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-rw-r--r--fs/autofs/expire.c620
1 files changed, 620 insertions, 0 deletions
diff --git a/fs/autofs/expire.c b/fs/autofs/expire.c
new file mode 100644
index 000000000..038b3d2d9
--- /dev/null
+++ b/fs/autofs/expire.c
@@ -0,0 +1,620 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
+ * Copyright 1999-2000 Jeremy Fitzhardinge <jeremy@goop.org>
+ * Copyright 2001-2006 Ian Kent <raven@themaw.net>
+ */
+
+#include "autofs_i.h"
+
+/* Check if a dentry can be expired */
+static inline int autofs_can_expire(struct dentry *dentry,
+ unsigned long timeout, unsigned int how)
+{
+ struct autofs_info *ino = autofs_dentry_ino(dentry);
+
+ /* dentry in the process of being deleted */
+ if (ino == NULL)
+ return 0;
+
+ if (!(how & AUTOFS_EXP_IMMEDIATE)) {
+ /* Too young to die */
+ if (!timeout || time_after(ino->last_used + timeout, jiffies))
+ return 0;
+ }
+ return 1;
+}
+
+/* Check a mount point for busyness */
+static int autofs_mount_busy(struct vfsmount *mnt,
+ struct dentry *dentry, unsigned int how)
+{
+ struct dentry *top = dentry;
+ struct path path = {.mnt = mnt, .dentry = dentry};
+ int status = 1;
+
+ pr_debug("dentry %p %pd\n", dentry, dentry);
+
+ path_get(&path);
+
+ if (!follow_down_one(&path))
+ goto done;
+
+ if (is_autofs_dentry(path.dentry)) {
+ struct autofs_sb_info *sbi = autofs_sbi(path.dentry->d_sb);
+
+ /* This is an autofs submount, we can't expire it */
+ if (autofs_type_indirect(sbi->type))
+ goto done;
+ }
+
+ /* Not a submount, has a forced expire been requested */
+ if (how & AUTOFS_EXP_FORCED) {
+ status = 0;
+ goto done;
+ }
+
+ /* Update the expiry counter if fs is busy */
+ if (!may_umount_tree(path.mnt)) {
+ struct autofs_info *ino;
+
+ ino = autofs_dentry_ino(top);
+ ino->last_used = jiffies;
+ goto done;
+ }
+
+ status = 0;
+done:
+ pr_debug("returning = %d\n", status);
+ path_put(&path);
+ return status;
+}
+
+/* p->d_lock held */
+static struct dentry *positive_after(struct dentry *p, struct dentry *child)
+{
+ if (child)
+ child = list_next_entry(child, d_child);
+ else
+ child = list_first_entry(&p->d_subdirs, struct dentry, d_child);
+
+ list_for_each_entry_from(child, &p->d_subdirs, d_child) {
+ spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
+ if (simple_positive(child)) {
+ dget_dlock(child);
+ spin_unlock(&child->d_lock);
+ return child;
+ }
+ spin_unlock(&child->d_lock);
+ }
+
+ return NULL;
+}
+
+/*
+ * Calculate and dget next entry in the subdirs list under root.
+ */
+static struct dentry *get_next_positive_subdir(struct dentry *prev,
+ struct dentry *root)
+{
+ struct autofs_sb_info *sbi = autofs_sbi(root->d_sb);
+ struct dentry *q;
+
+ spin_lock(&sbi->lookup_lock);
+ spin_lock(&root->d_lock);
+ q = positive_after(root, prev);
+ spin_unlock(&root->d_lock);
+ spin_unlock(&sbi->lookup_lock);
+ dput(prev);
+ return q;
+}
+
+/*
+ * Calculate and dget next entry in top down tree traversal.
