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Commit 892ad71f authored by Dennis Zhou's avatar Dennis Zhou Committed by Jens Axboe
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dm: set the static flush bio device on demand 



The next patch changes the macro bio_set_dev() to associate a bio with a
blkg based on the device set. However, dm creates a static bio to be
used as the basis for cloning empty flush bios on creation. The
bio_set_dev() call in alloc_dev() will cause problems with the next
patch adding association to bio_set_dev() because the call is before the
bdev is associated with a gendisk (bd_disk is %NULL). To get around
this, set the device on the static bio every time and use that to clone
to the other bios.

Signed-off-by: default avatarDennis Zhou <dennis@kernel.org>
Acked-by: default avatarMike Snitzer <snitzer@redhat.com>
Cc: Alasdair Kergon <agk@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 2268c0fe

block/bio.c

+1 −0
Original line number Diff line number Diff line
@@ -2021,6 +2021,7 @@ void bio_disassociate_blkg(struct bio *bio) 
		bio->bi_blkg = NULL;

	}

}

EXPORT_SYMBOL_GPL(bio_disassociate_blkg);



/**

 * __bio_associate_blkg - associate a bio with the a blkg

drivers/md/dm.c

+11 −1
Original line number Diff line number Diff line
@@ -1417,10 +1417,21 @@ static int __send_empty_flush(struct clone_info *ci) 
	unsigned target_nr = 0;

	struct dm_target *ti;



	/*

	 * Empty flush uses a statically initialized bio, &md->flush_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);



	bio_disassociate_blkg(ci->bio);



	return 0;

}
@@ -1939,7 +1950,6 @@ static struct mapped_device *alloc_dev(int minor) 
		goto bad;



	bio_init(&md->flush_bio, NULL, 0);

	bio_set_dev(&md->flush_bio, md->bdev);

	md->flush_bio.bi_opf = REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC;



	dm_stats_init(&md->stats);