[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>

1 files changed, 12 insertions, 2 deletions

diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
index 978987735252..c7b2b8890188 100644
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -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)