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-rw-r--r--fs/notify/mark.c911
1 files changed, 911 insertions, 0 deletions
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
new file mode 100644
index 000000000..c74ef9474
--- /dev/null
+++ b/fs/notify/mark.c
@@ -0,0 +1,911 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
+ */
+
+/*
+ * fsnotify inode mark locking/lifetime/and refcnting
+ *
+ * REFCNT:
+ * The group->recnt and mark->refcnt tell how many "things" in the kernel
+ * currently are referencing the objects. Both kind of objects typically will
+ * live inside the kernel with a refcnt of 2, one for its creation and one for
+ * the reference a group and a mark hold to each other.
+ * If you are holding the appropriate locks, you can take a reference and the
+ * object itself is guaranteed to survive until the reference is dropped.
+ *
+ * LOCKING:
+ * There are 3 locks involved with fsnotify inode marks and they MUST be taken
+ * in order as follows:
+ *
+ * group->mark_mutex
+ * mark->lock
+ * mark->connector->lock
+ *
+ * group->mark_mutex protects the marks_list anchored inside a given group and
+ * each mark is hooked via the g_list. It also protects the groups private
+ * data (i.e group limits).
+
+ * mark->lock protects the marks attributes like its masks and flags.
+ * Furthermore it protects the access to a reference of the group that the mark
+ * is assigned to as well as the access to a reference of the inode/vfsmount
+ * that is being watched by the mark.
+ *
+ * mark->connector->lock protects the list of marks anchored inside an
+ * inode / vfsmount and each mark is hooked via the i_list.
+ *
+ * A list of notification marks relating to inode / mnt is contained in
+ * fsnotify_mark_connector. That structure is alive as long as there are any
+ * marks in the list and is also protected by fsnotify_mark_srcu. A mark gets
+ * detached from fsnotify_mark_connector when last reference to the mark is
+ * dropped. Thus having mark reference is enough to protect mark->connector
+ * pointer and to make sure fsnotify_mark_connector cannot disappear. Also
+ * because we remove mark from g_list before dropping mark reference associated
+ * with that, any mark found through g_list is guaranteed to have
+ * mark->connector set until we drop group->mark_mutex.
+ *
+ * LIFETIME:
+ * Inode marks survive between when they are added to an inode and when their
+ * refcnt==0. Marks are also protected by fsnotify_mark_srcu.
+ *
+ * The inode mark can be cleared for a number of different reasons including:
+ * - The inode is unlinked for the last time. (fsnotify_inode_remove)
+ * - The inode is being evicted from cache. (fsnotify_inode_delete)
+ * - The fs the inode is on is unmounted. (fsnotify_inode_delete/fsnotify_unmount_inodes)
+ * - Something explicitly requests that it be removed. (fsnotify_destroy_mark)
+ * - The fsnotify_group associated with the mark is going away and all such marks
+ * need to be cleaned up. (fsnotify_clear_marks_by_group)
+ *
+ * This has the very interesting property of being able to run concurrently with
+ * any (or all) other directions.
+ */
+
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/srcu.h>
+#include <linux/ratelimit.h>
+
+#include <linux/atomic.h>
+
+#include <linux/fsnotify_backend.h>
+#include "fsnotify.h"
+
+#define FSNOTIFY_REAPER_DELAY (1) /* 1 jiffy */
+
+struct srcu_struct fsnotify_mark_srcu;
+struct kmem_cache *fsnotify_mark_connector_cachep;
+
+static DEFINE_SPINLOCK(destroy_lock);
+static LIST_HEAD(destroy_list);
+static struct fsnotify_mark_connector *connector_destroy_list;
+
+static void fsnotify_mark_destroy_workfn(struct work_struct *work);
+static DECLARE_DELAYED_WORK(reaper_work, fsnotify_mark_destroy_workfn);
+
+static void fsnotify_connector_destroy_workfn(struct work_struct *work);
+static DECLARE_WORK(connector_reaper_work, fsnotify_connector_destroy_workfn);
+
+void fsnotify_get_mark(struct fsnotify_mark *mark)
+{
+ WARN_ON_ONCE(!refcount_read(&mark->refcnt));
+ refcount_inc(&mark->refcnt);
+}
+
+static __u32 *fsnotify_conn_mask_p(struct fsnotify_mark_connector *conn)
+{
+ if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
+ return &fsnotify_conn_inode(conn)->i_fsnotify_mask;
+ else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT)
+ return &fsnotify_conn_mount(conn)->mnt_fsnotify_mask;
+ else if (conn->type == FSNOTIFY_OBJ_TYPE_SB)
+ return &fsnotify_conn_sb(conn)->s_fsnotify_mask;
+ return NULL;
+}
+
+__u32 fsnotify_conn_mask(struct fsnotify_mark_connector *conn)
+{
+ if (WARN_ON(!fsnotify_valid_obj_type(conn->type)))
+ return 0;
+
+ return *fsnotify_conn_mask_p(conn);
+}
+
+static void fsnotify_get_inode_ref(struct inode *inode)
+{
+ ihold(inode);
+ atomic_long_inc(&inode->i_sb->s_fsnotify_connectors);
+}
+
+/*
+ * Grab or drop inode reference for the connector if needed.
