From 885848186fbc2d1d8fb6d2fdc2156638ae289a46 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Wed, 13 Jul 2016 16:40:14 -0400 Subject: [PATCH] nfsd: Close race between nfsd4_release_lockowner and nfsd4_lock nfsd4_release_lockowner finds a lock owner that has no lock state, and drops cl_lock. Then release_lockowner picks up cl_lock and unhashes the lock owner. During the window where cl_lock is dropped, I don't see anything preventing a concurrent nfsd4_lock from finding that same lock owner and adding lock state to it. Move release_lockowner() into nfsd4_release_lockowner and hang onto the cl_lock until after the lock owner's state cannot be found again. Found by inspection, we don't currently have a reproducer. Fixes: 2c41beb0e5cf ("nfsd: reduce cl_lock thrashing in ... ") Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever Signed-off-by: J. Bruce Fields --- fs/nfsd/nfs4state.c | 40 +++++++++++++++++----------------------- 1 file changed, 17 insertions(+), 23 deletions(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index bc2173a..8410ca2 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -1200,27 +1200,6 @@ free_ol_stateid_reaplist(struct list_head *reaplist) } } -static void release_lockowner(struct nfs4_lockowner *lo) -{ - struct nfs4_client *clp = lo->lo_owner.so_client; - struct nfs4_ol_stateid *stp; - struct list_head reaplist; - - INIT_LIST_HEAD(&reaplist); - - spin_lock(&clp->cl_lock); - unhash_lockowner_locked(lo); - while (!list_empty(&lo->lo_owner.so_stateids)) { - stp = list_first_entry(&lo->lo_owner.so_stateids, - struct nfs4_ol_stateid, st_perstateowner); - WARN_ON(!unhash_lock_stateid(stp)); - put_ol_stateid_locked(stp, &reaplist); - } - spin_unlock(&clp->cl_lock); - free_ol_stateid_reaplist(&reaplist); - nfs4_put_stateowner(&lo->lo_owner); -} - static void release_open_stateid_locks(struct nfs4_ol_stateid *open_stp, struct list_head *reaplist) { @@ -5963,6 +5942,7 @@ nfsd4_release_lockowner(struct svc_rqst *rqstp, __be32 status; struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id); struct nfs4_client *clp; + LIST_HEAD (reaplist); dprintk("nfsd4_release_lockowner clientid: (%08x/%08x):\n", clid->cl_boot, clid->cl_id); @@ -5993,9 +5973,23 @@ nfsd4_release_lockowner(struct svc_rqst *rqstp, nfs4_get_stateowner(sop); break; } + if (!lo) { + spin_unlock(&clp->cl_lock); + return status; + } + + unhash_lockowner_locked(lo); + while (!list_empty(&lo->lo_owner.so_stateids)) { + stp = list_first_entry(&lo->lo_owner.so_stateids, + struct nfs4_ol_stateid, + st_perstateowner); + WARN_ON(!unhash_lock_stateid(stp)); + put_ol_stateid_locked(stp, &reaplist); + } spin_unlock(&clp->cl_lock); - if (lo) - release_lockowner(lo); + free_ol_stateid_reaplist(&reaplist); + nfs4_put_stateowner(&lo->lo_owner); + return status; } -- 2.7.4