Fix the case where an expire returns busy on a tree mount when it is in fact not busy. This case was overlooked when the patch to prevent the expiring away of "scaffolding" directories for tree mounts was applied. The problem arises when a tree of mounts is a member of a map with other keys. The current logic will not expire the tree if any other mount in the map is busy. The solution is to maintain a "minimum" use count for each autofs dentry and compare this to the actual dentry usage count during expire. Signed-off-by: Ian Kent <raven@themaw.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
360 lines
8.4 KiB
C
360 lines
8.4 KiB
C
/* -*- c -*- --------------------------------------------------------------- *
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*
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* linux/fs/autofs/expire.c
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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 2001-2003 Ian Kent <raven@themaw.net>
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*
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* This file is part of the Linux kernel and is made available under
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* the terms of the GNU General Public License, version 2, or at your
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* option, any later version, incorporated herein by reference.
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*
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* ------------------------------------------------------------------------- */
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#include "autofs_i.h"
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static unsigned long now;
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/* Check if a dentry can be expired */
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static inline int autofs4_can_expire(struct dentry *dentry,
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unsigned long timeout, int do_now)
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{
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struct autofs_info *ino = autofs4_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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/* No point expiring a pending mount */
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if (dentry->d_flags & DCACHE_AUTOFS_PENDING)
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return 0;
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if (!do_now) {
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/* Too young to die */
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if (time_after(ino->last_used + timeout, now))
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return 0;
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/* update last_used here :-
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- obviously makes sense if it is in use now
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- less obviously, prevents rapid-fire expire
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attempts if expire fails the first time */
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ino->last_used = now;
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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 autofs4_mount_busy(struct vfsmount *mnt, struct dentry *dentry)
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{
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int status = 1;
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DPRINTK("dentry %p %.*s",
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dentry, (int)dentry->d_name.len, dentry->d_name.name);
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mntget(mnt);
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dget(dentry);
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if (!autofs4_follow_mount(&mnt, &dentry))
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goto done;
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/* This is an autofs submount, we can't expire it */
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if (is_autofs4_dentry(dentry))
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goto done;
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/* The big question */
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if (may_umount_tree(mnt) == 0)
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status = 0;
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done:
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DPRINTK("returning = %d", status);
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mntput(mnt);
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dput(dentry);
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return status;
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}
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/*
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* Calculate next entry in top down tree traversal.
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* From next_mnt in namespace.c - elegant.
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*/
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static struct dentry *next_dentry(struct dentry *p, struct dentry *root)
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{
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struct list_head *next = p->d_subdirs.next;
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if (next == &p->d_subdirs) {
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while (1) {
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if (p == root)
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return NULL;
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next = p->d_u.d_child.next;
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if (next != &p->d_parent->d_subdirs)
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break;
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p = p->d_parent;
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}
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}
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return list_entry(next, struct dentry, d_u.d_child);
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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 autofs4_tree_busy(struct vfsmount *mnt,
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struct dentry *top,
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unsigned long timeout,
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int do_now)
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{
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struct autofs_info *ino;
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struct dentry *p;
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DPRINTK("top %p %.*s",
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top, (int)top->d_name.len, top->d_name.name);
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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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spin_lock(&dcache_lock);
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for (p = top; p; p = next_dentry(p, top)) {
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/* Negative dentry - give up */
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if (!simple_positive(p))
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continue;
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DPRINTK("dentry %p %.*s",
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p, (int) p->d_name.len, p->d_name.name);
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p = dget(p);
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spin_unlock(&dcache_lock);
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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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*/
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ino = autofs4_dentry_ino(p);
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if (d_mountpoint(p)) {
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if (autofs4_mount_busy(mnt, p)) {
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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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unsigned int ino_count = atomic_read(&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 (atomic_read(&p->d_count) > ino_count) {
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dput(p);
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return 1;
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}
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}
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dput(p);
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spin_lock(&dcache_lock);
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}
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spin_unlock(&dcache_lock);
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/* Timeout of a tree mount is ultimately determined by its top dentry */
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if (!autofs4_can_expire(top, timeout, do_now))
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return 1;
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return 0;
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}
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static struct dentry *autofs4_check_leaves(struct vfsmount *mnt,
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struct dentry *parent,
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unsigned long timeout,
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int do_now)
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{
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struct dentry *p;
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DPRINTK("parent %p %.*s",
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parent, (int)parent->d_name.len, parent->d_name.name);
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spin_lock(&dcache_lock);
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for (p = parent; p; p = next_dentry(p, parent)) {
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/* Negative dentry - give up */
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if (!simple_positive(p))
