[PATCH for v4.3-rc] dm: fix request-based dm error reporting

[PATCH for v4.3-rc] dm: fix request-based dm error reporting

[Junichi Nomura]

end_clone_bio() is a endio callback for clone bio and should check
and save the clone's bi_error for error reporting.  However,
4246a0b63bd8 ("block: add a bi_error field to struct bio") changed
the function to check the original bio's bi_error, which is 0.

Without this fix, clone's error is ignored and reported to the
original request as success.  Thus data corruption will be observed.

Fixes: 4246a0b63bd8 ("block: add a bi_error field to struct bio")
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: Christoph Hellwig <hch@lst.de>
---
 drivers/md/dm.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 7289ece..dd6e667 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1001,7 +1001,9 @@ static void end_clone_bio(struct bio *clone)
 	struct dm_rq_target_io *tio = info->tio;
 	struct bio *bio = info->orig;
 	unsigned int nr_bytes = info->orig->bi_iter.bi_size;
+	int error;
 
+	error = clone->bi_error;
 	bio_put(clone);
 
 	if (tio->error)
@@ -1011,13 +1013,13 @@ static void end_clone_bio(struct bio *clone)
 		 * the remainder.
 		 */
 		return;
-	else if (bio->bi_error) {
+	else if (error) {
 		/*
 		 * Don't notice the error to the upper layer yet.
 		 * The error handling decision is made by the target driver,
 		 * when the request is completed.
 		 */
-		tio->error = bio->bi_error;
+		tio->error = error;
 		return;
 	}
 
-- 
2.1.0

Re: [PATCH for v4.3-rc] dm: fix request-based dm error reporting

[Mike Snitzer]

On Tue, Oct 06 2015 at 12:19am -0400,
Junichi Nomura <j-nomura@ce.jp.nec.com> wrote:

> end_clone_bio() is a endio callback for clone bio and should check
> and save the clone's bi_error for error reporting.  However,
> 4246a0b63bd8 ("block: add a bi_error field to struct bio") changed
> the function to check the original bio's bi_error, which is 0.
> 
> Without this fix, clone's error is ignored and reported to the
> original request as success.  Thus data corruption will be observed.
> 
> Fixes: 4246a0b63bd8 ("block: add a bi_error field to struct bio")
> Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
> Cc: Christoph Hellwig <hch@lst.de>

Thanks, I've applied it here:
https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=for-next&id=50887bd139b83ce4489ed865a04bf1be5559c4ad

I'll send it to Linus by the end of the week for 4.3-rc5 inclusion.