From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kiyoshi Ueda Subject: [PATCH 4/8] dm core: disable interrupt when taking map_lock Date: Wed, 18 Mar 2009 17:54:36 +0900 Message-ID: <49C0B6CC.2090005@ct.jp.nec.com> References: <49C0B474.4000204@ct.jp.nec.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <49C0B474.4000204@ct.jp.nec.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Alasdair Kergon Cc: Christof Schmitt , device-mapper development List-Id: dm-devel.ids 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 Cc: Christof Schmitt Cc: Alasdair G Kergon --- drivers/md/dm.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) Index: 2.6.29-rc8/drivers/md/dm.c =================================================================== --- 2.6.29-rc8.orig/drivers/md/dm.c +++ 2.6.29-rc8/drivers/md/dm.c @@ -511,12 +511,13 @@ static int queue_io(struct mapped_device 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; } @@ -1929,6 +1930,7 @@ static int __bind(struct mapped_device * { struct request_queue *q = md->queue; sector_t size; + unsigned long flags; size = dm_table_get_size(t); @@ -1960,10 +1962,10 @@ 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; } @@ -1971,14 +1973,15 @@ 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); }