[PATCH 64/78] dm: simplify flush_bio initialization in __send_empty_flush

[Hannes Reinecke]

On 11/16/20 3:57 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 at lst.de>
> ---
>   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 54739f1b579bc8..6d7eb72d41f9ea 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);
> 
Ah, thought as much. I've stumbled across this while debugging 
blk-interposer.

Reviewed-by: Hannes Reinecke <hare at suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
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