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-rw-r--r--fs/ocfs2/dlmglue.c19
1 files changed, 18 insertions, 1 deletions
diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
index ebc4a49801b..9e8ed607173 100644
--- a/fs/ocfs2/dlmglue.c
+++ b/fs/ocfs2/dlmglue.c
@@ -119,6 +119,18 @@ struct ocfs2_lock_res_ops {
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);