Subject: Re: linux-next: build failure after merge of the device-mapper tree

From: Mike Snitzer <[email-masked]>
Date: Mon, 4 Nov 2013 22:20:54 -0500

On Mon, Nov 04 2013 at  9:51pm -0500,
Stephen Rothwell <[email-masked]> wrote:

> Hi all,
> 
> After merging the device-mapper tree, today's linux-next build (x86_64
> allmodconfig) failed like this:
> 
> drivers/md/dm-cache-target.c: In function 'bio_writes_complete_block':
> drivers/md/dm-cache-target.c:1020:7: error: 'struct bio' has no member named 'bi_size'
>    (bio->bi_size == (cache->sectors_per_block << SECTOR_SHIFT));
>        ^
> 
> Caused by commit 1bd270d800ec ("dm cache: promotion optimisation for
> writes") interacting with commit ed2d2f9a8265 ("block: Abstract out bvec
> iterator") from the block tree.
> 
> I applied this fix up patch and can carry it as necessary:

Hi Stephen,

Yes that is needed, as is this (which begs the question: how should I be
handling the fact that post-merge changes are needed?  Especially since
Linus will need the changes too):

 drivers/md/dm-cache-target.c |   12 ++++++------
 1 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index a977d5c..52d7d75 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -85,6 +85,12 @@ static void dm_unhook_bio(struct dm_hook_info *h, struct bio *bio)
 {
 	bio->bi_end_io = h->bi_end_io;
 	bio->bi_private = h->bi_private;
+
+	/*
+	 * Must bump bi_remaining to allow bio to complete with
+	 * restored bi_end_io.
+	 */
+	atomic_inc(&bio->bi_remaining);
 }
 
 /*----------------------------------------------------------------*/
@@ -746,12 +752,6 @@ static void writethrough_endio(struct bio *bio, int err)
 
 	dm_unhook_bio(&pb->hook_info, bio);
 
-	/*
-	 * Must bump bi_remaining to allow bio to complete with
-	 * restored bi_end_io.
-	 */
-	atomic_inc(&bio->bi_remaining);
-
 	if (err) {
 		bio_endio(bio, err);
 		return;