On 09/08/2010 04:04 AM, Mike Snitzer wrote:
> Rename __clone_and_map_flush to __clone_and_map_empty_flush for added
> clarity.
>
> Simplify logic associated with REQ_FLUSH conditionals.
>
> Introduce a BUG_ON() and add a few more helpful comments to the code
> so that it is clear that all flushes are empty.
>
> Cleanup __split_and_process_bio() so that an empty flush isn't processed
> by a 'sector_count' focused while loop.
>
> Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
> ---
> drivers/md/dm.c | 34 +++++++++++++++-------------------
> 1 files changed, 15 insertions(+), 19 deletions(-)
>
> Tejun, please feel free to fold this patch into (or insert after)
> 0025-dm-relax-ordering-of-bio-based-flush-implementation.patch
>
> v2: Simplify logic associated with REQ_FLUSH conditionals
>
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index cd2f7e7..f934e98 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -621,16 +621,17 @@ static void dec_pending(struct dm_io *io, int error)
> if (io_error == DM_ENDIO_REQUEUE)
> return;
>
> - if (!(bio->bi_rw & REQ_FLUSH) || !bio->bi_size) {
> - trace_block_bio_complete(md->queue, bio);
> - bio_endio(bio, io_error);
> - } else {
> + if ((bio->bi_rw & REQ_FLUSH) && bio->bi_size) {
> /*
> * Preflush done for flush with data, reissue
> * without REQ_FLUSH.
> */
> bio->bi_rw &= ~REQ_FLUSH;
> queue_io(md, bio);
> + } else {
> + /* done with normal IO or empty flush */
> + trace_block_bio_complete(md->queue, bio);
> + bio_endio(bio, io_error);
> }
> }
> }
> @@ -1132,16 +1133,15 @@ static void __issue_target_requests(struct clone_info *ci, struct dm_target *ti,
> __issue_target_request(ci, ti, request_nr, len);
> }
>
> -static int __clone_and_map_flush(struct clone_info *ci)
> +static int __clone_and_map_empty_flush(struct clone_info *ci)
> {
> unsigned target_nr = 0;
> struct dm_target *ti;
>
> + BUG_ON(bio_has_data(ci->bio));
> while ((ti = dm_table_get_target(ci->map, target_nr++)))
> __issue_target_requests(ci, ti, ti->num_flush_requests, 0);
>
> - ci->sector_count = 0;
> -
> return 0;
> }
>
> @@ -1282,7 +1282,6 @@ static int __clone_and_map(struct clone_info *ci)
> */
> static void __split_and_process_bio(struct mapped_device *md, struct bio *bio)
> {
> - bool is_flush = bio->bi_rw & REQ_FLUSH;
> struct clone_info ci;
> int error = 0;
>
> @@ -1302,20 +1301,17 @@ static void __split_and_process_bio(struct mapped_device *md, struct bio *bio)
> ci.sector = bio->bi_sector;
> ci.idx = bio->bi_idx;
>
> - if (!is_flush) {
> + start_io_acct(ci.io);
> + if (bio->bi_rw & REQ_FLUSH) {
> + ci.bio = &ci.md->flush_bio;
> + ci.sector_count = 0;
> + error = __clone_and_map_empty_flush(&ci);
> + /* dec_pending submits any data associated with flush */
> + } else {
> ci.bio = bio;
> ci.sector_count = bio_sectors(bio);
> - } else {
> - ci.bio = &ci.md->flush_bio;
> - ci.sector_count = 1;
> - }
> -
> - start_io_acct(ci.io);
> - while (ci.sector_count && !error) {
> - if (!is_flush)
> + while (ci.sector_count && !error)
> error = __clone_and_map(&ci);
> - else
> - error = __clone_and_map_flush(&ci);
> }
>
> /* drop the extra reference count */
--
tejun
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