 flock_len;
+		ceph_decode_32_safe(&p, end, flock_len, bad);
+		if (p + flock_len > end)
+			goto bad;
+		p += flock_len;
+	}
+
+	if (msg_version >= 3) {
+		if (op == CEPH_CAP_OP_IMPORT) {
+			if (p + sizeof(*peer) > end)
+				goto bad;
+			peer = p;
+			p += sizeof(*peer);
+		} else if (op == CEPH_CAP_OP_EXPORT) {
+			/* recorded in unused fields */
+			peer = (void *)&h->size;
+		}
+	}
+
+	if (msg_version >= 4) {
+		ceph_decode_64_safe(&p, end, extra_info.inline_version, bad);
+		ceph_decode_32_safe(&p, end, extra_info.inline_len, bad);
+		if (p + extra_info.inline_len > end)
+			goto bad;
+		extra_info.inline_data = p;
+		p += extra_info.inline_len;
+	}
+
+	if (msg_version >= 5) {
+		struct ceph_osd_client	*osdc = &mdsc->fsc->client->osdc;
+		u32			epoch_barrier;
+
+		ceph_decode_32_safe(&p, end, epoch_barrier, bad);
+		ceph_osdc_update_epoch_barrier(osdc, epoch_barrier);
+	}
+
+	if (msg_version >= 8) {
+		u32 pool_ns_len;
+
+		/* version >= 6 */
+		ceph_decode_skip_64(&p, end, bad);	// flush_tid
+		/* version >= 7 */
+		ceph_decode_skip_32(&p, end, bad);	// caller_uid
+		ceph_decode_skip_32(&p, end, bad);	// caller_gid
+		/* version >= 8 */
+		ceph_decode_32_safe(&p, end, pool_ns_len, bad);
+		if (pool_ns_len > 0) {
+			ceph_decode_need(&p, end, pool_ns_len, bad);
+			extra_info.pool_ns =
+				ceph_find_or_create_string(p, pool_ns_len);
+			p += pool_ns_len;
+		}
+	}
+
+	if (msg_version >= 9) {
+		struct ceph_timespec *btime;
+
+		if (p + sizeof(*btime) > end)
+			goto bad;
+		btime = p;
+		ceph_decode_timespec64(&extra_info.btime, btime);
+		p += sizeof(*btime);
+		ceph_decode_64_safe(&p, end, extra_info.change_attr, bad);
+	}
+
+	if (msg_version >= 11) {
+		/* version >= 10 */
+		ceph_decode_skip_32(&p, end, bad); // flags
+		/* version >= 11 */
+		extra_info.dirstat_valid = true;
+		ceph_decode_64_safe(&p, end, extra_info.nfiles, bad);
+		ceph_decode_64_safe(&p, end, extra_info.nsubdirs, bad);
+	}
+
+	/* lookup ino */
+	inode = ceph_find_inode(mdsc->fsc->sb, vino);
+	dout(" op %s ino %llx.%llx inode %p\n", ceph_cap_op_name(op), vino.ino,
+	     vino.snap, inode);
+
+	mutex_lock(&session->s_mutex);
+	dout(" mds%d seq %lld cap seq %u\n", session->s_mds, session->s_seq,
+	     (unsigned)seq);
+
+	if (!inode) {
+		dout(" i don't have ino %llx\n", vino.ino);
+
+		if (op == CEPH_CAP_OP_IMPORT) {
+			cap = ceph_get_cap(mdsc, NULL);
+			cap->cap_ino = vino.ino;
+			cap->queue_release = 1;
+			cap->cap_id = le64_to_cpu(h->cap_id);
+			cap->mseq = mseq;
+			cap->seq = seq;
+			cap->issue_seq = seq;
+			spin_lock(&session->s_cap_lock);
+			__ceph_queue_cap_release(session, cap);
+			spin_unlock(&session->s_cap_lock);
+		}
+		goto flush_cap_releases;
+	}
+	ci = ceph_inode(inode);
+
+	/* these will work even if we don't have a cap yet */
+	switch (op) {
+	case CEPH_CAP_OP_FLUSHSNAP_ACK:
+		handle_cap_flushsnap_ack(inode, le64_to_cpu(msg->hdr.tid),
+					 h, session);
+		goto done;
+
+	case CEPH_CAP_OP_EXPORT:
+		handle_cap_export(inode, h, peer, session);
+		goto done_unlocked;
+
+	case CEPH_CAP_OP_IMPORT:
+		realm = NULL;
+		if (snaptrace_len) {
+			down_write(&mdsc->snap_rwsem);
+			if (ceph_update_snap_trace(mdsc, snaptrace,
+						   snaptrace + snaptrace_len,
+						   false, &realm)) {
+				up_write(&mdsc->snap_rwsem);
+				close_sessions = true;
+				goto done;
+			}
+			downgrade_write(&mdsc->snap_rwsem);
+		} else {
+			down_read(&mdsc->snap_rwsem);
+		}
+		spin_lock(&ci->i_ceph_lock);
+		handle_cap_import(mdsc, inode, h, peer, session,
+				  &cap, &extra_info.issued);
+		handle_cap_grant(inode, session, cap,
+				 h, msg->middle, &extra_info);
+		if (realm)
+			ceph_put_snap_realm(mdsc, realm);
+		goto done_unlocked;
+	}
+
+	/* the rest require a cap */
+	spin_lock(&ci->i_ceph_lock);
+	cap = __get_cap_for_mds(ceph_inode(inode), session->s_mds);
+	if (!cap) {
+		dout(" no cap on %p ino %llx.%llx from mds%d\n",
+		     inode, ceph_ino(inode), ceph_snap(inode),
+		     session->s_mds);
+		spin_unlock(&ci->i_ceph_lock);
+		goto flush_cap_releases;
+	}
+
+	/* note that each of these drops i_ceph_lock for us */
+	switch (op) {
+	case CEPH_CAP_OP_REVOKE:
+	case CEPH_CAP_OP_GRANT:
+		__ceph_caps_issued(ci, &extra_info.issued);
+		extra_info.issued |= __ceph_caps_dirty(ci);
+		handle_cap_grant(inode, session, cap,
+				 h, msg->middle, &extra_info);
+		goto done_unlocked;
+
+	case CEPH_CAP_OP_FLUSH_ACK:
+		handle_cap_flush_ack(inode, le64_to_cpu(msg->hdr.tid),
+				     h, session, cap);
+		break;
+
+	case CEPH_CAP_OP_TRUNC:
+		queue_trunc = handle_cap_trunc(inode, h, session);
+		spin_unlock(&ci->i_ceph_lock);
+		if (queue_trunc)
+			ceph_queue_vmtruncate(inode);
+		break;
+
+	default:
+		spin_unlock(&ci->i_ceph_lock);
+		pr_err("ceph_handle_caps: unknown cap op %d %s\n", op,
+		       ceph_cap_op_name(op));
+	}
+
+done:
+	mutex_unlock(&session->s_mutex);
+done_unlocked:
+	iput(inode);
+out:
+	ceph_dec_mds_stopping_blocker(mdsc);
+
+	ceph_put_string(extra_info.pool_ns);
+
+	/* Defer closing the sessions after s_mutex lock being released */
+	if (close_sessions)
+		ceph_mdsc_close_sessions(mdsc);
+
+	return;
+
+flush_cap_releases:
+	/*
+	 * send any cap release message to try to move things
+	 * along for the mds (who clearly thinks we still have this
+	 * cap).
+	 */
+	ceph_flush_cap_releases(mdsc, session);
+	goto done;
+
+bad:
+	pr_err("ceph_handle_caps: corrupt message\n");
+	ceph_msg_dump(msg);
+	goto out;
+}
+
+/*
+ * Delayed work handler to process end of delayed cap release LRU list.
+ *
+ * If new caps are added to the list while processing it, these won't get
+ * processed in this run.  In this case, the ci->i_hold_caps_max will be
+ * returned so that the work can be scheduled accordingly.