+ */
+static struct dentry *get_next_positive_dentry(struct dentry *prev,
+ struct dentry *root)
+{
+ struct autofs_sb_info *sbi = autofs_sbi(root->d_sb);
+ struct dentry *p = prev, *ret = NULL, *d = NULL;
+
+ if (prev == NULL)
+ return dget(root);
+
+ spin_lock(&sbi->lookup_lock);
+ spin_lock(&p->d_lock);
+ while (1) {
+ struct dentry *parent;
+
+ ret = positive_after(p, d);
+ if (ret || p == root)
+ break;
+ parent = p->d_parent;
+ spin_unlock(&p->d_lock);
+ spin_lock(&parent->d_lock);
+ d = p;
+ p = parent;
+ }
+ spin_unlock(&p->d_lock);
+ spin_unlock(&sbi->lookup_lock);
+ dput(prev);
+ return ret;
+}
+
+/*
+ * Check a direct mount point for busyness.
+ * Direct mounts have similar expiry semantics to tree mounts.
+ * The tree is not busy iff no mountpoints are busy and there are no
+ * autofs submounts.
+ */
+static int autofs_direct_busy(struct vfsmount *mnt,
+ struct dentry *top,
+ unsigned long timeout,
+ unsigned int how)
+{
+ pr_debug("top %p %pd\n", top, top);
+
+ /* Forced expire, user space handles busy mounts */
+ if (how & AUTOFS_EXP_FORCED)
+ return 0;
+
+ /* If it's busy update the expiry counters */
+ if (!may_umount_tree(mnt)) {
+ struct autofs_info *ino;
+
+ ino = autofs_dentry_ino(top);
+ if (ino)
+ ino->last_used = jiffies;
+ return 1;
+ }
+
+ /* Timeout of a direct mount is determined by its top dentry */
+ if (!autofs_can_expire(top, timeout, how))
+ return 1;
+
+ return 0;
+}
+
+/*
+ * Check a directory tree of mount points for busyness
+ * The tree is not busy iff no mountpoints are busy
+ */
+static int autofs_tree_busy(struct vfsmount *mnt,
+ struct dentry *top,
+ unsigned long timeout,
+ unsigned int how)
+{
+ struct autofs_info *top_ino = autofs_dentry_ino(top);
+ struct dentry *p;
+
+ pr_debug("top %p %pd\n", top, top);
+
+ /* Negative dentry - give up */
+ if (!simple_positive(top))
+ return 1;
+
+ p = NULL;
+ while ((p = get_next_positive_dentry(p, top))) {
+ pr_debug("dentry %p %pd\n", p, p);
+
+ /*
+ * Is someone visiting anywhere in the subtree ?
+ * If there's no mount we need to check the usage
+ * count for the autofs dentry.
+ * If the fs is busy update the expiry counter.
+ */
+ if (d_mountpoint(p)) {
+ if (autofs_mount_busy(mnt, p, how)) {
+ top_ino->last_used = jiffies;
+ dput(p);
+ return 1;
+ }
+ } else {
+ struct autofs_info *ino = autofs_dentry_ino(p);
+ unsigned int ino_count = READ_ONCE(ino->count);
+
+ /* allow for dget above and top is already dgot */
+ if (p == top)
+ ino_count += 2;
+ else
+ ino_count++;
+
+ if (d_count(p) > ino_count) {
+ top_ino->last_used = jiffies;
+ dput(p);
+ return 1;
+ }
+ }
+ }
+
+ /* Forced expire, user space handles busy mounts */
+ if (how & AUTOFS_EXP_FORCED)
+ return 0;
+
+ /* Timeout of a tree mount is ultimately determined by its top dentry */
+ if (!autofs_can_expire(top, timeout, how))
+ return 1;
+
+ return 0;
+}
+
+static struct dentry *autofs_check_leaves(struct vfsmount *mnt,
+ struct dentry *parent,
+ unsigned long timeout,
+ unsigned int how)
+{
+ struct dentry *p;
+
