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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>
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Kent Overstreet authored and axboe committed Feb 11, 2014
1 parent 9d4cb8e commit 8423ae3d7a3cfe084865262cfaeba1359d405182
Showing with 21 additions and 5 deletions.
  1. +10 −5 fs/bio.c
  2. +11 −0 include/linux/bio.h
View
@@ -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;
View
@@ -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++;

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