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dm thin: grab a virtual cell before looking up the mapping

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Avoids normal IO racing with discard.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
This commit is contained in:
Joe Thornber 2014-10-10 09:41:09 +01:00 committed by Mike Snitzer
parent d20c4b08be
commit c822ed967c
1 changed files with 12 additions and 4 deletions
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16
drivers/md/dm-thin.c
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@ -1936,6 +1936,14 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio)
return DM_MAPIO_SUBMITTED;
}
/*
* We must hold the virtual cell before doing the lookup, otherwise
* there's a race with discard.
*/
build_virtual_key(tc->td, block, &key);
if (dm_bio_detain(tc->pool->prison, &key, bio, &cell1, &cell_result))
return DM_MAPIO_SUBMITTED;
r = dm_thin_find_block(td, block, 0, &result);
/*
@ -1959,13 +1967,10 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio)
* shared flag will be set in their case.
*/
thin_defer_bio(tc, bio);
cell_defer_no_holder_no_free(tc, &cell1);
return DM_MAPIO_SUBMITTED;
}
build_virtual_key(tc->td, block, &key);
if (dm_bio_detain(tc->pool->prison, &key, bio, &cell1, &cell_result))
return DM_MAPIO_SUBMITTED;
build_data_key(tc->td, result.block, &key);
if (dm_bio_detain(tc->pool->prison, &key, bio, &cell2, &cell_result)) {
cell_defer_no_holder_no_free(tc, &cell1);
@ -1986,6 +1991,7 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio)
* of doing so.
*/
handle_unserviceable_bio(tc->pool, bio);
cell_defer_no_holder_no_free(tc, &cell1);
return DM_MAPIO_SUBMITTED;
}
/* fall through */
@ -1996,6 +2002,7 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio)
* provide the hint to load the metadata into cache.
*/
thin_defer_bio(tc, bio);
cell_defer_no_holder_no_free(tc, &cell1);
return DM_MAPIO_SUBMITTED;
default:
@ -2005,6 +2012,7 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio)
* pool is switched to fail-io mode.
*/
bio_io_error(bio);
cell_defer_no_holder_no_free(tc, &cell1);
return DM_MAPIO_SUBMITTED;
}
}