[PATCH] autofs4: tree race fix
For tree mount maps, a call to chdir or chroot, to a directory above the moint point directories at a certain time during the expire results in the expire incorrectly thinking the tree is not busy. This patch adds a check to see if the filesystem above the tree mount points is busy and also locks the filesystem during the tree mount expire to prevent the race. Signed-off-by: Ian Kent <raven@themaw.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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@ -102,6 +102,7 @@ struct autofs_sb_info {
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int needs_reghost;
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struct super_block *sb;
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struct semaphore wq_sem;
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spinlock_t fs_lock;
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struct autofs_wait_queue *queues; /* Wait queue pointer */
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};
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@ -127,9 +128,18 @@ static inline int autofs4_oz_mode(struct autofs_sb_info *sbi) {
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static inline int autofs4_ispending(struct dentry *dentry)
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{
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struct autofs_info *inf = autofs4_dentry_ino(dentry);
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int pending = 0;
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return (dentry->d_flags & DCACHE_AUTOFS_PENDING) ||
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(inf != NULL && inf->flags & AUTOFS_INF_EXPIRING);
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if (dentry->d_flags & DCACHE_AUTOFS_PENDING)
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return 1;
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if (inf) {
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spin_lock(&inf->sbi->fs_lock);
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pending = inf->flags & AUTOFS_INF_EXPIRING;
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spin_unlock(&inf->sbi->fs_lock);
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}
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return pending;
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}
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static inline void autofs4_copy_atime(struct file *src, struct file *dst)
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@ -99,6 +99,10 @@ static int autofs4_check_tree(struct vfsmount *mnt,
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if (!autofs4_can_expire(top, timeout, do_now))
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return 0;
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/* Is someone visiting anywhere in the tree ? */
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if (may_umount_tree(mnt))
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return 0;
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spin_lock(&dcache_lock);
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repeat:
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next = this_parent->d_subdirs.next;
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@ -270,10 +274,18 @@ static struct dentry *autofs4_expire(struct super_block *sb,
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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_check_tree(mnt, dentry, timeout, do_now)) {
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expired = dentry;
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break;
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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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@ -206,6 +206,7 @@ int autofs4_fill_super(struct super_block *s, void *data, int silent)
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sbi->version = 0;
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sbi->sub_version = 0;
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init_MUTEX(&sbi->wq_sem);
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spin_lock_init(&sbi->fs_lock);
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sbi->queues = NULL;
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s->s_blocksize = 1024;
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s->s_blocksize_bits = 10;
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