+ */
+unsigned long ceph_check_delayed_caps(struct ceph_mds_client *mdsc)
+{
+	struct inode *inode;
+	struct ceph_inode_info *ci;
+	struct ceph_mount_options *opt = mdsc->fsc->mount_options;
+	unsigned long delay_max = opt->caps_wanted_delay_max * HZ;
+	unsigned long loop_start = jiffies;
+	unsigned long delay = 0;
+
+	dout("check_delayed_caps\n");
+	spin_lock(&mdsc->cap_delay_lock);
+	while (!list_empty(&mdsc->cap_delay_list)) {
+		ci = list_first_entry(&mdsc->cap_delay_list,
+				      struct ceph_inode_info,
+				      i_cap_delay_list);
+		if (time_before(loop_start, ci->i_hold_caps_max - delay_max)) {
+			dout("%s caps added recently.  Exiting loop", __func__);
+			delay = ci->i_hold_caps_max;
+			break;
+		}
+		if ((ci->i_ceph_flags & CEPH_I_FLUSH) == 0 &&
+		    time_before(jiffies, ci->i_hold_caps_max))
+			break;
+		list_del_init(&ci->i_cap_delay_list);
+
+		inode = igrab(&ci->netfs.inode);
+		if (inode) {
+			spin_unlock(&mdsc->cap_delay_lock);
+			dout("check_delayed_caps on %p\n", inode);
+			ceph_check_caps(ci, 0, NULL);
+			iput(inode);
+			spin_lock(&mdsc->cap_delay_lock);
+		}
+	}
+	spin_unlock(&mdsc->cap_delay_lock);
+
+	return delay;
+}
+
+/*
+ * Flush all dirty caps to the mds
+ */
+static void flush_dirty_session_caps(struct ceph_mds_session *s)
+{
+	struct ceph_mds_client *mdsc = s->s_mdsc;
+	struct ceph_inode_info *ci;
+	struct inode *inode;
+
+	dout("flush_dirty_caps\n");
+	spin_lock(&mdsc->cap_dirty_lock);
+	while (!list_empty(&s->s_cap_dirty)) {
+		ci = list_first_entry(&s->s_cap_dirty, struct ceph_inode_info,
+				      i_dirty_item);
+		inode = &ci->netfs.inode;
+		ihold(inode);
+		dout("flush_dirty_caps %llx.%llx\n", ceph_vinop(inode));
+		spin_unlock(&mdsc->cap_dirty_lock);
+		ceph_wait_on_async_create(inode);
+		ceph_check_caps(ci, CHECK_CAPS_FLUSH, NULL);
+		iput(inode);
+		spin_lock(&mdsc->cap_dirty_lock);
+	}
+	spin_unlock(&mdsc->cap_dirty_lock);
+	dout("flush_dirty_caps done\n");
+}
+
+void ceph_flush_dirty_caps(struct ceph_mds_client *mdsc)
+{
+	ceph_mdsc_iterate_sessions(mdsc, flush_dirty_session_caps, true);
+}
+
+void __ceph_touch_fmode(struct ceph_inode_info *ci,
+			struct ceph_mds_client *mdsc, int fmode)
+{
+	unsigned long now = jiffies;
+	if (fmode & CEPH_FILE_MODE_RD)
+		ci->i_last_rd = now;
+	if (fmode & CEPH_FILE_MODE_WR)
+		ci->i_last_wr = now;
+	/* queue periodic check */
+	if (fmode &&
+	    __ceph_is_any_real_caps(ci) &&
+	    list_empty(&ci->i_cap_delay_list))
+		__cap_delay_requeue(mdsc, ci);
+}
+
+void ceph_get_fmode(struct ceph_inode_info *ci, int fmode, int count)
+{
+	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(ci->netfs.inode.i_sb);
+	int bits = (fmode << 1) | 1;
+	bool already_opened = false;
+	int i;
+
+	if (count == 1)
+		atomic64_inc(&mdsc->metric.opened_files);
+
+	spin_lock(&ci->i_ceph_lock);
+	for (i = 0; i < CEPH_FILE_MODE_BITS; i++) {
+		/*
+		 * If any of the mode ref is larger than 0,
+		 * that means it has been already opened by
+		 * others. Just skip checking the PIN ref.
