Thanks Mike for fixing.
This was my first attempt to fix something in kernel so I wasn't sure about the patch itself.
- Lukas
On Fri, Jul 29, 2016 at 7:30 PM, Mike Snitzer <snitzer@xxxxxxxxxx> wrote:
On Fri, Jul 29 2016 at 10:35am -0400,
Mike Snitzer <snitzer@xxxxxxxxxx> wrote:
> On Fri, Jul 29 2016 at 10:31am -0400,
> Lukas Herbolt <lherbolt@xxxxxxxxxx> wrote:
>
> > - http://people.redhat.com/~lherbolt/dm-flakey/v4.7-dm_flakey.tar.gz
> >
> > Lukas
>
> Please post an incremental patch relative to 4.7 or latest Linus
> kernel. Don't make people suffer with tarballs of whatever you've
> packaged above.
I pulled out your incremental diff. Your proposed fix isn't correct. It
breaks the corrupt_bio_byte feature. We cannot blindly drop reads early
in flakey_map(), like you've proposed, because the corrupt_bio_byte
feature relies on corrupt data being returned on read during the
down_interval.
The issue reported is: reads aren't dropped during the "down_interval".
I do agree that this needs fixing, and it was commit a3998799fb4df ("dm
flakey: add corrupt_bio_byte feature") that caused this regression.
But a fix must not break the corrupt_bio_byte feature.
This fix should resolve the problem, I'll be staging it to go upstream
during the 4.8-rc cycle (Akira, please test to verify your test fails as
expected now):
From: Mike Snitzer <snitzer@xxxxxxxxxx>
Date: Fri, 29 Jul 2016 13:19:55 -0400
Subject: [PATCH] dm flakey: error READ bios during the down_interval
When the corrupt_bio_byte feature was introduced it caused READ bios to
no longer be errored with -EIO during the down_interval. This had to do
with the complexity of needing to submit READs if the corrupt_bio_byte
feature was used.
Fix it so READ bios are properly errored with -EIO; doing so early in
flakey_map() as long as there isn't a match for the corrupt_bio_byte
feature.
Fixes: a3998799fb4df ("dm flakey: add corrupt_bio_byte feature")
Reported-by: Akira Hayakawa <ruby.wktk@xxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
drivers/md/dm-flakey.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)
diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c
index 29b99fb..19db13e 100644
--- a/drivers/md/dm-flakey.c
+++ b/drivers/md/dm-flakey.c
@@ -289,10 +289,16 @@ static int flakey_map(struct dm_target *ti, struct bio *bio)
pb->bio_submitted = true;
/*
- * Map reads as normal.
+ * Map reads as normal only if corrupt_bio_byte set.
*/
- if (bio_data_dir(bio) == READ)
- goto map_bio;
+ if (bio_data_dir(bio) == READ) {
+ /* If flags were specified, only corrupt those that match. */
+ if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == READ) &&
+ all_corrupt_bio_flags_match(bio, fc))
+ goto map_bio;
+ else
+ return -EIO;
+ }
/*
* Drop writes?
@@ -330,12 +336,13 @@ static int flakey_end_io(struct dm_target *ti, struct bio *bio, int error)
/*
* Corrupt successful READs while in down state.
- * If flags were specified, only corrupt those that match.
*/
- if (fc->corrupt_bio_byte && !error && pb->bio_submitted &&
- (bio_data_dir(bio) == READ) && (fc->corrupt_bio_rw == READ) &&
- all_corrupt_bio_flags_match(bio, fc))
- corrupt_bio_data(bio, fc);
+ if (!error && pb->bio_submitted && (bio_data_dir(bio) == READ)) {
+ if (fc->corrupt_bio_byte)
+ corrupt_bio_data(bio, fc);
+ else
+ return -EIO;
+ }
return error;
}
--
2.7.4 (Apple Git-66)
Lukas Herbolt
RHCE, RH436, BSc, SSc
Senior Technical Support Engineer
Global Support Services (GSS)
Email: lherbolt@xxxxxxxxxx
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