+ pr_debug("parent %p %pd\n", parent, parent);
+
+ p = NULL;
+ while ((p = get_next_positive_dentry(p, parent))) {
+ pr_debug("dentry %p %pd\n", p, p);
+
+ if (d_mountpoint(p)) {
+ /* Can we umount this guy */
+ if (autofs_mount_busy(mnt, p, how))
+ continue;
+
+ /* This isn't a submount so if a forced expire
+ * has been requested, user space handles busy
+ * mounts */
+ if (how & AUTOFS_EXP_FORCED)
+ return p;
+
+ /* Can we expire this guy */
+ if (autofs_can_expire(p, timeout, how))
+ return p;
+ }
+ }
+ return NULL;
+}
+
+/* Check if we can expire a direct mount (possibly a tree) */
+static struct dentry *autofs_expire_direct(struct super_block *sb,
+ struct vfsmount *mnt,
+ struct autofs_sb_info *sbi,
+ unsigned int how)
+{
+ struct dentry *root = dget(sb->s_root);
+ struct autofs_info *ino;
+ unsigned long timeout;
+
+ if (!root)
+ return NULL;
+
+ timeout = sbi->exp_timeout;
+
+ if (!autofs_direct_busy(mnt, root, timeout, how)) {
+ spin_lock(&sbi->fs_lock);
+ ino = autofs_dentry_ino(root);
+ /* No point expiring a pending mount */
+ if (ino->flags & AUTOFS_INF_PENDING) {
+ spin_unlock(&sbi->fs_lock);
+ goto out;
+ }
+ ino->flags |= AUTOFS_INF_WANT_EXPIRE;
+ spin_unlock(&sbi->fs_lock);
+ synchronize_rcu();
+ if (!autofs_direct_busy(mnt, root, timeout, how)) {
+ spin_lock(&sbi->fs_lock);
+ ino->flags |= AUTOFS_INF_EXPIRING;
+ init_completion(&ino->expire_complete);
+ spin_unlock(&sbi->fs_lock);
+ return root;
+ }
+ spin_lock(&sbi->fs_lock);
+ ino->flags &= ~AUTOFS_INF_WANT_EXPIRE;
+ spin_unlock(&sbi->fs_lock);
+ }
+out:
+ dput(root);
+
+ return NULL;
+}
+
+/* Check if 'dentry' should expire, or return a nearby
+ * dentry that is suitable.
+ * If returned dentry is different from arg dentry,
+ * then a dget() reference was taken, else not.
+ */
+static struct dentry *should_expire(struct dentry *dentry,
+ struct vfsmount *mnt,
+ unsigned long timeout,
+ unsigned int how)
+{
+ struct autofs_info *ino = autofs_dentry_ino(dentry);
+ unsigned int ino_count;
+
+ /* No point expiring a pending mount */
+ if (ino->flags & AUTOFS_INF_PENDING)
+ return NULL;
+
+ /*
+ * Case 1: (i) indirect mount or top level pseudo direct mount
+ * (autofs-4.1).
+ * (ii) indirect mount with offset mount, check the "/"
+ * offset (autofs-5.0+).
+ */
+ if (d_mountpoint(dentry)) {
+ pr_debug("checking mountpoint %p %pd\n", dentry, dentry);
+
+ /* Can we umount this guy */
+ if (autofs_mount_busy(mnt, dentry, how))
+ return NULL;
+
+ /* This isn't a submount so if a forced expire
+ * has been requested, user space handles busy
+ * mounts */
+ if (how & AUTOFS_EXP_FORCED)
+ return dentry;
+
+ /* Can we expire this guy */
+ if (autofs_can_expire(dentry, timeout, how))
+ return dentry;
+ return NULL;
+ }
+
+ if (d_is_symlink(dentry)) {
+ pr_debug("checking symlink %p %pd\n", dentry, dentry);
+
+ /* Forced expire, user space handles busy mounts */
+ if (how & AUTOFS_EXP_FORCED)
+ return dentry;
+
+ /*
+ * A symlink can't be "busy" in the usual sense so
+ * just check last used for expire timeout.
