1 files changed, 21 insertions, 16 deletions

diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
index 1cb087b320b1..464587c5a2cb 100644
--- a/fs/xfs/xfs_buf_item.c
+++ b/fs/xfs/xfs_buf_item.c
@@ -474,17 +474,8 @@ xfs_buf_item_pin(
 }
 
 /*
- * This is called to unpin the buffer associated with the buf log
- * item which was previously pinned with a call to xfs_buf_item_pin().
- *
- * Also drop the reference to the buf item for the current transaction.
- * If the XFS_BLI_STALE flag is set and we are the last reference,
- * then free up the buf log item and unlock the buffer.
- *
- * If the remove flag is set we are called from uncommit in the
- * forced-shutdown path.  If that is true and the reference count on
- * the log item is going to drop to zero we need to free the item's
- * descriptor in the transaction.
+ * This is called to unpin the buffer associated with the buf log item which
+ * was previously pinned with a call to xfs_buf_item_pin().
  */
 STATIC void
 xfs_buf_item_unpin(
@@ -501,12 +492,26 @@ xfs_buf_item_unpin(
 
 	trace_xfs_buf_item_unpin(bip);
 
+	/*
+	 * Drop the bli ref associated with the pin and grab the hold required
+	 * for the I/O simulation failure in the abort case. We have to do this
+	 * before the pin count drops because the AIL doesn't acquire a bli
+	 * reference. Therefore if the refcount drops to zero, the bli could
+	 * still be AIL resident and the buffer submitted for I/O (and freed on
+	 * completion) at any point before we return. This can be removed once
+	 * the AIL properly holds a reference on the bli.
+	 */
 	freed = atomic_dec_and_test(&bip->bli_refcount);
-
+	if (freed && !stale && remove)
+		xfs_buf_hold(bp);
 	if (atomic_dec_and_test(&bp->b_pin_count))
 		wake_up_all(&bp->b_waiters);
 
-	if (freed && stale) {
+	 /* nothing to do but drop the pin count if the bli is active */
+	if (!freed)
+		return;
+
+	if (stale) {
 		ASSERT(bip->bli_flags & XFS_BLI_STALE);
 		ASSERT(xfs_buf_islocked(bp));
 		ASSERT(bp->b_flags & XBF_STALE);
@@ -549,13 +554,13 @@ xfs_buf_item_unpin(
 			ASSERT(bp->b_log_item == NULL);
 		}
 		xfs_buf_relse(bp);
-	} else if (freed && remove) {
+	} else if (remove) {
 		/*
 		 * The buffer must be locked and held by the caller to simulate
-		 * an async I/O failure.
+		 * an async I/O failure. We acquired the hold for this case
+		 * before the buffer was unpinned.
 		 */
 		xfs_buf_lock(bp);
-		xfs_buf_hold(bp);
 		bp->b_flags |= XBF_ASYNC;
 		xfs_buf_ioend_fail(bp);
 	}