+ *
+ * When it's time to drop the reference, we only clear the HAS_IREF flag and
+ * return the inode object. fsnotify_drop_object() will be resonsible for doing
+ * iput() outside of spinlocks. This happens when last mark that wanted iref is
+ * detached.
+ */
+static struct inode *fsnotify_update_iref(struct fsnotify_mark_connector *conn,
+ bool want_iref)
+{
+ bool has_iref = conn->flags & FSNOTIFY_CONN_FLAG_HAS_IREF;
+ struct inode *inode = NULL;
+
+ if (conn->type != FSNOTIFY_OBJ_TYPE_INODE ||
+ want_iref == has_iref)
+ return NULL;
+
+ if (want_iref) {
+ /* Pin inode if any mark wants inode refcount held */
+ fsnotify_get_inode_ref(fsnotify_conn_inode(conn));
+ conn->flags |= FSNOTIFY_CONN_FLAG_HAS_IREF;
+ } else {
+ /* Unpin inode after detach of last mark that wanted iref */
+ inode = fsnotify_conn_inode(conn);
+ conn->flags &= ~FSNOTIFY_CONN_FLAG_HAS_IREF;
+ }
+
+ return inode;
+}
+
+static void *__fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
+{
+ u32 new_mask = 0;
+ bool want_iref = false;
+ struct fsnotify_mark *mark;
+
+ assert_spin_locked(&conn->lock);
+ /* We can get detached connector here when inode is getting unlinked. */
+ if (!fsnotify_valid_obj_type(conn->type))
+ return NULL;
+ hlist_for_each_entry(mark, &conn->list, obj_list) {
+ if (!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED))
+ continue;
+ new_mask |= fsnotify_calc_mask(mark);
+ if (conn->type == FSNOTIFY_OBJ_TYPE_INODE &&
+ !(mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF))
+ want_iref = true;
+ }
+ *fsnotify_conn_mask_p(conn) = new_mask;
+
+ return fsnotify_update_iref(conn, want_iref);
+}
+
+/*
+ * Calculate mask of events for a list of marks. The caller must make sure
+ * connector and connector->obj cannot disappear under us. Callers achieve
+ * this by holding a mark->lock or mark->group->mark_mutex for a mark on this
+ * list.
