ocfs2: Add ->check_downconvert callback in dlmglue

This will allow lock types to force a requeue of a lock downconvert.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
index ebc4a49801bdb4326ef25d42b1aefea73448af8a..9e8ed607173bc5849956a4df137df0e15005991a 100644 (file)
--- a/fs/ocfs2/dlmglue.c
+++ b/fs/ocfs2/dlmglue.c
@@ -118,6 +118,18 @@ struct ocfs2_lock_res_ops {
        int  (*unblock)(struct ocfs2_lock_res *, struct ocfs2_unblock_ctl *);
        void (*post_unlock)(struct ocfs2_super *, struct ocfs2_lock_res *);
 
+       /*
+        * Allow a lock type to add checks to determine whether it is
+        * safe to downconvert a lock. Return 0 to re-queue the
+        * downconvert at a later time, nonzero to continue.
+        *
+        * For most locks, the default checks that there are no
+        * incompatible holders are sufficient.
+        *
+        * Called with the lockres spinlock held.
+        */
+       int (*check_downconvert)(struct ocfs2_lock_res *, int);
+
        /*
         * LOCK_TYPE_* flags which describe the specific requirements
         * of a lock type. Descriptions of each individual flag follow.
@@ -2657,6 +2669,12 @@ recheck:
            && (lockres->l_flags & OCFS2_LOCK_REFRESHING))
                goto leave_requeue;
 
+       new_level = ocfs2_highest_compat_lock_level(lockres->l_blocking);
+
+       if (lockres->l_ops->check_downconvert
+           && !lockres->l_ops->check_downconvert(lockres, new_level))
+               goto leave_requeue;
+
        /* If we get here, then we know that there are no more
         * incompatible holders (and anyone asking for an incompatible
         * lock is blocked). We can now downconvert the lock */
@@ -2684,7 +2702,6 @@ recheck:
 
 downconvert:
        ctl->requeue = 0;
-       new_level = ocfs2_highest_compat_lock_level(lockres->l_blocking);
 
        ocfs2_prepare_downconvert(lockres, new_level);
        spin_unlock_irqrestore(&lockres->l_lock, flags);