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block: Fix cloning of discard/write same bios 

Immutable biovecs changed the way bio segments are treated in such a way that
bio_for_each_segment() cannot now do what we want for discard/write same bios,
since bi_size means something completely different for them.

Fortunately discard and write same bios never have more than a single biovec, so
bio_for_each_segment() is unnecessary and not terribly meaningful for them, but
we still have to special case them in a few places.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Tested-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Kent Overstreet 2014-02-10 17:45:50 -08:00 committed by Jens Axboe
parent 9d4cb8e3a5
commit 8423ae3d7a
2 changed files with 21 additions and 5 deletions
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15
fs/bio.c
View File

@ -611,7 +611,6 @@ EXPORT_SYMBOL(bio_clone_fast);
struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
struct bio_set *bs)
{
unsigned nr_iovecs = 0;
struct bvec_iter iter;
struct bio_vec bv;
struct bio *bio;
@ -638,10 +637,7 @@ struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
* __bio_clone_fast() anyways.
*/
bio_for_each_segment(bv, bio_src, iter)
nr_iovecs++;
bio = bio_alloc_bioset(gfp_mask, nr_iovecs, bs);
bio = bio_alloc_bioset(gfp_mask, bio_segments(bio_src), bs);
if (!bio)
return NULL;
@ -650,9 +646,18 @@ struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
bio->bi_iter.bi_sector = bio_src->bi_iter.bi_sector;
bio->bi_iter.bi_size = bio_src->bi_iter.bi_size;
if (bio->bi_rw & REQ_DISCARD)
goto integrity_clone;
if (bio->bi_rw & REQ_WRITE_SAME) {
bio->bi_io_vec[bio->bi_vcnt++] = bio_src->bi_io_vec[0];
goto integrity_clone;
}
bio_for_each_segment(bv, bio_src, iter)
bio->bi_io_vec[bio->bi_vcnt++] = bv;
integrity_clone:
if (bio_integrity(bio_src)) {
int ret;

11
include/linux/bio.h
View File

@ -250,6 +250,17 @@ static inline unsigned bio_segments(struct bio *bio)
struct bio_vec bv;
struct bvec_iter iter;
/*
* We special case discard/write same, because they interpret bi_size
* differently:
*/
if (bio->bi_rw & REQ_DISCARD)
return 1;
if (bio->bi_rw & REQ_WRITE_SAME)
return 1;
bio_for_each_segment(bv, bio, iter)
segs++;