+ */
+void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
+{
+ if (!conn)
+ return;
+
+ spin_lock(&conn->lock);
+ __fsnotify_recalc_mask(conn);
+ spin_unlock(&conn->lock);
+ if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
+ __fsnotify_update_child_dentry_flags(
+ fsnotify_conn_inode(conn));
+}
+
+/* Free all connectors queued for freeing once SRCU period ends */
+static void fsnotify_connector_destroy_workfn(struct work_struct *work)
+{
+ struct fsnotify_mark_connector *conn, *free;
+
+ spin_lock(&destroy_lock);
+ conn = connector_destroy_list;
+ connector_destroy_list = NULL;
+ spin_unlock(&destroy_lock);
+
+ synchronize_srcu(&fsnotify_mark_srcu);
+ while (conn) {
+ free = conn;
+ conn = conn->destroy_next;
+ kmem_cache_free(fsnotify_mark_connector_cachep, free);
+ }
+}
+
+static void fsnotify_put_inode_ref(struct inode *inode)
+{
+ struct super_block *sb = inode->i_sb;
+
+ iput(inode);
+ if (atomic_long_dec_and_test(&sb->s_fsnotify_connectors))
+ wake_up_var(&sb->s_fsnotify_connectors);
+}
+
+static void fsnotify_get_sb_connectors(struct fsnotify_mark_connector *conn)
+{
+ struct super_block *sb = fsnotify_connector_sb(conn);
+
+ if (sb)
+ atomic_long_inc(&sb->s_fsnotify_connectors);
+}
+
+static void fsnotify_put_sb_connectors(struct fsnotify_mark_connector *conn)
+{
+ struct super_block *sb = fsnotify_connector_sb(conn);
+
+ if (sb && atomic_long_dec_and_test(&sb->s_fsnotify_connectors))
+ wake_up_var(&sb->s_fsnotify_connectors);
+}
+
+static void *fsnotify_detach_connector_from_object(
+ struct fsnotify_mark_connector *conn,
+ unsigned int *type)
+{
+ struct inode *inode = NULL;
+
+ *type = conn->type;
+ if (conn->type == FSNOTIFY_OBJ_TYPE_DETACHED)
+ return NULL;
+
+ if (conn->type == FSNOTIFY_OBJ_TYPE_INODE) {
+ inode = fsnotify_conn_inode(conn);
+ inode->i_fsnotify_mask = 0;
+
+ /* Unpin inode when detaching from connector */
+ if (!(conn->flags & FSNOTIFY_CONN_FLAG_HAS_IREF))
+ inode = NULL;
+ } else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT) {
+ fsnotify_conn_mount(conn)->mnt_fsnotify_mask = 0;
+ } else if (conn->type == FSNOTIFY_OBJ_TYPE_SB) {
+ fsnotify_conn_sb(conn)->s_fsnotify_mask = 0;
+ }
+
+ fsnotify_put_sb_connectors(conn);
+ rcu_assign_pointer(*(conn->obj), NULL);
+ conn->obj = NULL;
+ conn->type = FSNOTIFY_OBJ_TYPE_DETACHED;
+
+ return inode;
+}
+
+static void fsnotify_final_mark_destroy(struct fsnotify_mark *mark)
+{
+ struct fsnotify_group *group = mark->group;
+
+ if (WARN_ON_ONCE(!group))
+ return;
+ group->ops->free_mark(mark);
+ fsnotify_put_group(group);
+}
+
+/* Drop object reference originally held by a connector */
+static void fsnotify_drop_object(unsigned int type, void *objp)
+{
+ if (!objp)
+ return;
+ /* Currently only inode references are passed to be dropped */
+ if (WARN_ON_ONCE(type != FSNOTIFY_OBJ_TYPE_INODE))
+ return;
+ fsnotify_put_inode_ref(objp);
+}
+
+void fsnotify_put_mark(struct fsnotify_mark *mark)
+{
+ struct fsnotify_mark_connector *conn = READ_ONCE(mark->connector);
+ void *objp = NULL;
+ unsigned int type = FSNOTIFY_OBJ_TYPE_DETACHED;
+ bool free_conn = false;
+
+ /* Catch marks that were actually never attached to object */
+ if (!conn) {
+ if (refcount_dec_and_test(&mark->refcnt))
+ fsnotify_final_mark_destroy(mark);
+ return;
+ }
+
+ /*
+ * We have to be careful so that traversals of obj_list under lock can
+ * safely grab mark reference.
+ */
+ if (!refcount_dec_and_lock(&mark->refcnt, &conn->lock))
+ return;
+
+ hlist_del_init_rcu(&mark->obj_list);
+ if (hlist_empty(&conn->list)) {
+ objp = fsnotify_detach_connector_from_object(conn, &type);
+ free_conn = true;
+ } else {
+ objp = __fsnotify_recalc_mask(conn);
+ type = conn->type;
+ }
+ WRITE_ONCE(mark->connector, NULL);
+ spin_unlock(&conn->lock);
+
+ fsnotify_drop_object(type, objp);
+
+ if (free_conn) {
+ spin_lock(&destroy_lock);
+ conn->destroy_next = connector_destroy_list;
+ connector_destroy_list = conn;
+ spin_unlock(&destroy_lock);
+ queue_work(system_unbound_wq, &connector_reaper_work);
+ }
+ /*
+ * Note that we didn't update flags telling whether inode cares about
+ * what's happening with children. We update these flags from
+ * __fsnotify_parent() lazily when next event happens on one of our
+ * children.
