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dm: set the static flush bio device on demand

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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: Dennis Zhou <dennis@kernel.org>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Cc: Alasdair Kergon <agk@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Dennis Zhou 2018-12-05 12:10:30 -05:00 committed by Jens Axboe
parent 2268c0feb0
commit 892ad71f62
2 changed files with 12 additions and 1 deletions
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1
block/bio.c
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@ -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

12
drivers/md/dm.c
View File

@ -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);