Re: [PATCH 08/45] dm: simplify flush_bio initialization in __send_empty_flush

Hannes Reinecke
2020-11-30T07:09:35Z

On 11/28/20 5:14 PM, Christoph Hellwig wrote:
> We don't really need the struct block_device to initialize a bio. So
> switch from using bio_set_dev to manually setting up bi_disk (bi_partno
> will always be zero and has been cleared by bio_init already).
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Acked-by: Mike Snitzer <snitzer@redhat.com>
> ---
> drivers/md/dm.c | 12 +++---------
> 1 file changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 50541d336c719b..ab0a8335f098d9 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -1422,18 +1422,12 @@ static int __send_empty_flush(struct clone_info *ci)
> */
> bio_init(&flush_bio, NULL, 0);
> flush_bio.bi_opf = REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC;
> + flush_bio.bi_disk = ci->io->md->disk;
> + bio_associate_blkg(&flush_bio);
> +
> ci->bio = &flush_bio;
> ci->sector_count = 0;
>
> - /*
> - * Empty flush uses a statically initialized bio, as the base for
> - * cloning. However, blkg association requires that a bdev is
> - * associated with a gendisk, which doesn't happen until the bdev is
> - * opened. So, blkg association is done at issue time of the flush
> - * rather than when the device is created in alloc_dev().
> - */
> - bio_set_dev(ci->bio, ci->io->md->bdev);
> -
> BUG_ON(bio_has_data(ci->bio));
> while ((ti = dm_table_get_target(ci->map, target_nr++)))
> __send_duplicate_bios(ci, ti, ti->num_flush_bios, NULL);
>
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
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