+ */
+ spin_lock(&destroy_lock);
+ list_add(&mark->g_list, &destroy_list);
+ spin_unlock(&destroy_lock);
+ queue_delayed_work(system_unbound_wq, &reaper_work,
+ FSNOTIFY_REAPER_DELAY);
+}
+EXPORT_SYMBOL_GPL(fsnotify_put_mark);
+
+/*
+ * Get mark reference when we found the mark via lockless traversal of object
+ * list. Mark can be already removed from the list by now and on its way to be
+ * destroyed once SRCU period ends.
+ *
+ * Also pin the group so it doesn't disappear under us.
+ */
+static bool fsnotify_get_mark_safe(struct fsnotify_mark *mark)
+{
+ if (!mark)
+ return true;
+
+ if (refcount_inc_not_zero(&mark->refcnt)) {
+ spin_lock(&mark->lock);
+ if (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) {
+ /* mark is attached, group is still alive then */
+ atomic_inc(&mark->group->user_waits);
+ spin_unlock(&mark->lock);
+ return true;
+ }
+ spin_unlock(&mark->lock);
+ fsnotify_put_mark(mark);
+ }
+ return false;
+}
+
+/*
+ * Puts marks and wakes up group destruction if necessary.
+ *
+ * Pairs with fsnotify_get_mark_safe()
+ */
+static void fsnotify_put_mark_wake(struct fsnotify_mark *mark)
+{
+ if (mark) {
+ struct fsnotify_group *group = mark->group;
+
+ fsnotify_put_mark(mark);
+ /*
+ * We abuse notification_waitq on group shutdown for waiting for
+ * all marks pinned when waiting for userspace.
+ */
+ if (atomic_dec_and_test(&group->user_waits) && group->shutdown)
+ wake_up(&group->notification_waitq);
+ }
+}
+
+bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info)
+ __releases(&fsnotify_mark_srcu)
+{
+ int type;
+
+ fsnotify_foreach_iter_type(type) {
+ /* This can fail if mark is being removed */
+ if (!fsnotify_get_mark_safe(iter_info->marks[type])) {
+ __release(&fsnotify_mark_srcu);
+ goto fail;
+ }
+ }
+
+ /*
+ * Now that both marks are pinned by refcount in the inode / vfsmount
+ * lists, we can drop SRCU lock, and safely resume the list iteration
+ * once userspace returns.
+ */
+ srcu_read_unlock(&fsnotify_mark_srcu, iter_info->srcu_idx);
+
+ return true;
+
+fail:
+ for (type--; type >= 0; type--)
+ fsnotify_put_mark_wake(iter_info->marks[type]);
+ return false;
+}
+
+void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info)
+ __acquires(&fsnotify_mark_srcu)
+{
+ int type;
+
+ iter_info->srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);
+ fsnotify_foreach_iter_type(type)
+ fsnotify_put_mark_wake(iter_info->marks[type]);
+}
+
+/*
+ * Mark mark as detached, remove it from group list. Mark still stays in object
+ * list until its last reference is dropped. Note that we rely on mark being
+ * removed from group list before corresponding reference to it is dropped. In
+ * particular we rely on mark->connector being valid while we hold
+ * group->mark_mutex if we found the mark through g_list.
+ *
+ * Must be called with group->mark_mutex held. The caller must either hold
+ * reference to the mark or be protected by fsnotify_mark_srcu.