+		 */
+		if (i && ci->i_nr_by_mode[i])
+			already_opened = true;
+
+		if (bits & (1 << i))
+			ci->i_nr_by_mode[i] += count;
+	}
+
+	if (!already_opened)
+		percpu_counter_inc(&mdsc->metric.opened_inodes);
+	spin_unlock(&ci->i_ceph_lock);
+}
+
+/*
+ * Drop open file reference.  If we were the last open file,
+ * we may need to release capabilities to the MDS (or schedule
+ * their delayed release).
+ */
+void ceph_put_fmode(struct ceph_inode_info *ci, int fmode, int count)
+{
+	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(ci->netfs.inode.i_sb);
+	int bits = (fmode << 1) | 1;
+	bool is_closed = true;
+	int i;
+
+	if (count == 1)
+		atomic64_dec(&mdsc->metric.opened_files);
+
+	spin_lock(&ci->i_ceph_lock);
+	for (i = 0; i < CEPH_FILE_MODE_BITS; i++) {
+		if (bits & (1 << i)) {
+			BUG_ON(ci->i_nr_by_mode[i] < count);
+			ci->i_nr_by_mode[i] -= count;
+		}
+
+		/*
+		 * If any of the mode ref is not 0 after
+		 * decreased, that means it is still opened
+		 * by others. Just skip checking the PIN ref.
+		 */
+		if (i && ci->i_nr_by_mode[i])
+			is_closed = false;
+	}
+
+	if (is_closed)
+		percpu_counter_dec(&mdsc->metric.opened_inodes);
+	spin_unlock(&ci->i_ceph_lock);
+}
+
+/*
+ * For a soon-to-be unlinked file, drop the LINK caps. If it
+ * looks like the link count will hit 0, drop any other caps (other
+ * than PIN) we don't specifically want (due to the file still being
+ * open).
+ */
+int ceph_drop_caps_for_unlink(struct inode *inode)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	int drop = CEPH_CAP_LINK_SHARED | CEPH_CAP_LINK_EXCL;
+
+	spin_lock(&ci->i_ceph_lock);
+	if (inode->i_nlink == 1) {
+		drop |= ~(__ceph_caps_wanted(ci) | CEPH_CAP_PIN);
+
+		if (__ceph_caps_dirty(ci)) {
+			struct ceph_mds_client *mdsc =
+				ceph_inode_to_client(inode)->mdsc;
+			__cap_delay_requeue_front(mdsc, ci);
+		}
+	}
+	spin_unlock(&ci->i_ceph_lock);
+	return drop;
+}
+
+/*
+ * Helpers for embedding cap and dentry lease releases into mds
+ * requests.
+ *
+ * @force is used by dentry_release (below) to force inclusion of a
+ * record for the directory inode, even when there aren't any caps to
+ * drop.
+ */
+int ceph_encode_inode_release(void **p, struct inode *inode,
+			      int mds, int drop, int unless, int force)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_cap *cap;
+	struct ceph_mds_request_release *rel = *p;
+	int used, dirty;
+	int ret = 0;
+
+	spin_lock(&ci->i_ceph_lock);
+	used = __ceph_caps_used(ci);
+	dirty = __ceph_caps_dirty(ci);
+
+	dout("encode_inode_release %p mds%d used|dirty %s drop %s unless %s\n",
+	     inode, mds, ceph_cap_string(used|dirty), ceph_cap_string(drop),
+	     ceph_cap_string(unless));
+
+	/* only drop unused, clean caps */
+	drop &= ~(used | dirty);
+
+	cap = __get_cap_for_mds(ci, mds);
+	if (cap && __cap_is_valid(cap)) {
+		unless &= cap->issued;
+		if (unless) {
+			if (unless & CEPH_CAP_AUTH_EXCL)
+				drop &= ~CEPH_CAP_AUTH_SHARED;
+			if (unless & CEPH_CAP_LINK_EXCL)
+				drop &= ~CEPH_CAP_LINK_SHARED;
