On Thu, Jun 14 2018 at 2:12P -0400, Mike Snitzer <[email protected]> wrote:
> On Thu, Jun 14 2018 at 4:19am -0400, > Christoph Hellwig <[email protected]> wrote: > > > Hi Neil, > > > > In commit 18a25da8 ("dm: ensure bio submission follows a depth-first > > tree walk") you've added a call to bio_clone_bioset to > > __split_and_process_bio. Unlike all other bio splitting code this > > actually allocates a new bio_vec array instead of just splitting the bio > > and the iterator. I can't actually find a good reason for that either > > in a cursory review of the code, the commit or the comments. > > > > Do you remember why this can't just use bio_clone_fast? > > Your question caused me to revisit this code and it is suspect for a > couple reasons: > > 1) I'm also not seeing why we need bio_clone_bioset() The patch below seems to work fine (given quick testing).. It also has a side-effect of not breaking integrity support (which commit 18a25da8 appears to do because it isn't accounting for any of the integrity stuff bio_split, or dm.c:clone_bio, does). FYI, my other concerns in my my previous reply were unfounded and due to misreading the existing code. Neil, please still feel free to have a look at this to see if you can recall why you used bio_clone_bioset(). If in the end you agree that the following patch is fine please let me know and I'll get a proper fix staged. Thanks, Mike diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 20a8d63..dfb4783 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1582,10 +1582,9 @@ static blk_qc_t __split_and_process_bio(struct mapped_device *md, * the usage of io->orig_bio in dm_remap_zone_report() * won't be affected by this reassignment. */ - struct bio *b = bio_clone_bioset(bio, GFP_NOIO, - &md->queue->bio_split); + struct bio *b = bio_split(bio, bio_sectors(bio) - ci.sector_count, + GFP_NOIO, &md->queue->bio_split); ci.io->orig_bio = b; - bio_advance(bio, (bio_sectors(bio) - ci.sector_count) << 9); bio_chain(b, bio); ret = generic_make_request(bio); break; -- dm-devel mailing list [email protected] https://www.redhat.com/mailman/listinfo/dm-devel
