4.14-stable review patch. If anyone has any objections, please let me know.
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From: Nate Dailey nate.dailey@stratus.com
commit f6eca2d43ed694ab8124dd24c88277f7eca93b7d upstream.
If freeze_array is attempted in the middle of close_sync/ wait_all_barriers, deadlock can occur.
freeze_array will wait for nr_pending and nr_queued to line up. wait_all_barriers increments nr_pending for each barrier bucket, one at a time, but doesn't actually issue IO that could be counted in nr_queued. So freeze_array is blocked until wait_all_barriers completes and allow_all_barriers runs. At the same time, when _wait_barrier sees array_frozen == 1, it stops and waits for freeze_array to complete.
Prevent the deadlock by making close_sync call _wait_barrier and _allow_barrier for one bucket at a time, instead of deferring the _allow_barrier calls until after all _wait_barriers are complete.
Signed-off-by: Nate Dailey nate.dailey@stratus.com Fix: fd76863e37fe(RAID1: a new I/O barrier implementation to remove resync window) Reviewed-by: Coly Li colyli@suse.de Signed-off-by: Shaohua Li shli@fb.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/md/raid1.c | 24 ++++++------------------ 1 file changed, 6 insertions(+), 18 deletions(-)
--- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -990,14 +990,6 @@ static void wait_barrier(struct r1conf * _wait_barrier(conf, idx); }
-static void wait_all_barriers(struct r1conf *conf) -{ - int idx; - - for (idx = 0; idx < BARRIER_BUCKETS_NR; idx++) - _wait_barrier(conf, idx); -} - static void _allow_barrier(struct r1conf *conf, int idx) { atomic_dec(&conf->nr_pending[idx]); @@ -1011,14 +1003,6 @@ static void allow_barrier(struct r1conf _allow_barrier(conf, idx); }
-static void allow_all_barriers(struct r1conf *conf) -{ - int idx; - - for (idx = 0; idx < BARRIER_BUCKETS_NR; idx++) - _allow_barrier(conf, idx); -} - /* conf->resync_lock should be held */ static int get_unqueued_pending(struct r1conf *conf) { @@ -1654,8 +1638,12 @@ static void print_conf(struct r1conf *co
static void close_sync(struct r1conf *conf) { - wait_all_barriers(conf); - allow_all_barriers(conf); + int idx; + + for (idx = 0; idx < BARRIER_BUCKETS_NR; idx++) { + _wait_barrier(conf, idx); + _allow_barrier(conf, idx); + }
mempool_destroy(conf->r1buf_pool); conf->r1buf_pool = NULL;