Commit 3a9720ce authored by Ian Kent's avatar Ian Kent Committed by Linus Torvalds
Browse files

[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: default avatarIan Kent <raven@themaw.net>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 4dcd00b1

fs/autofs4/autofs_i.h

+12 −2
Original line number Diff line number Diff line
@@ -102,6 +102,7 @@ struct autofs_sb_info { 
	int needs_reghost;

	struct super_block *sb;

	struct semaphore wq_sem;

	spinlock_t fs_lock;

	struct autofs_wait_queue *queues; /* Wait queue pointer */

};
@@ -127,9 +128,18 @@ static inline int autofs4_oz_mode(struct autofs_sb_info *sbi) { 
static inline int autofs4_ispending(struct dentry *dentry)

{

	struct autofs_info *inf = autofs4_dentry_ino(dentry);

	int pending = 0;



	return (dentry->d_flags & DCACHE_AUTOFS_PENDING) ||

		(inf != NULL && inf->flags & AUTOFS_INF_EXPIRING);

	if (dentry->d_flags & DCACHE_AUTOFS_PENDING)

		return 1;



	if (inf) {

		spin_lock(&inf->sbi->fs_lock);

		pending = inf->flags & AUTOFS_INF_EXPIRING;

		spin_unlock(&inf->sbi->fs_lock);

	}



	return pending;

}



static inline void autofs4_copy_atime(struct file *src, struct file *dst)

fs/autofs4/expire.c

+14 −2
Original line number Diff line number Diff line
@@ -99,6 +99,10 @@ static int autofs4_check_tree(struct vfsmount *mnt, 
	if (!autofs4_can_expire(top, timeout, do_now))

		return 0;



	/* Is someone visiting anywhere in the tree ? */

	if (may_umount_tree(mnt))

		return 0;



	spin_lock(&dcache_lock);

repeat:

	next = this_parent->d_subdirs.next;
@@ -270,10 +274,18 @@ static struct dentry *autofs4_expire(struct super_block *sb, 


		/* Case 2: tree mount, expire iff entire tree is not busy */

		if (!exp_leaves) {

			/* Lock the tree as we must expire as a whole */

			spin_lock(&sbi->fs_lock);

			if (autofs4_check_tree(mnt, dentry, timeout, do_now)) {

				struct autofs_info *inf = autofs4_dentry_ino(dentry);



				/* Set this flag early to catch sys_chdir and the like */

				inf->flags |= AUTOFS_INF_EXPIRING;

				spin_unlock(&sbi->fs_lock);

				expired = dentry;

				break;

			}

			spin_unlock(&sbi->fs_lock);

		/* Case 3: direct mount, expire individual leaves */

		} else {

			expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);

fs/autofs4/inode.c

+1 −0
Original line number Diff line number Diff line
@@ -206,6 +206,7 @@ int autofs4_fill_super(struct super_block *s, void *data, int silent) 
	sbi->version = 0;

	sbi->sub_version = 0;

	init_MUTEX(&sbi->wq_sem);

	spin_lock_init(&sbi->fs_lock);

	sbi->queues = NULL;

	s->s_blocksize = 1024;

	s->s_blocksize_bits = 10;

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