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bcache: comment on direct access to bvec table

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All direct access to bvec table are safe even after multipage bvec is
supported.

Cc: linux-bcache@vger.kernel.org
Acked-by: Coly Li <colyli@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2017-12-18 20:22:09 +08:00 committed by Jens Axboe
parent 8f50e35815
commit c2421edf5f
2 changed files with 8 additions and 0 deletions
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1
drivers/md/bcache/btree.c
View File

@ -432,6 +432,7 @@ static void do_btree_node_write(struct btree *b)
continue_at(cl, btree_node_write_done, NULL);
} else {
/* No problem for multipage bvec since the bio is just allocated */
b->bio->bi_vcnt = 0;
bch_bio_map(b->bio, i);

7
drivers/md/bcache/util.c
View File

@ -249,6 +249,13 @@ uint64_t bch_next_delay(struct bch_ratelimit *d, uint64_t done)
: 0;
}
/*
* Generally it isn't good to access .bi_io_vec and .bi_vcnt directly,
* the preferred way is bio_add_page, but in this case, bch_bio_map()
* supposes that the bvec table is empty, so it is safe to access
* .bi_vcnt & .bi_io_vec in this way even after multipage bvec is
* supported.
*/
void bch_bio_map(struct bio *bio, void *base)
{
size_t size = bio->bi_iter.bi_size;