xfs: factor out buffer I/O failure code

We use the same buffer I/O failure code in a few different places.
It's not much code, but it's not necessarily self-explanatory.
Factor it into a helper and document it in one place.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Allison Collins <allison.henderson@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_buf.c

@@ -1248,6 +1248,22 @@ xfs_buf_ioerror_alert(
 			-bp->b_error);
 }
 
+/*
+ * To simulate an I/O failure, the buffer must be locked and held with at least
+ * three references. The LRU reference is dropped by the stale call. The buf
+ * item reference is dropped via ioend processing. The third reference is owned
+ * by the caller and is dropped on I/O completion if the buffer is XBF_ASYNC.
+ */
+void
+xfs_buf_ioend_fail(
+	struct xfs_buf	*bp)
+{
+	bp->b_flags &= ~XBF_DONE;
+	xfs_buf_stale(bp);
+	xfs_buf_ioerror(bp, -EIO);
+	xfs_buf_ioend(bp);
+}
+
 int
 xfs_bwrite(
 	struct xfs_buf		*bp)
@@ -1480,10 +1496,7 @@ __xfs_buf_submit(
 
 	/* on shutdown we stale and complete the buffer immediately */
 	if (XFS_FORCED_SHUTDOWN(bp->b_mount)) {
-		xfs_buf_ioerror(bp, -EIO);
-		bp->b_flags &= ~XBF_DONE;
-		xfs_buf_stale(bp);
-		xfs_buf_ioend(bp);
+		xfs_buf_ioend_fail(bp);
 		return -EIO;
 	}
 

fs/xfs/xfs_buf.h

@@ -263,6 +263,7 @@ extern void __xfs_buf_ioerror(struct xfs_buf *bp, int error,
 		xfs_failaddr_t failaddr);
 #define xfs_buf_ioerror(bp, err) __xfs_buf_ioerror((bp), (err), __this_address)
 extern void xfs_buf_ioerror_alert(struct xfs_buf *bp, xfs_failaddr_t fa);
+void xfs_buf_ioend_fail(struct xfs_buf *);
 
 extern int __xfs_buf_submit(struct xfs_buf *bp, bool);
 static inline int xfs_buf_submit(struct xfs_buf *bp)

fs/xfs/xfs_buf_item.c

@@ -471,28 +471,13 @@ xfs_buf_item_unpin(
 		xfs_buf_relse(bp);
 	} else if (freed && remove) {
 		/*
-		 * There are currently two references to the buffer - the active
-		 * LRU reference and the buf log item. What we are about to do
-		 * here - simulate a failed IO completion - requires 3
-		 * references.
-		 *
-		 * The LRU reference is removed by the xfs_buf_stale() call. The
-		 * buf item reference is removed by the xfs_buf_iodone()
-		 * callback that is run by xfs_buf_do_callbacks() during ioend
-		 * processing (via the bp->b_iodone callback), and then finally
-		 * the ioend processing will drop the IO reference if the buffer
-		 * is marked XBF_ASYNC.
-		 *
-		 * Hence we need to take an additional reference here so that IO
-		 * completion processing doesn't free the buffer prematurely.
+		 * The buffer must be locked and held by the caller to simulate
+		 * an async I/O failure.
 		 */
 		xfs_buf_lock(bp);
 		xfs_buf_hold(bp);
 		bp->b_flags |= XBF_ASYNC;
-		xfs_buf_ioerror(bp, -EIO);
-		bp->b_flags &= ~XBF_DONE;
-		xfs_buf_stale(bp);
-		xfs_buf_ioend(bp);
+		xfs_buf_ioend_fail(bp);
 	}
 }
 

fs/xfs/xfs_inode.c

@@ -3630,11 +3630,7 @@ xfs_iflush_cluster(
 	 */
 	ASSERT(bp->b_iodone);
 	bp->b_flags |= XBF_ASYNC;
-	bp->b_flags &= ~XBF_DONE;
-	xfs_buf_stale(bp);
-	xfs_buf_ioerror(bp, -EIO);
-	xfs_buf_ioend(bp);
-
+	xfs_buf_ioend_fail(bp);
 	xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
 
 	/* abort the corrupt inode, as it was not attached to the buffer */