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>

1 files changed, 10 insertions, 5 deletions

diff --git a/fs/bio.c b/fs/bio.c
index 75c49a382239..8754e7b6eb49 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -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;