ocfs2_dlm: Fixes race between migrate and dirty

dlmthread was removing lockres' from the dirty list
and resetting the dirty flag before shuffling the list.
This patch retains the dirty state flag until the lists
are shuffled.

Signed-off-by: Kurt Hackel <kurt.hackel@oracle.com>
Signed-off-by: Sunil Mushran <Sunil.Mushran@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

1 files changed, 15 insertions, 1 deletions

diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
index 251c48028ea3..a65a87726d6a 100644
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -2707,8 +2707,15 @@ static int dlm_mark_lockres_migrating(struct dlm_ctxt *dlm,
 	__dlm_lockres_reserve_ast(res);
 	spin_unlock(&res->spinlock);
 
-	/* now flush all the pending asts.. hang out for a bit */
+	/* now flush all the pending asts */
 	dlm_kick_thread(dlm, res);
+	/* before waiting on DIRTY, block processes which may
+	 * try to dirty the lockres before MIGRATING is set */
+	spin_lock(&res->spinlock);
+	BUG_ON(res->state & DLM_LOCK_RES_BLOCK_DIRTY);
+	res->state |= DLM_LOCK_RES_BLOCK_DIRTY;
+	spin_unlock(&res->spinlock);
+	/* now wait on any pending asts and the DIRTY state */
 	wait_event(dlm->ast_wq, !dlm_lockres_is_dirty(dlm, res));
 	dlm_lockres_release_ast(dlm, res);
 
@@ -2734,6 +2741,13 @@ again:
 		mlog(0, "trying again...\n");
 		goto again;
 	}
+	/* now that we are sure the MIGRATING state is there, drop
+	 * the unneded state which blocked threads trying to DIRTY */
+	spin_lock(&res->spinlock);
+	BUG_ON(!(res->state & DLM_LOCK_RES_BLOCK_DIRTY));
+	BUG_ON(!(res->state & DLM_LOCK_RES_MIGRATING));
+	res->state &= ~DLM_LOCK_RES_BLOCK_DIRTY;
+	spin_unlock(&res->spinlock);
 
 	/* did the target go down or die? */
 	spin_lock(&dlm->spinlock);