[PATCH] autofs4: NFY_NONE wait race fix

This patch fixes two problems.

First, the comparison of entries in the waitq.c was incorrect.

Second, the NFY_NONE check was incorrect. The test of whether the dentry
is mounted if ineffective, for example, if an expire fails then we could
wait forever on a non existant expire. The bug was identified by Jeff
Moyer.

The patch changes autofs4 to wait on expires only as this is all that's
needed.  If there is no existing wait when autofs4_wait is call with a type
of NFY_NONE it delays until either a wait appears or the the expire flag is
cleared.

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, 3 insertions, 7 deletions

diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 84e030c8ddd0..5100f984783f 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -327,6 +327,7 @@ static int try_to_fill_dentry(struct dentry *dentry, int flags)
 static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
+        struct autofs_info *ino = autofs4_dentry_ino(dentry);
         int oz_mode = autofs4_oz_mode(sbi);
         unsigned int lookup_type;
         int status;
@@ -340,13 +341,8 @@ static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
         if (oz_mode || !lookup_type)
                 goto done;
 
-        /*
-         * If a request is pending wait for it.
-         * If it's a mount then it won't be expired till at least
-         * a liitle later and if it's an expire then we might need
-         * to mount it again.
-         */
-        if (autofs4_ispending(dentry)) {
+        /* If an expire request is pending wait for it. */
+        if (ino && (ino->flags & AUTOFS_INF_EXPIRING)) {
                 DPRINTK("waiting for active request %p name=%.*s",
                         dentry, dentry->d_name.len, dentry->d_name.name);