+ */
+ if (autofs_can_expire(dentry, timeout, how))
+ return dentry;
+ return NULL;
+ }
+
+ if (autofs_empty(ino))
+ return NULL;
+
+ /* Case 2: tree mount, expire iff entire tree is not busy */
+ if (!(how & AUTOFS_EXP_LEAVES)) {
+ /* Not a forced expire? */
+ if (!(how & AUTOFS_EXP_FORCED)) {
+ /* ref-walk currently on this dentry? */
+ ino_count = READ_ONCE(ino->count) + 1;
+ if (d_count(dentry) > ino_count)
+ return NULL;
+ }
+
+ if (!autofs_tree_busy(mnt, dentry, timeout, how))
+ return dentry;
+ /*
+ * Case 3: pseudo direct mount, expire individual leaves
+ * (autofs-4.1).
+ */
+ } else {
+ struct dentry *expired;
+
+ /* Not a forced expire? */
+ if (!(how & AUTOFS_EXP_FORCED)) {
+ /* ref-walk currently on this dentry? */
+ ino_count = READ_ONCE(ino->count) + 1;
+ if (d_count(dentry) > ino_count)
+ return NULL;
+ }
+
+ expired = autofs_check_leaves(mnt, dentry, timeout, how);
+ if (expired) {
+ if (expired == dentry)
+ dput(dentry);
+ return expired;
+ }
+ }
+ return NULL;
+}
+
+/*
+ * Find an eligible tree to time-out
+ * A tree is eligible if :-
+ * - it is unused by any user process
+ * - it has been unused for exp_timeout time
+ */
+static struct dentry *autofs_expire_indirect(struct super_block *sb,
+ struct vfsmount *mnt,
+ struct autofs_sb_info *sbi,
+ unsigned int how)
+{
+ unsigned long timeout;
+ struct dentry *root = sb->s_root;
+ struct dentry *dentry;
+ struct dentry *expired;
+ struct dentry *found;
+ struct autofs_info *ino;
+
+ if (!root)
+ return NULL;
+
+ timeout = sbi->exp_timeout;
+
+ dentry = NULL;
+ while ((dentry = get_next_positive_subdir(dentry, root))) {
+ spin_lock(&sbi->fs_lock);
+ ino = autofs_dentry_ino(dentry);
+ if (ino->flags & AUTOFS_INF_WANT_EXPIRE) {
+ spin_unlock(&sbi->fs_lock);
+ continue;
+ }
+ spin_unlock(&sbi->fs_lock);
+
+ expired = should_expire(dentry, mnt, timeout, how);
+ if (!expired)
+ continue;
+
+ spin_lock(&sbi->fs_lock);
+ ino = autofs_dentry_ino(expired);
+ ino->flags |= AUTOFS_INF_WANT_EXPIRE;
+ spin_unlock(&sbi->fs_lock);
+ synchronize_rcu();
+
+ /* Make sure a reference is not taken on found if
+ * things have changed.
+ */
+ how &= ~AUTOFS_EXP_LEAVES;
+ found = should_expire(expired, mnt, timeout, how);
+ if (found != expired) { // something has changed, continue
+ dput(found);
+ goto next;
+ }
+
+ if (expired != dentry)
+ dput(dentry);
+
+ spin_lock(&sbi->fs_lock);
+ goto found;
+next:
+ spin_lock(&sbi->fs_lock);
+ ino->flags &= ~AUTOFS_INF_WANT_EXPIRE;
+ spin_unlock(&sbi->fs_lock);
+ if (expired != dentry)
+ dput(expired);
+ }
+ return NULL;
+
+found:
+ pr_debug("returning %p %pd\n", expired, expired);
+ ino->flags |= AUTOFS_INF_EXPIRING;
+ init_completion(&ino->expire_complete);
+ spin_unlock(&sbi->fs_lock);
+ return expired;
+}
+
+int autofs_expire_wait(const struct path *path, int rcu_walk)
+{
+ struct dentry *dentry = path->dentry;
+ struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);
+ struct autofs_info *ino = autofs_dentry_ino(dentry);
+ int status;
+ int state;
+
+ /* Block on any pending expire */
+ if (!(ino->flags & AUTOFS_INF_WANT_EXPIRE))
+ return 0;
+ if (rcu_walk)
+ return -ECHILD;
+
+retry:
+ spin_lock(&sbi->fs_lock);
+ state = ino->flags & (AUTOFS_INF_WANT_EXPIRE | AUTOFS_INF_EXPIRING);
+ if (state == AUTOFS_INF_WANT_EXPIRE) {
+ spin_unlock(&sbi->fs_lock);
+ /*
+ * Possibly being selected for expire, wait until
+ * it's selected or not.