+			if (unless & CEPH_CAP_XATTR_EXCL)
+				drop &= ~CEPH_CAP_XATTR_SHARED;
+			if (unless & CEPH_CAP_FILE_EXCL)
+				drop &= ~CEPH_CAP_FILE_SHARED;
+		}
+
+		if (force || (cap->issued & drop)) {
+			if (cap->issued & drop) {
+				int wanted = __ceph_caps_wanted(ci);
+				dout("encode_inode_release %p cap %p "
+				     "%s -> %s, wanted %s -> %s\n", inode, cap,
+				     ceph_cap_string(cap->issued),
+				     ceph_cap_string(cap->issued & ~drop),
+				     ceph_cap_string(cap->mds_wanted),
+				     ceph_cap_string(wanted));
+
+				cap->issued &= ~drop;
+				cap->implemented &= ~drop;
+				cap->mds_wanted = wanted;
+				if (cap == ci->i_auth_cap &&
+				    !(wanted & CEPH_CAP_ANY_FILE_WR))
+					ci->i_requested_max_size = 0;
+			} else {
+				dout("encode_inode_release %p cap %p %s"
+				     " (force)\n", inode, cap,
+				     ceph_cap_string(cap->issued));
+			}
+
+			rel->ino = cpu_to_le64(ceph_ino(inode));
+			rel->cap_id = cpu_to_le64(cap->cap_id);
+			rel->seq = cpu_to_le32(cap->seq);
+			rel->issue_seq = cpu_to_le32(cap->issue_seq);
+			rel->mseq = cpu_to_le32(cap->mseq);
+			rel->caps = cpu_to_le32(cap->implemented);
+			rel->wanted = cpu_to_le32(cap->mds_wanted);
+			rel->dname_len = 0;
+			rel->dname_seq = 0;
+			*p += sizeof(*rel);
+			ret = 1;
+		} else {
+			dout("encode_inode_release %p cap %p %s (noop)\n",
+			     inode, cap, ceph_cap_string(cap->issued));
+		}
+	}
+	spin_unlock(&ci->i_ceph_lock);
+	return ret;
+}
+
+int ceph_encode_dentry_release(void **p, struct dentry *dentry,
+			       struct inode *dir,
+			       int mds, int drop, int unless)
+{
+	struct dentry *parent = NULL;
+	struct ceph_mds_request_release *rel = *p;
+	struct ceph_dentry_info *di = ceph_dentry(dentry);
+	int force = 0;
+	int ret;
+
+	/*
+	 * force an record for the directory caps if we have a dentry lease.
+	 * this is racy (can't take i_ceph_lock and d_lock together), but it
+	 * doesn't have to be perfect; the mds will revoke anything we don't
+	 * release.
+	 */
+	spin_lock(&dentry->d_lock);
+	if (di->lease_session && di->lease_session->s_mds == mds)
+		force = 1;
+	if (!dir) {
+		parent = dget(dentry->d_parent);
+		dir = d_inode(parent);
+	}
+	spin_unlock(&dentry->d_lock);
+
+	ret = ceph_encode_inode_release(p, dir, mds, drop, unless, force);
+	dput(parent);
+
+	spin_lock(&dentry->d_lock);
+	if (ret && di->lease_session && di->lease_session->s_mds == mds) {
+		dout("encode_dentry_release %p mds%d seq %d\n",
+		     dentry, mds, (int)di->lease_seq);
+		rel->dname_len = cpu_to_le32(dentry->d_name.len);
+		memcpy(*p, dentry->d_name.name, dentry->d_name.len);
+		*p += dentry->d_name.len;
+		rel->dname_seq = cpu_to_le32(di->lease_seq);
+		__ceph_mdsc_drop_dentry_lease(dentry);
+	}
+	spin_unlock(&dentry->d_lock);
+	return ret;
+}
+
+static int remove_capsnaps(struct ceph_mds_client *mdsc, struct inode *inode)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_cap_snap *capsnap;
+	int capsnap_release = 0;
+
+	lockdep_assert_held(&ci->i_ceph_lock);
+
+	dout("removing capsnaps, ci is %p, inode is %p\n", ci, inode);