+ */
+void fsnotify_detach_mark(struct fsnotify_mark *mark)
+{
+ fsnotify_group_assert_locked(mark->group);
+ WARN_ON_ONCE(!srcu_read_lock_held(&fsnotify_mark_srcu) &&
+ refcount_read(&mark->refcnt) < 1 +
+ !!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED));
+
+ spin_lock(&mark->lock);
+ /* something else already called this function on this mark */
+ if (!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
+ spin_unlock(&mark->lock);
+ return;
+ }
+ mark->flags &= ~FSNOTIFY_MARK_FLAG_ATTACHED;
+ list_del_init(&mark->g_list);
+ spin_unlock(&mark->lock);
+
+ /* Drop mark reference acquired in fsnotify_add_mark_locked() */
+ fsnotify_put_mark(mark);
+}
+
+/*
+ * Free fsnotify mark. The mark is actually only marked as being freed. The
+ * freeing is actually happening only once last reference to the mark is
+ * dropped from a workqueue which first waits for srcu period end.
+ *
+ * Caller must have a reference to the mark or be protected by
+ * fsnotify_mark_srcu.
+ */
+void fsnotify_free_mark(struct fsnotify_mark *mark)
+{
+ struct fsnotify_group *group = mark->group;
+
+ spin_lock(&mark->lock);
+ /* something else already called this function on this mark */
+ if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
+ spin_unlock(&mark->lock);
+ return;
+ }
+ mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
+ spin_unlock(&mark->lock);
+
+ /*
+ * Some groups like to know that marks are being freed. This is a
+ * callback to the group function to let it know that this mark
+ * is being freed.
+ */
+ if (group->ops->freeing_mark)
+ group->ops->freeing_mark(mark, group);
+}
+
+void fsnotify_destroy_mark(struct fsnotify_mark *mark,
+ struct fsnotify_group *group)
+{
+ fsnotify_group_lock(group);
+ fsnotify_detach_mark(mark);
+ fsnotify_group_unlock(group);
+ fsnotify_free_mark(mark);
+}
+EXPORT_SYMBOL_GPL(fsnotify_destroy_mark);
+
+/*
+ * Sorting function for lists of fsnotify marks.
+ *
+ * Fanotify supports different notification classes (reflected as priority of
+ * notification group). Events shall be passed to notification groups in
+ * decreasing priority order. To achieve this marks in notification lists for
+ * inodes and vfsmounts are sorted so that priorities of corresponding groups
+ * are descending.
+ *
+ * Furthermore correct handling of the ignore mask requires processing inode
+ * and vfsmount marks of each group together. Using the group address as
+ * further sort criterion provides a unique sorting order and thus we can
+ * merge inode and vfsmount lists of marks in linear time and find groups
+ * present in both lists.
+ *
+ * A return value of 1 signifies that b has priority over a.
+ * A return value of 0 signifies that the two marks have to be handled together.
+ * A return value of -1 signifies that a has priority over b.
+ */
+int fsnotify_compare_groups(struct fsnotify_group *a, struct fsnotify_group *b)
+{
+ if (a == b)
+ return 0;
+ if (!a)
+ return 1;
+ if (!b)
+ return -1;
+ if (a->priority < b->priority)
+ return 1;
+ if (a->priority > b->priority)
+ return -1;
+ if (a < b)
+ return 1;
+ return -1;
+}
+
+static int fsnotify_attach_connector_to_object(fsnotify_connp_t *connp,
+ unsigned int obj_type,
+ __kernel_fsid_t *fsid)
+{
+ struct fsnotify_mark_connector *conn;
+
+ conn = kmem_cache_alloc(fsnotify_mark_connector_cachep, GFP_KERNEL);
+ if (!conn)
+ return -ENOMEM;
+ spin_lock_init(&conn->lock);
+ INIT_HLIST_HEAD(&conn->list);
+ conn->flags = 0;
+ conn->type = obj_type;
+ conn->obj = connp;
+ /* Cache fsid of filesystem containing the object */
+ if (fsid) {
+ conn->fsid = *fsid;
+ conn->flags = FSNOTIFY_CONN_FLAG_HAS_FSID;
+ } else {
+ conn->fsid.val[0] = conn->fsid.val[1] = 0;
+ conn->flags = 0;
+ }
+ fsnotify_get_sb_connectors(conn);
+
+ /*
+ * cmpxchg() provides the barrier so that readers of *connp can see
+ * only initialized structure
+ */
+ if (cmpxchg(connp, NULL, conn)) {
+ /* Someone else created list structure for us */
+ fsnotify_put_sb_connectors(conn);
+ kmem_cache_free(fsnotify_mark_connector_cachep, conn);
+ }
+
+ return 0;
+}
+
+/*
+ * Get mark connector, make sure it is alive and return with its lock held.
