xfs: simplify the xfs_buf_ioend_disposition calling convention

Now that all the actual error handling is in a single place,
xfs_buf_ioend_disposition just needs to return true if took ownership of
the buffer, or false if not instead of the tristate.  Also move the
error check back in the caller to optimize for the fast path, and give
the function a better fitting name.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_buf.c

@@ -1223,29 +1223,17 @@ xfs_buf_ioerror_permanent(
  * If we get repeated async write failures, then we take action according to the
  * error configuration we have been set up to use.
  *
- * Multi-state return value:
- *
- * XBF_IOEND_FINISH: run callback completions
- * XBF_IOEND_DONE: resubmitted immediately, do not run any completions
- * XBF_IOEND_FAIL: transient error, run failure callback completions and then
- *    release the buffer
- */
-enum xfs_buf_ioend_disposition {
-	XBF_IOEND_FINISH,
-	XBF_IOEND_DONE,
-	XBF_IOEND_FAIL,
-};
-
-static enum xfs_buf_ioend_disposition
-xfs_buf_ioend_disposition(
+ * Returns true if this function took care of error handling and the caller must
+ * not touch the buffer again.  Return false if the caller should proceed with
+ * normal I/O completion handling.
+ */
+static bool
+xfs_buf_ioend_handle_error(
 	struct xfs_buf		*bp)
 {
 	struct xfs_mount	*mp = bp->b_mount;
 	struct xfs_error_cfg	*cfg;
 
-	if (likely(!bp->b_error))
-		return XBF_IOEND_FINISH;
-
 	/*
 	 * If we've already decided to shutdown the filesystem because of I/O
 	 * errors, there's no point in giving this a retry.
@@ -1291,18 +1279,18 @@ xfs_buf_ioend_disposition(
 		ASSERT(list_empty(&bp->b_li_list));
 	xfs_buf_ioerror(bp, 0);
 	xfs_buf_relse(bp);
-	return XBF_IOEND_FAIL;
+	return true;
 
 resubmit:
 	xfs_buf_ioerror(bp, 0);
 	bp->b_flags |= (XBF_WRITE | XBF_DONE | XBF_WRITE_FAIL);
 	xfs_buf_submit(bp);
-	return XBF_IOEND_DONE;
+	return true;
 out_stale:
 	xfs_buf_stale(bp);
 	bp->b_flags |= XBF_DONE;
 	trace_xfs_buf_error_relse(bp, _RET_IP_);
-	return XBF_IOEND_FINISH;
+	return false;
 }
 
 static void
@@ -1340,14 +1328,8 @@ xfs_buf_ioend(
 			bp->b_flags |= XBF_DONE;
 		}
 
-		switch (xfs_buf_ioend_disposition(bp)) {
-		case XBF_IOEND_DONE:
+		if (unlikely(bp->b_error) && xfs_buf_ioend_handle_error(bp))
 			return;
-		case XBF_IOEND_FAIL:
-			return;
-		default:
-			break;
-		}
 
 		/* clear the retry state */
 		bp->b_last_error = 0;