diff options
| author | Chandra Seetharaman <sekharan@us.ibm.com> | 2008-11-13 23:39:14 +0000 |
|---|---|---|
| committer | Alasdair G Kergon <agk@redhat.com> | 2008-11-13 23:39:14 +0000 |
| commit | 8a57dfc6f943c92b861c9a19b0c86ddcb2aba768 (patch) | |
| tree | 18090d42e647cda854c93aa304cf03fbad44f6c0 /drivers/md | |
| parent | d221d2e77696e70e94b13989ea15db2ba5b34f8e (diff) | |
| download | linux-8a57dfc6f943c92b861c9a19b0c86ddcb2aba768.tar.bz2 | |
dm: avoid destroying table in dm_any_congested
dm_any_congested() just checks for the DMF_BLOCK_IO and has no
code to make sure that suspend waits for dm_any_congested() to
complete. This patch adds such a check.
Without it, a race can occur with dm_table_put() attempting to
destroying the table in the wrong thread, the one running
dm_any_congested() which is meant to be quick and return
immediately.
Two examples of problems:
1. Sleeping functions called from congested code, the caller
of which holds a spin lock.
2. An ABBA deadlock between pdflush and multipathd. The two locks
in contention are inode lock and kernel lock.
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md')
| -rw-r--r-- | drivers/md/dm.c | 24 |
1 files changed, 16 insertions, 8 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c index dc25d8a07bc7..c99e4728ff41 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -937,16 +937,24 @@ static void dm_unplug_all(struct request_queue *q) static int dm_any_congested(void *congested_data, int bdi_bits) { - int r; - struct mapped_device *md = (struct mapped_device *) congested_data; - struct dm_table *map = dm_get_table(md); + int r = bdi_bits; + struct mapped_device *md = congested_data; + struct dm_table *map; - if (!map || test_bit(DMF_BLOCK_IO, &md->flags)) - r = bdi_bits; - else - r = dm_table_any_congested(map, bdi_bits); + atomic_inc(&md->pending); + + if (!test_bit(DMF_BLOCK_IO, &md->flags)) { + map = dm_get_table(md); + if (map) { + r = dm_table_any_congested(map, bdi_bits); + dm_table_put(map); + } + } + + if (!atomic_dec_return(&md->pending)) + /* nudge anyone waiting on suspend queue */ + wake_up(&md->wait); - dm_table_put(map); return r; } |