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| author | Joe Thornber <ejt@redhat.com> | 2014-10-10 09:41:09 +0100 |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2014-11-19 18:38:20 +0100 |
| commit | 2c49ae544b24a61a8de26c7bf0bce13151d54abf (patch) | |
| tree | e3f3ba3c07fe1f73c77abc73fbbc03dd68a4df95 | |
| parent | f0a72a0e7c682320fa38e71612008de3e3d796ca (diff) | |
| download | lwn-2c49ae544b24a61a8de26c7bf0bce13151d54abf.tar.gz lwn-2c49ae544b24a61a8de26c7bf0bce13151d54abf.zip | |
dm thin: grab a virtual cell before looking up the mapping
commit c822ed967cba38505713d59ed40a114386ef6c01 upstream.
Avoids normal IO racing with discard.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
| -rw-r--r-- | drivers/md/dm-thin.c | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index f8c36d30eca8..0396d7fc1d8b 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -1504,6 +1504,14 @@ 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); /* @@ -1527,13 +1535,10 @@ 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); @@ -1554,6 +1559,7 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio) * of doing so. Just error it. */ bio_io_error(bio); + cell_defer_no_holder_no_free(tc, &cell1); return DM_MAPIO_SUBMITTED; } /* fall through */ @@ -1564,6 +1570,7 @@ 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: @@ -1573,6 +1580,7 @@ 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; } } |