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