[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>
diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index 31540a6..500425e 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -99,6 +99,10 @@
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 @@
/* 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)) {
- expired = dentry;
- break;
+ 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);