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620 lines
14 KiB
620 lines
14 KiB
// 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 <[email protected]> |
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* Copyright 2001-2006 Ian Kent <[email protected]> |
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*/ |
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|
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#include "autofs_i.h" |
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|
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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 (simple_empty(dentry)) |
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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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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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/* 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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pr_debug("waiting for expire %p name=%pd\n", dentry, dentry); |
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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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pr_debug("expire done status=%d\n", status); |
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if (d_unhashed(dentry)) |
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return -EAGAIN; |
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return status; |
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} |
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spin_unlock(&sbi->fs_lock); |
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return 0; |
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} |
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/* Perform an expiry operation */ |
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int autofs_expire_run(struct super_block *sb, |
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struct vfsmount *mnt, |
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struct autofs_sb_info *sbi, |
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struct autofs_packet_expire __user *pkt_p) |
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{ |
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struct autofs_packet_expire pkt; |
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struct autofs_info *ino; |
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struct dentry *dentry; |
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int ret = 0; |
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memset(&pkt, 0, sizeof(pkt)); |
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pkt.hdr.proto_version = sbi->version; |
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pkt.hdr.type = autofs_ptype_expire; |
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dentry = autofs_expire_indirect(sb, mnt, sbi, 0); |
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if (!dentry) |
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return -EAGAIN; |
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pkt.len = dentry->d_name.len; |
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memcpy(pkt.name, dentry->d_name.name, pkt.len); |
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pkt.name[pkt.len] = '\0'; |
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if (copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire))) |
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ret = -EFAULT; |
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spin_lock(&sbi->fs_lock); |
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ino = autofs_dentry_ino(dentry); |
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/* avoid rapid-fire expire attempts if expiry fails */ |
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ino->last_used = jiffies; |
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ino->flags &= ~(AUTOFS_INF_EXPIRING|AUTOFS_INF_WANT_EXPIRE); |
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complete_all(&ino->expire_complete); |
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spin_unlock(&sbi->fs_lock); |
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dput(dentry); |
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return ret; |
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} |
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int autofs_do_expire_multi(struct super_block *sb, struct vfsmount *mnt, |
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struct autofs_sb_info *sbi, unsigned int how) |
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{ |
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struct dentry *dentry; |
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int ret = -EAGAIN; |
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if (autofs_type_trigger(sbi->type)) |
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dentry = autofs_expire_direct(sb, mnt, sbi, how); |
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else |
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dentry = autofs_expire_indirect(sb, mnt, sbi, how); |
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if (dentry) { |
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struct autofs_info *ino = autofs_dentry_ino(dentry); |
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const struct path path = { .mnt = mnt, .dentry = dentry }; |
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|
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/* This is synchronous because it makes the daemon a |
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* little easier |
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*/ |
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ret = autofs_wait(sbi, &path, NFY_EXPIRE); |
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|
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spin_lock(&sbi->fs_lock); |
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/* avoid rapid-fire expire attempts if expiry fails */ |
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ino->last_used = jiffies; |
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ino->flags &= ~(AUTOFS_INF_EXPIRING|AUTOFS_INF_WANT_EXPIRE); |
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complete_all(&ino->expire_complete); |
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spin_unlock(&sbi->fs_lock); |
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dput(dentry); |
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} |
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|
|
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); |
|
}
|
|
|