[PATCH V4 07/45] bcache: comment on direct access to bvec table
From: Ming Lei <hidden>
Date: 2017-12-18 12:22:09
Also in:
linux-block, linux-fsdevel, linux-mm, lkml
Subsystem:
bcache (block layer cache), the rest · Maintainers:
Coly Li, Kent Overstreet, Linus Torvalds
All direct access to bvec table are safe even after multipage bvec is supported. Cc: linux-bcache@vger.kernel.org Acked-by: Coly Li <redacted> Signed-off-by: Ming Lei <redacted> --- drivers/md/bcache/btree.c | 1 + drivers/md/bcache/util.c | 7 +++++++ 2 files changed, 8 insertions(+)
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 81e8dc3dbe5e..02a4cf646fdc 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c@@ -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);
diff --git a/drivers/md/bcache/util.c b/drivers/md/bcache/util.c
index e548b8b51322..61813d230015 100644
--- a/drivers/md/bcache/util.c
+++ b/drivers/md/bcache/util.c@@ -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;
--
2.9.5
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