[PATCH 6/7] autofs - dont hold spin lock over direct mount expire

[Ian Kent]

From: Ian Kent <ik...@redhat.com>

Commit 7cbdb4a286 altered the autofs indirect mount expire to
not hold a spin lock during the expire check.

The direct mount expire needs the same treatment because to
make autofs expires namespace aware may_umount_tree() needs to
to use a similar method to may_umount() when checking if a mount
tree is in use.

This means may_umount_tree() will end up taking the namespace_sem
for the check so the autofs direct mount expire won't be allowed
to hold a spin lock over the check.

Signed-off-by: Ian Kent <ra...@themaw.net>
Cc: Al Viro <v...@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebied...@xmission.com>
Cc: Omar Sandoval <osan...@osandov.com>
---
 fs/autofs4/expire.c |   17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index 13178bf..57725d4 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -310,26 +310,29 @@ struct dentry *autofs4_expire_direct(struct super_block 
*sb,
        now = jiffies;
        timeout = sbi->exp_timeout;
 
-       spin_lock(&sbi->fs_lock);
-       ino = autofs4_dentry_ino(root);
-       /* No point expiring a pending mount */
-       if (ino->flags & AUTOFS_INF_PENDING)
-               goto out;
        if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
+               spin_lock(&sbi->fs_lock);
+               ino = autofs4_dentry_ino(root);
+               /* No point expiring a pending mount */
+               if (ino->flags & AUTOFS_INF_PENDING) {
+                       spin_unlock(&sbi->fs_lock);
+                       goto out;
+               }
                ino->flags |= AUTOFS_INF_WANT_EXPIRE;
                spin_unlock(&sbi->fs_lock);
                synchronize_rcu();
-               spin_lock(&sbi->fs_lock);
                if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
+                       spin_lock(&sbi->fs_lock);
                        ino->flags |= AUTOFS_INF_EXPIRING;
                        init_completion(&ino->expire_complete);
                        spin_unlock(&sbi->fs_lock);
                        return root;
                }
+               spin_lock(&sbi->fs_lock);
                ino->flags &= ~AUTOFS_INF_WANT_EXPIRE;
+               spin_unlock(&sbi->fs_lock);
        }
 out:
-       spin_unlock(&sbi->fs_lock);
        dput(root);
 
        return NULL;