+
+	while (!list_empty(&ci->i_cap_snaps)) {
+		capsnap = list_first_entry(&ci->i_cap_snaps,
+					   struct ceph_cap_snap, ci_item);
+		__ceph_remove_capsnap(inode, capsnap, NULL, NULL);
+		ceph_put_snap_context(capsnap->context);
+		ceph_put_cap_snap(capsnap);
+		capsnap_release++;
+	}
+	wake_up_all(&ci->i_cap_wq);
+	wake_up_all(&mdsc->cap_flushing_wq);
+	return capsnap_release;
+}
+
+int ceph_purge_inode_cap(struct inode *inode, struct ceph_cap *cap, bool *invalidate)
+{
+	struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
+	struct ceph_mds_client *mdsc = fsc->mdsc;
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	bool is_auth;
+	bool dirty_dropped = false;
+	int iputs = 0;
+
+	lockdep_assert_held(&ci->i_ceph_lock);
+
+	dout("removing cap %p, ci is %p, inode is %p\n",
+	     cap, ci, &ci->netfs.inode);
+
+	is_auth = (cap == ci->i_auth_cap);
+	__ceph_remove_cap(cap, false);
+	if (is_auth) {
+		struct ceph_cap_flush *cf;
+
+		if (ceph_inode_is_shutdown(inode)) {
+			if (inode->i_data.nrpages > 0)
+				*invalidate = true;
+			if (ci->i_wrbuffer_ref > 0)
+				mapping_set_error(&inode->i_data, -EIO);
+		}
+
+		spin_lock(&mdsc->cap_dirty_lock);
+
+		/* trash all of the cap flushes for this inode */
+		while (!list_empty(&ci->i_cap_flush_list)) {
+			cf = list_first_entry(&ci->i_cap_flush_list,
+					      struct ceph_cap_flush, i_list);
+			list_del_init(&cf->g_list);
+			list_del_init(&cf->i_list);
+			if (!cf->is_capsnap)
+				ceph_free_cap_flush(cf);
+		}
+
+		if (!list_empty(&ci->i_dirty_item)) {
+			pr_warn_ratelimited(
+				" dropping dirty %s state for %p %lld\n",
+				ceph_cap_string(ci->i_dirty_caps),
+				inode, ceph_ino(inode));
+			ci->i_dirty_caps = 0;
+			list_del_init(&ci->i_dirty_item);
+			dirty_dropped = true;
+		}
+		if (!list_empty(&ci->i_flushing_item)) {
+			pr_warn_ratelimited(
+				" dropping dirty+flushing %s state for %p %lld\n",
+				ceph_cap_string(ci->i_flushing_caps),
+				inode, ceph_ino(inode));
+			ci->i_flushing_caps = 0;
+			list_del_init(&ci->i_flushing_item);
+			mdsc->num_cap_flushing--;
+			dirty_dropped = true;
+		}
+		spin_unlock(&mdsc->cap_dirty_lock);
+
+		if (dirty_dropped) {
+			mapping_set_error(inode->i_mapping, -EIO);
+
+			if (ci->i_wrbuffer_ref_head == 0 &&
+			    ci->i_wr_ref == 0 &&
+			    ci->i_dirty_caps == 0 &&
+			    ci->i_flushing_caps == 0) {
+				ceph_put_snap_context(ci->i_head_snapc);
+				ci->i_head_snapc = NULL;
+			}
+		}
+
+		if (atomic_read(&ci->i_filelock_ref) > 0) {
+			/* make further file lock syscall return -EIO */
+			ci->i_ceph_flags |= CEPH_I_ERROR_FILELOCK;
+			pr_warn_ratelimited(" dropping file locks for %p %lld\n",
+					    inode, ceph_ino(inode));
+		}
+
+		if (!ci->i_dirty_caps && ci->i_prealloc_cap_flush) {
+			cf = ci->i_prealloc_cap_flush;
+			ci->i_prealloc_cap_flush = NULL;
+			if (!cf->is_capsnap)
+				ceph_free_cap_flush(cf);
+		}
+
+		if (!list_empty(&ci->i_cap_snaps))
+			iputs = remove_capsnaps(mdsc, inode);
+	}
+	if (dirty_dropped)
+		++iputs;
+	return iputs;
+}