[PATCH 13/19] ocfs2: check for a metadata write error with buffer_write_io_error()

[Chao Shi <coshi036@gmail.com>]

ocfs2_write_block() and ocfs2_write_super_or_backup() detect a failed write
by looking at BH_Uptodate afterwards.  That relies on the write completion
handler clearing BH_Uptodate on error, which this series removes: a buffer
whose write failed still holds the data the filesystem asked to be written,
so declaring it not up to date is wrong and makes callers re-read it.

Test BH_Write_EIO instead.  Note that ocfs2_write_block()'s test is the
positive one, so the sense has to be inverted rather than the flag simply
swapped.

The comment in ocfs2_write_block()'s error arm needs updating for the same
reason.  It said the clustered uptodate information did not have to be
removed because the buffer was not marked locally uptodate; after this
series it is, so the reason no longer holds.  Not advertising the block to
the cluster is still the right thing to do - the data is in memory but not
on disk - so only the justification changes, not the behaviour.

No behaviour change today - a failed write sets BH_Write_EIO and clears
BH_Uptodate together.  It stops being a no-op at the end of the series,
where the new test is the one that still works.

Signed-off-by: Chao Shi <coshi036@gmail.com>
---
 fs/ocfs2/buffer_head_io.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/fs/ocfs2/buffer_head_io.c b/fs/ocfs2/buffer_head_io.c
index 7bfe377af2df..733ceda79ca1 100644
--- a/fs/ocfs2/buffer_head_io.c
+++ b/fs/ocfs2/buffer_head_io.c
@@ -66,12 +66,14 @@ int ocfs2_write_block(struct ocfs2_super *osb, struct buffer_head *bh,
 
 	wait_on_buffer(bh);
 
-	if (buffer_uptodate(bh)) {
+	if (!buffer_write_io_error(bh)) {
 		ocfs2_set_buffer_uptodate(ci, bh);
 	} else {
-		/* We don't need to remove the clustered uptodate
-		 * information for this bh as it's not marked locally
-		 * uptodate. */
+		/*
+		 * The buffer still holds what we tried to write, but it did
+		 * not reach the disk, so don't advertise it to the cluster
+		 * as up to date.
+		 */
 		ret = -EIO;
 		mlog_errno(ret);
 	}
@@ -446,7 +448,7 @@ int ocfs2_write_super_or_backup(struct ocfs2_super *osb,
 
 	wait_on_buffer(bh);
 
-	if (!buffer_uptodate(bh)) {
+	if (buffer_write_io_error(bh)) {
 		ret = -EIO;
 		mlog_errno(ret);
 	}
-- 
2.43.0