On Mon, Apr 11 2022 at 12:58P -0400, Mike Snitzer <[email protected]> wrote:
> On Sat, Apr 09 2022 at 1:15P -0400, > Christoph Hellwig <[email protected]> wrote: > > > On Fri, Apr 08, 2022 at 11:42:51AM -0400, Mike Snitzer wrote: > > > I think we can achieve the goal of efficient cloning/remapping for > > > both usecases simply by splitting out the bio_set_dev() and leaving it > > > to the caller to pick which interface to use (e.g. clone vs > > > clone_and_remap). > > > > You can just pass a NULL bdev to bio_alloc_clone/bio_init_clone. > > I've been hoping to get rid of that, but if we have a clear use case > > it will have to stay. > > DM core is just using bio_alloc_clone. And bio_alloc_bioset() allows > bdev to be NULL -- so you're likely referring to that (which will skip > bio_init's bio_associate_blkg). ... > diff --git a/block/bio.c b/block/bio.c > index 7892f1108ca6..0340acc283a0 100644 > --- a/block/bio.c > +++ b/block/bio.c > @@ -772,14 +772,16 @@ static int __bio_clone(struct bio *bio, struct bio > *bio_src, gfp_t gfp) > bio_set_flag(bio, BIO_CLONED); > if (bio_flagged(bio_src, BIO_THROTTLED)) > bio_set_flag(bio, BIO_THROTTLED); > - if (bio->bi_bdev == bio_src->bi_bdev && > - bio_flagged(bio_src, BIO_REMAPPED)) > - bio_set_flag(bio, BIO_REMAPPED); > bio->bi_ioprio = bio_src->bi_ioprio; > bio->bi_iter = bio_src->bi_iter; > > - bio_clone_blkg_association(bio, bio_src); > - blkcg_bio_issue_init(bio); > + if (bio->bi_bdev == bio_src->bi_bdev) { > + if (bio_flagged(bio_src, BIO_REMAPPED)) > + bio_set_flag(bio, BIO_REMAPPED); > + > + bio_clone_blkg_association(bio, bio_src); > + blkcg_bio_issue_init(bio); > + } > > if (bio_crypt_clone(bio, bio_src, gfp) < 0) > return -ENOMEM; > > Think this will fix some of the performance penalty of redundant blkcg > initialization that I reported (though like was also discussed: more > work likely needed to further optimize bio_associate_blkg). Looking closer at the case where bio_{alloc,init}_clone are passed a bdev, bio_init() will call bio_associate_blkg() so the __bio_clone() work to do anything with blkbg isn't needed at all. So this patch is best: diff --git a/block/bio.c b/block/bio.c index 7892f1108ca6..6980f1b4b0f4 100644 --- a/block/bio.c +++ b/block/bio.c @@ -778,9 +778,6 @@ static int __bio_clone(struct bio *bio, struct bio *bio_src, gfp_t gfp) bio->bi_ioprio = bio_src->bi_ioprio; bio->bi_iter = bio_src->bi_iter; - bio_clone_blkg_association(bio, bio_src); - blkcg_bio_issue_init(bio); - if (bio_crypt_clone(bio, bio_src, gfp) < 0) return -ENOMEM; if (bio_integrity(bio_src) && -- dm-devel mailing list [email protected] https://listman.redhat.com/mailman/listinfo/dm-devel