+ * This is for users that get connector pointer from inode or mount. Users that
+ * hold reference to a mark on the list may directly lock connector->lock as
+ * they are sure list cannot go away under them.
+ */
+static struct fsnotify_mark_connector *fsnotify_grab_connector(
+ fsnotify_connp_t *connp)
+{
+ struct fsnotify_mark_connector *conn;
+ int idx;
+
+ idx = srcu_read_lock(&fsnotify_mark_srcu);
+ conn = srcu_dereference(*connp, &fsnotify_mark_srcu);
+ if (!conn)
+ goto out;
+ spin_lock(&conn->lock);
+ if (conn->type == FSNOTIFY_OBJ_TYPE_DETACHED) {
+ spin_unlock(&conn->lock);
+ srcu_read_unlock(&fsnotify_mark_srcu, idx);
+ return NULL;
+ }
+out:
+ srcu_read_unlock(&fsnotify_mark_srcu, idx);
+ return conn;
+}
+
+/*
+ * Add mark into proper place in given list of marks. These marks may be used
+ * for the fsnotify backend to determine which event types should be delivered
+ * to which group and for which inodes. These marks are ordered according to
+ * priority, highest number first, and then by the group's location in memory.
+ */
+static int fsnotify_add_mark_list(struct fsnotify_mark *mark,
+ fsnotify_connp_t *connp,
+ unsigned int obj_type,
+ int add_flags, __kernel_fsid_t *fsid)
+{
+ struct fsnotify_mark *lmark, *last = NULL;
+ struct fsnotify_mark_connector *conn;
+ int cmp;
+ int err = 0;
+
+ if (WARN_ON(!fsnotify_valid_obj_type(obj_type)))
+ return -EINVAL;
+
+ /* Backend is expected to check for zero fsid (e.g. tmpfs) */
+ if (fsid && WARN_ON_ONCE(!fsid->val[0] && !fsid->val[1]))
+ return -ENODEV;
+
+restart:
+ spin_lock(&mark->lock);
+ conn = fsnotify_grab_connector(connp);
+ if (!conn) {
+ spin_unlock(&mark->lock);
+ err = fsnotify_attach_connector_to_object(connp, obj_type,
+ fsid);
+ if (err)
+ return err;
+ goto restart;
+ } else if (fsid && !(conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID)) {
+ conn->fsid = *fsid;
+ /* Pairs with smp_rmb() in fanotify_get_fsid() */
+ smp_wmb();
+ conn->flags |= FSNOTIFY_CONN_FLAG_HAS_FSID;
+ } else if (fsid && (conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID) &&
+ (fsid->val[0] != conn->fsid.val[0] ||
+ fsid->val[1] != conn->fsid.val[1])) {
+ /*
+ * Backend is expected to check for non uniform fsid
+ * (e.g. btrfs), but maybe we missed something?
+ * Only allow setting conn->fsid once to non zero fsid.
+ * inotify and non-fid fanotify groups do not set nor test
+ * conn->fsid.
+ */
+ pr_warn_ratelimited("%s: fsid mismatch on object of type %u: "
+ "%x.%x != %x.%x\n", __func__, conn->type,
+ fsid->val[0], fsid->val[1],
+ conn->fsid.val[0], conn->fsid.val[1]);
+ err = -EXDEV;
+ goto out_err;
+ }
+
+ /* is mark the first mark? */
+ if (hlist_empty(&conn->list)) {
+ hlist_add_head_rcu(&mark->obj_list, &conn->list);
+ goto added;
+ }
+
+ /* should mark be in the middle of the current list? */
+ hlist_for_each_entry(lmark, &conn->list, obj_list) {
+ last = lmark;
+
+ if ((lmark->group == mark->group) &&
+ (lmark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) &&
+ !(mark->group->flags & FSNOTIFY_GROUP_DUPS)) {
+ err = -EEXIST;
+ goto out_err;
+ }
+
+ cmp = fsnotify_compare_groups(lmark->group, mark->group);
+ if (cmp >= 0) {
+ hlist_add_before_rcu(&mark->obj_list, &lmark->obj_list);
+ goto added;
+ }
+ }
+
+ BUG_ON(last == NULL);
+ /* mark should be the last entry. last is the current last entry */
+ hlist_add_behind_rcu(&mark->obj_list, &last->obj_list);
+added:
+ /*
+ * Since connector is attached to object using cmpxchg() we are
+ * guaranteed that connector initialization is fully visible by anyone
+ * seeing mark->connector set.
