bcache: Fix flash_dev_cache_miss() for real this time

The code was using sectors to count the number of sectors it was zeroing... but
then it passed it to bio_advance()... after it had been set to 0. Amusing...

Signed-off-by: Kent Overstreet <kmo@daterainc.com>

1 files changed, 5 insertions, 14 deletions

diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
index 5d5d031cf381..fc14ba3f6d05 100644
--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -1203,22 +1203,13 @@ void bch_cached_dev_request_init(struct cached_dev *dc)
 static int flash_dev_cache_miss(struct btree *b, struct search *s,
                                 struct bio *bio, unsigned sectors)
 {
-        struct bio_vec bv;
-        struct bvec_iter iter;
-
-        /* Zero fill bio */
-
-        bio_for_each_segment(bv, bio, iter) {
-                unsigned j = min(bv.bv_len >> 9, sectors);
-
-                void *p = kmap(bv.bv_page);
-                memset(p + bv.bv_offset, 0, j << 9);
-                kunmap(bv.bv_page);
+        unsigned bytes = min(sectors, bio_sectors(bio)) << 9;
 
-                sectors -= j;
-        }
+        swap(bio->bi_iter.bi_size, bytes);
+        zero_fill_bio(bio);
+        swap(bio->bi_iter.bi_size, bytes);
 
-        bio_advance(bio, min(sectors << 9, bio->bi_iter.bi_size));
+        bio_advance(bio, bytes);
 
         if (!bio->bi_iter.bi_size)
                 return MAP_DONE;