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continue;
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DPRINTK("dentry %p %.*s",
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p, (int) p->d_name.len, p->d_name.name);
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p = dget(p);
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spin_unlock(&dcache_lock);
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if (d_mountpoint(p)) {
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/* Can we expire this guy */
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if (!autofs4_can_expire(p, timeout, do_now))
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goto cont;
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/* Can we umount this guy */
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if (!autofs4_mount_busy(mnt, p))
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return p;
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}
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cont:
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dput(p);
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spin_lock(&dcache_lock);
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}
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spin_unlock(&dcache_lock);
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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 *autofs4_expire(struct super_block *sb,
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struct vfsmount *mnt,
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struct autofs_sb_info *sbi,
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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 *expired = NULL;
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struct list_head *next;
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int do_now = how & AUTOFS_EXP_IMMEDIATE;
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int exp_leaves = how & AUTOFS_EXP_LEAVES;
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if ( !sbi->exp_timeout || !root )
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return NULL;
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now = jiffies;
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timeout = sbi->exp_timeout;
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spin_lock(&dcache_lock);
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next = root->d_subdirs.next;
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/* On exit from the loop expire is set to a dgot dentry
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* to expire or it's NULL */
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while ( next != &root->d_subdirs ) {
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struct dentry *dentry = list_entry(next, struct dentry, d_u.d_child);
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/* Negative dentry - give up */
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if (!simple_positive(dentry)) {
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next = next->next;
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continue;
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}
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dentry = dget(dentry);
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spin_unlock(&dcache_lock);
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/* Case 1: indirect mount or top level direct mount */
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if (d_mountpoint(dentry)) {
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DPRINTK("checking mountpoint %p %.*s",
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dentry, (int)dentry->d_name.len, dentry->d_name.name);
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/* Can we expire this guy */
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if (!autofs4_can_expire(dentry, timeout, do_now))
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goto next;
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/* Can we umount this guy */
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if (!autofs4_mount_busy(mnt, dentry)) {
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expired = dentry;
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break;
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}
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goto next;
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}
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if (simple_empty(dentry))
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goto next;
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/* Case 2: tree mount, expire iff entire tree is not busy */
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if (!exp_leaves) {
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/* Lock the tree as we must expire as a whole */
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spin_lock(&sbi->fs_lock);
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if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) {
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struct autofs_info *inf = autofs4_dentry_ino(dentry);
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/* Set this flag early to catch sys_chdir and the like */
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inf->flags |= AUTOFS_INF_EXPIRING;
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spin_unlock(&sbi->fs_lock);
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expired = dentry;
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break;
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}
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spin_unlock(&sbi->fs_lock);
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/* Case 3: direct mount, expire individual leaves */
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} else {
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expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
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if (expired) {
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dput(dentry);
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break;
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}
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}
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next:
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dput(dentry);
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spin_lock(&dcache_lock);
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next = next->next;
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}
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if (expired) {
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DPRINTK("returning %p %.*s",
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expired, (int)expired->d_name.len, expired->d_name.name);
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spin_lock(&dcache_lock);
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list_del(&expired->d_parent->d_subdirs);
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list_add(&expired->d_parent->d_subdirs, &expired->d_u.d_child);
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spin_unlock(&dcache_lock);
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return expired;
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}
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spin_unlock(&dcache_lock);
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return NULL;
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}
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/* Perform an expiry operation */
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int autofs4_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 dentry *dentry;
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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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if ((dentry = autofs4_expire(sb, mnt, sbi, 0)) == NULL)
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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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dput(dentry);
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if ( copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)) )
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return -EFAULT;
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return 0;
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}
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/* Call repeatedly until it returns -EAGAIN, meaning there's nothing
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more to be done */
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int autofs4_expire_multi(struct super_block *sb, struct vfsmount *mnt,
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struct autofs_sb_info *sbi, int __user *arg)
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{
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struct dentry *dentry;
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int ret = -EAGAIN;
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int do_now = 0;
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if (arg && get_user(do_now, arg))
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return -EFAULT;
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if ((dentry = autofs4_expire(sb, mnt, sbi, do_now)) != NULL) {
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struct autofs_info *ino = autofs4_dentry_ino(dentry);
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/* This is synchronous because it makes the daemon a
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little easier */
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ino->flags |= AUTOFS_INF_EXPIRING;
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ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
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ino->flags &= ~AUTOFS_INF_EXPIRING;
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dput(dentry);
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}
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return ret;
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}
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