From 6e377faf4490f20a63634c8baecb76886c0dac8a Mon Sep 17 00:00:00 2001 From: Pranith Kumar K Date: Tue, 13 Jun 2017 23:35:40 +0530 Subject: cluster/ec: lk shouldn't be a transaction Problem: When application sends a blocking lock, the lk fop actually waits under inodelk. This can lead to a dead-lock. 1) Let's say app-1 takes exculsive-fcntl-lock on the file 2) app-2 attempts an exclusive-fcntl-lock on the file which goes to blocking stage note: app-2 is blocked inside transaction which holds an inode-lock 3) app-1 tries to perform write which needs inode-lock so it gets blocked on app-2 to unlock inodelk and app-2 is blocked on app-1 to unlock fcntl-lock Fix: Correct way to fix this issue and make fcntl locks perform well would be to introduce 2-phase locking for fcntl lock: 1) Implement a try-lock phase where locks xlator will not merge lk call with existing calls until a commit-lock phase. 2) If in try-lock phase we get quorum number of success without any EAGAIN error, then send a commit-lock which will merge locks. 3) In case there are any errors, unlock should just delete the lock-object which was tried earlier and shouldn't touch the committed locks. Unfortunately this is a sizeable feature and need to be thought through for any corner cases. Until then remove transaction from lk call. >BUG: 1455049 >Change-Id: I18a782903ba0eb43f1e6526fb0cf8c626c460159 >Signed-off-by: Pranith Kumar K >Reviewed-on: https://review.gluster.org/17542 >Smoke: Gluster Build System >NetBSD-regression: NetBSD Build System >CentOS-regression: Gluster Build System >Reviewed-by: Ashish Pandey >Reviewed-by: Xavier Hernandez BUG: 1462121 Change-Id: I18a782903ba0eb43f1e6526fb0cf8c626c460159 Signed-off-by: Pranith Kumar K Reviewed-on: https://review.gluster.org/17556 Smoke: Gluster Build System NetBSD-regression: NetBSD Build System CentOS-regression: Gluster Build System Reviewed-by: Shyamsundar Ranganathan --- xlators/cluster/ec/src/ec-locks.c | 20 +------------------- 1 file changed, 1 insertion(+), 19 deletions(-) (limited to 'xlators') diff --git a/xlators/cluster/ec/src/ec-locks.c b/xlators/cluster/ec/src/ec-locks.c index 70b07c318e0..ff098522f18 100644 --- a/xlators/cluster/ec/src/ec-locks.c +++ b/xlators/cluster/ec/src/ec-locks.c @@ -1020,12 +1020,6 @@ int32_t ec_manager_lk(ec_fop_data_t * fop, int32_t state) /* Fall through */ - case EC_STATE_LOCK: - ec_lock_prepare_fd(fop, fop->fd, EC_UPDATE_DATA | EC_QUERY_INFO); - ec_lock(fop); - - return EC_STATE_DISPATCH; - case EC_STATE_DISPATCH: ec_dispatch_all(fop); @@ -1080,10 +1074,9 @@ int32_t ec_manager_lk(ec_fop_data_t * fop, int32_t state) cbk->op_errno, &cbk->flock, cbk->xdata); } - return EC_STATE_LOCK_REUSE; + return EC_STATE_END; case -EC_STATE_INIT: - case -EC_STATE_LOCK: case -EC_STATE_DISPATCH: case -EC_STATE_REPORT: GF_ASSERT(fop->error != 0); @@ -1094,17 +1087,6 @@ int32_t ec_manager_lk(ec_fop_data_t * fop, int32_t state) NULL, NULL); } - return EC_STATE_LOCK_REUSE; - - case -EC_STATE_LOCK_REUSE: - case EC_STATE_LOCK_REUSE: - ec_lock_reuse(fop); - - return EC_STATE_UNLOCK; - - case -EC_STATE_UNLOCK: - case EC_STATE_UNLOCK: - ec_unlock(fop); return EC_STATE_END; -- cgit