+ */
+ WRITE_ONCE(mark->connector, conn);
+out_err:
+ spin_unlock(&conn->lock);
+ spin_unlock(&mark->lock);
+ return err;
+}
+
+/*
+ * Attach an initialized mark to a given group and fs object.
+ * These marks may be used for the fsnotify backend to determine which
+ * event types should be delivered to which group.
+ */
+int fsnotify_add_mark_locked(struct fsnotify_mark *mark,
+ fsnotify_connp_t *connp, unsigned int obj_type,
+ int add_flags, __kernel_fsid_t *fsid)
+{
+ struct fsnotify_group *group = mark->group;
+ int ret = 0;
+
+ fsnotify_group_assert_locked(group);
+
+ /*
+ * LOCKING ORDER!!!!
+ * group->mark_mutex
+ * mark->lock
+ * mark->connector->lock
+ */
+ spin_lock(&mark->lock);
+ mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE | FSNOTIFY_MARK_FLAG_ATTACHED;
+
+ list_add(&mark->g_list, &group->marks_list);
+ fsnotify_get_mark(mark); /* for g_list */
+ spin_unlock(&mark->lock);
+
+ ret = fsnotify_add_mark_list(mark, connp, obj_type, add_flags, fsid);
+ if (ret)
+ goto err;
+
+ fsnotify_recalc_mask(mark->connector);
+
+ return ret;
+err:
+ spin_lock(&mark->lock);
+ mark->flags &= ~(FSNOTIFY_MARK_FLAG_ALIVE |
+ FSNOTIFY_MARK_FLAG_ATTACHED);
+ list_del_init(&mark->g_list);
+ spin_unlock(&mark->lock);
+
+ fsnotify_put_mark(mark);
+ return ret;
+}
+
+int fsnotify_add_mark(struct fsnotify_mark *mark, fsnotify_connp_t *connp,
+ unsigned int obj_type, int add_flags,
+ __kernel_fsid_t *fsid)
+{
+ int ret;
+ struct fsnotify_group *group = mark->group;
+
+ fsnotify_group_lock(group);
+ ret = fsnotify_add_mark_locked(mark, connp, obj_type, add_flags, fsid);
+ fsnotify_group_unlock(group);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(fsnotify_add_mark);
+
+/*
+ * Given a list of marks, find the mark associated with given group. If found
+ * take a reference to that mark and return it, else return NULL.
+ */
+struct fsnotify_mark *fsnotify_find_mark(fsnotify_connp_t *connp,
+ struct fsnotify_group *group)
+{
+ struct fsnotify_mark_connector *conn;
+ struct fsnotify_mark *mark;
+
+ conn = fsnotify_grab_connector(connp);
+ if (!conn)
+ return NULL;
+
+ hlist_for_each_entry(mark, &conn->list, obj_list) {
+ if (mark->group == group &&
+ (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
+ fsnotify_get_mark(mark);
+ spin_unlock(&conn->lock);
+ return mark;
+ }
+ }
+ spin_unlock(&conn->lock);
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(fsnotify_find_mark);
+
+/* Clear any marks in a group with given type mask */
+void fsnotify_clear_marks_by_group(struct fsnotify_group *group,
+ unsigned int obj_type)
+{
+ struct fsnotify_mark *lmark, *mark;
+ LIST_HEAD(to_free);
+ struct list_head *head = &to_free;
+
+ /* Skip selection step if we want to clear all marks. */
+ if (obj_type == FSNOTIFY_OBJ_TYPE_ANY) {
+ head = &group->marks_list;
+ goto clear;
+ }
+ /*
+ * We have to be really careful here. Anytime we drop mark_mutex, e.g.
