From patchwork Tue Jun 2 07:02:42 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [4/5] dm core: disable interrupt when taking map_lock Date: Tue, 02 Jun 2009 07:02:42 -0000 From: Kiyoshi Ueda X-Patchwork-Id: 27399 This patch disables interrupt when taking map_lock to prevent needless lockdep warnings in request-based dm. request-based dm takes map_lock after taking queue_lock with disabling interrupt: spin_lock_irqsave(queue_lock) q->request_fn() == dm_request_fn() => dm_get_table() => read_lock(map_lock) while queue_lock could be taken in interrupt context. So lockdep warns that a deadlock can happen: write_lock(map_lock) spin_lock_irqsave(queue_lock) q->request_fn() == dm_request_fn() => dm_get_table() => read_lock(map_lock) Currently there is no such code path in request-based dm where q->request_fn() is called from interrupt context, so no such deadlock happens. But such warning messages confuse users, so prevent them by disabling interrupt when taking map_lock. Signed-off-by: Kiyoshi Ueda Signed-off-by: Jun'ichi Nomura Acked-by: Christof Schmitt Acked-by: Hannes Reinecke Cc: Alasdair G Kergon --- drivers/md/dm.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel Index: linux-2.6-block/drivers/md/dm.c =================================================================== --- linux-2.6-block.orig/drivers/md/dm.c +++ linux-2.6-block/drivers/md/dm.c @@ -508,12 +508,13 @@ static void queue_io(struct mapped_devic struct dm_table *dm_get_table(struct mapped_device *md) { struct dm_table *t; + unsigned long flags; - read_lock(&md->map_lock); + read_lock_irqsave(&md->map_lock, flags); t = md->map; if (t) dm_table_get(t); - read_unlock(&md->map_lock); + read_unlock_irqrestore(&md->map_lock, flags); return t; } @@ -1960,6 +1961,7 @@ static int __bind(struct mapped_device * { struct request_queue *q = md->queue; sector_t size; + unsigned long flags; size = dm_table_get_size(t); @@ -1990,10 +1992,10 @@ static int __bind(struct mapped_device * __bind_mempools(md, t); - write_lock(&md->map_lock); + write_lock_irqsave(&md->map_lock, flags); md->map = t; dm_table_set_restrictions(t, q); - write_unlock(&md->map_lock); + write_unlock_irqrestore(&md->map_lock, flags); return 0; } @@ -2001,14 +2003,15 @@ static int __bind(struct mapped_device * static void __unbind(struct mapped_device *md) { struct dm_table *map = md->map; + unsigned long flags; if (!map) return; dm_table_event_callback(map, NULL, NULL); - write_lock(&md->map_lock); + write_lock_irqsave(&md->map_lock, flags); md->map = NULL; - write_unlock(&md->map_lock); + write_unlock_irqrestore(&md->map_lock, flags); dm_table_destroy(map); }