+ */
+ schedule_timeout_uninterruptible(HZ/10);
+ goto retry;
+ }
+ if (state & AUTOFS_INF_EXPIRING) {
+ spin_unlock(&sbi->fs_lock);
+
+ pr_debug("waiting for expire %p name=%pd\n", dentry, dentry);
+
+ status = autofs_wait(sbi, path, NFY_NONE);
+ wait_for_completion(&ino->expire_complete);
+
+ pr_debug("expire done status=%d\n", status);
+
+ if (d_unhashed(dentry))
+ return -EAGAIN;
+
+ return status;
+ }
+ spin_unlock(&sbi->fs_lock);
+
+ return 0;
+}
+
+/* Perform an expiry operation */
+int autofs_expire_run(struct super_block *sb,
+ struct vfsmount *mnt,
+ struct autofs_sb_info *sbi,
+ struct autofs_packet_expire __user *pkt_p)
+{
+ struct autofs_packet_expire pkt;
+ struct autofs_info *ino;
+ struct dentry *dentry;
+ int ret = 0;
+
+ memset(&pkt, 0, sizeof(pkt));
+
+ pkt.hdr.proto_version = sbi->version;
+ pkt.hdr.type = autofs_ptype_expire;
+
+ dentry = autofs_expire_indirect(sb, mnt, sbi, 0);
+ if (!dentry)
+ return -EAGAIN;
+
+ pkt.len = dentry->d_name.len;
+ memcpy(pkt.name, dentry->d_name.name, pkt.len);
+ pkt.name[pkt.len] = '\0';
+
+ if (copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)))
+ ret = -EFAULT;
+
+ spin_lock(&sbi->fs_lock);
+ ino = autofs_dentry_ino(dentry);
+ /* avoid rapid-fire expire attempts if expiry fails */
+ ino->last_used = jiffies;
+ ino->flags &= ~(AUTOFS_INF_EXPIRING|AUTOFS_INF_WANT_EXPIRE);
+ complete_all(&ino->expire_complete);
+ spin_unlock(&sbi->fs_lock);
+
+ dput(dentry);
+
+ return ret;
+}
+
+int autofs_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
+ struct autofs_sb_info *sbi, unsigned int how)
+{
+ struct dentry *dentry;
+ int ret = -EAGAIN;
+
+ if (autofs_type_trigger(sbi->type))
+ dentry = autofs_expire_direct(sb, mnt, sbi, how);
+ else
+ dentry = autofs_expire_indirect(sb, mnt, sbi, how);
+
+ if (dentry) {
+ struct autofs_info *ino = autofs_dentry_ino(dentry);
+ const struct path path = { .mnt = mnt, .dentry = dentry };
+
+ /* This is synchronous because it makes the daemon a
+ * little easier
+ */
+ ret = autofs_wait(sbi, &path, NFY_EXPIRE);
+
+ spin_lock(&sbi->fs_lock);
+ /* avoid rapid-fire expire attempts if expiry fails */
+ ino->last_used = jiffies;
+ ino->flags &= ~(AUTOFS_INF_EXPIRING|AUTOFS_INF_WANT_EXPIRE);
+ complete_all(&ino->expire_complete);
+ spin_unlock(&sbi->fs_lock);
+ dput(dentry);
+ }
+
+ return ret;
+}
+
+/*
+ * Call repeatedly until it returns -EAGAIN, meaning there's nothing
+ * more to be done.
+ */
+int autofs_expire_multi(struct super_block *sb, struct vfsmount *mnt,
+ struct autofs_sb_info *sbi, int __user *arg)
+{
+ unsigned int how = 0;
+
+ if (arg && get_user(how, arg))
+ return -EFAULT;
+
+ return autofs_do_expire_multi(sb, mnt, sbi, how);
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-03 04:36:14 +0000