+ * fsnotify_clear_marks_by_inode() can come and free marks. Even in our
+ * to_free list so we have to use mark_mutex even when accessing that
+ * list. And freeing mark requires us to drop mark_mutex. So we can
+ * reliably free only the first mark in the list. That's why we first
+ * move marks to free to to_free list in one go and then free marks in
+ * to_free list one by one.
+ */
+ fsnotify_group_lock(group);
+ list_for_each_entry_safe(mark, lmark, &group->marks_list, g_list) {
+ if (mark->connector->type == obj_type)
+ list_move(&mark->g_list, &to_free);
+ }
+ fsnotify_group_unlock(group);
+
+clear:
+ while (1) {
+ fsnotify_group_lock(group);
+ if (list_empty(head)) {
+ fsnotify_group_unlock(group);
+ break;
+ }
+ mark = list_first_entry(head, struct fsnotify_mark, g_list);
+ fsnotify_get_mark(mark);
+ fsnotify_detach_mark(mark);
+ fsnotify_group_unlock(group);
+ fsnotify_free_mark(mark);
+ fsnotify_put_mark(mark);
+ }
+}
+
+/* Destroy all marks attached to an object via connector */
+void fsnotify_destroy_marks(fsnotify_connp_t *connp)
+{
+ struct fsnotify_mark_connector *conn;
+ struct fsnotify_mark *mark, *old_mark = NULL;
+ void *objp;
+ unsigned int type;
+
+ conn = fsnotify_grab_connector(connp);
+ if (!conn)
+ return;
+ /*
+ * We have to be careful since we can race with e.g.
+ * fsnotify_clear_marks_by_group() and once we drop the conn->lock, the
+ * list can get modified. However we are holding mark reference and
+ * thus our mark cannot be removed from obj_list so we can continue
+ * iteration after regaining conn->lock.
+ */
+ hlist_for_each_entry(mark, &conn->list, obj_list) {
+ fsnotify_get_mark(mark);
+ spin_unlock(&conn->lock);
+ if (old_mark)
+ fsnotify_put_mark(old_mark);
+ old_mark = mark;
+ fsnotify_destroy_mark(mark, mark->group);
+ spin_lock(&conn->lock);
+ }
+ /*
+ * Detach list from object now so that we don't pin inode until all
+ * mark references get dropped. It would lead to strange results such
+ * as delaying inode deletion or blocking unmount.
+ */
+ objp = fsnotify_detach_connector_from_object(conn, &type);
+ spin_unlock(&conn->lock);
+ if (old_mark)
+ fsnotify_put_mark(old_mark);
+ fsnotify_drop_object(type, objp);
+}
+
+/*
+ * Nothing fancy, just initialize lists and locks and counters.
+ */
+void fsnotify_init_mark(struct fsnotify_mark *mark,
+ struct fsnotify_group *group)
+{
+ memset(mark, 0, sizeof(*mark));
+ spin_lock_init(&mark->lock);
+ refcount_set(&mark->refcnt, 1);
+ fsnotify_get_group(group);
+ mark->group = group;
+ WRITE_ONCE(mark->connector, NULL);
+}
+EXPORT_SYMBOL_GPL(fsnotify_init_mark);
+
+/*
+ * Destroy all marks in destroy_list, waits for SRCU period to finish before
+ * actually freeing marks.
+ */
+static void fsnotify_mark_destroy_workfn(struct work_struct *work)
+{
+ struct fsnotify_mark *mark, *next;
+ struct list_head private_destroy_list;
+
+ spin_lock(&destroy_lock);
+ /* exchange the list head */
+ list_replace_init(&destroy_list, &private_destroy_list);
+ spin_unlock(&destroy_lock);
+
+ synchronize_srcu(&fsnotify_mark_srcu);
+
+ list_for_each_entry_safe(mark, next, &private_destroy_list, g_list) {
+ list_del_init(&mark->g_list);
+ fsnotify_final_mark_destroy(mark);
+ }
+}
+
+/* Wait for all marks queued for destruction to be actually destroyed */
+void fsnotify_wait_marks_destroyed(void)
+{
+ flush_delayed_work(&reaper_work);
+}
+EXPORT_SYMBOL_GPL(fsnotify_wait_marks_destroyed);
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-03 13:41:01 +0000