Re: [PATCH v1 23/54] bcache: handle bio_clone() & bvec updating for multipage bvecs

Hi Coly,

On Fri, Dec 30, 2016 at 7:01 PM, Coly Li [off-list ref] wrote:

On 2016/12/27 下午11:56, Ming Lei wrote:

quoted

The incoming bio may be too big to be cloned into
one singlepage bvecs bio, so split the bio and
check the splitted bio one by one.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/md/bcache/debug.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/md/bcache/debug.c b/drivers/md/bcache/debug.c
index 48d03e8b3385..18b2d2d138e3 100644
--- a/drivers/md/bcache/debug.c
+++ b/drivers/md/bcache/debug.c

@@ -103,7 +103,7 @@ void bch_btree_verify(struct btree *b)
      up(&b->io_mutex);
 }

-void bch_data_verify(struct cached_dev *dc, struct bio *bio)
+static void __bch_data_verify(struct cached_dev *dc, struct bio *bio)
 {
      char name[BDEVNAME_SIZE];
      struct bio *check;

@@ -116,7 +116,7 @@ void bch_data_verify(struct cached_dev *dc, struct bio *bio)
       * in the new cloned bio because each single page need
       * to assign to each bvec of the new bio.
       */
-     check = bio_clone(bio, GFP_NOIO);
+     check = bio_clone_sp(bio, GFP_NOIO);
      if (!check)
              return;
      check->bi_opf = REQ_OP_READ;

@@ -151,6 +151,26 @@ void bch_data_verify(struct cached_dev *dc, struct bio *bio)
      bio_put(check);
 }

+void bch_data_verify(struct cached_dev *dc, struct bio *bio)
+{
+     struct request_queue *q = bdev_get_queue(bio->bi_bdev);
+     struct bio *clone = bio_clone_fast(bio, GFP_NOIO, q->bio_split);
+     unsigned sectors;
+
+     while (!bio_can_convert_to_sp(clone, &sectors)) {
+             struct bio *split = bio_split(clone, sectors,
+                                           GFP_NOIO, q->bio_split);
+
+             __bch_data_verify(dc, split);
+             bio_put(split);
+     }
+
+     if (bio_sectors(clone))
+             __bch_data_verify(dc, clone);
+
+     bio_put(clone);
+}
+

Hi Lei,

The above patch is good IMHO. Just wondering why not use the classical
style ? something like,

I don't know there is the classical style, :-)

do {
        if (!bio_can_convert_to_sp(clone, &sectors))
                split = bio_split(clone, sectors,
                                  GFP_NOIO, q->bio_split);
        else
                split = clone;

        __bch_data_verity(gc, split);
        bio_put(split);
} while (split != clone);


I guess maybe the above style generates less binary code.

Maybe, will take this style in V2.

Thanks for the review!

-- 
Ming Lei