[PATCH] xfs: don't try to mark uncached buffers stale on error.

[Dave Chinner]

From: Dave Chinner <dchinner at redhat.com>

fsstress failed during a shutdown with the following assert:

XFS: Assertion failed: xfs_buf_islocked(bp), file: fs/xfs/xfs_buf.c, line: 143
.....
 xfs_buf_stale+0x3f/0xf0
 xfs_bioerror_relse+0x2d/0x90
 xfsbdstrat+0x51/0xa0
 xfs_zero_remaining_bytes+0x1d1/0x2d0
 xfs_free_file_space+0x5d0/0x600
 xfs_change_file_space+0x251/0x3a0
 xfs_ioc_space+0xcc/0x130
.....

xfs_zero_remaining_bytes() works with uncached buffers, and hence if
we are preventing IO due to a shutdown, we should not be marking it
stale as that is only for cached buffers. Instead, just mark it with
an error and make sure it gets to the caller.

Signed-off-by: Dave Chinner <dchinner at redhat.com>
---
 fs/xfs/xfs_buf.c | 31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index c06823f..ee85f29 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1125,25 +1125,20 @@ xfs_bioerror_relse(
 	struct xfs_buf	*bp)
 {
 	int64_t		fl = bp->b_flags;
+
 	/*
-	 * No need to wait until the buffer is unpinned.
-	 * We aren't flushing it.
-	 *
-	 * chunkhold expects B_DONE to be set, whether
-	 * we actually finish the I/O or not. We don't want to
-	 * change that interface.
+	 * No need to wait until the buffer is unpinned. We aren't flushing it.
 	 */
 	XFS_BUF_UNREAD(bp);
 	XFS_BUF_DONE(bp);
 	xfs_buf_stale(bp);
 	bp->b_iodone = NULL;
+
+	/*
+	 * There's no reason to mark error for ASYNC buffers as there is no-one
+	 * waiting to collect the error.
+	 */
 	if (!(fl & XBF_ASYNC)) {
-		/*
-		 * Mark b_error and B_ERROR _both_.
-		 * Lot's of chunkcache code assumes that.
-		 * There's no reason to mark error for
-		 * ASYNC buffers.
-		 */
 		xfs_buf_ioerror(bp, EIO);
 		complete(&bp->b_iowait);
 	} else {
@@ -1160,11 +1155,15 @@ xfs_bdstrat_cb(
 	if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
 		trace_xfs_bdstrat_shut(bp, _RET_IP_);
 		/*
-		 * Metadata write that didn't get logged but
-		 * written delayed anyway. These aren't associated
-		 * with a transaction, and can be ignored.
+		 * If this is a cached write, then it is likely to be a delayed
+		 * write metadata buffer that can be ignored because the
+		 * contents are logged. If it's an uncached buffer or a read
+		 * operation, then the caller will get the error through the
+		 * normal IO completion path. We can tell if the buffer is
+		 * cached or not by looking to see if the b_pag field is NULL or
+		 * not.
 		 */
-		if (!bp->b_iodone && !XFS_BUF_ISREAD(bp))
+		if (!bp->b_iodone && !XFS_BUF_ISREAD(bp) && bp->b_pag)
 			return xfs_bioerror_relse(bp);
 		else
 			return xfs_bioerror(bp);
-- 
1.8.3.2