[Devel] [PATCH RHEL7 COMMIT] ms/nfsd: don't put blocked locks on LRU until after vfs_lock_file returns

[Vasily Averin]

The commit is pushed to "branch-rh7-3.10.0-1160.42.2.vz7.184.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1160.42.2.vz7.184.4
------>
commit 13a6bf2169ce64ef70474b93de335c93be8b41af
Author: Jeff Layton <jlayton at kernel.org>
Date:   Wed Nov 24 14:50:06 2021 +0300

    ms/nfsd: don't put blocked locks on LRU until after vfs_lock_file returns
    
    Vasily reported a case where vfs_lock_file took a very long time to
    return (longer than a lease period). The laundromat eventually ran and
    reaped the thing and when the vfs_lock_file returned, it ended up
    accessing freed memory.
    
    Don't put entries onto the LRU until vfs_lock_file returns.
    
    Cc: stable at vger.kernel.org
    Fixes: 7919d0a27f1e "nfsd: add a LRU list for blocked locks"
    Reported-by: Vasily Averin <vvs at virtuozzo.com>
    Signed-off-by: Jeff Layton <jlayton at kernel.org>
    Tested-by: Vasily Averin <vvs at virtuozzo.com>
    
    (VvS: should be added to upstream soon)
    https://lore.kernel.org/all/20211123122223.69236-1-jlayton@kernel.org
    https://jira.sw.ru/browse/PSBM-102407
    https://jira.sw.ru/browse/PSBM-121875
    https://jira.sw.ru/browse/PSBM-121984
    https://jira.sw.ru/browse/PSBM-129208
    https://jira.sw.ru/browse/PSBM-129647
    https://jira.sw.ru/browse/PSBM-133020
    https://jira.sw.ru/browse/PSBM-133265
    https://jira.sw.ru/browse/PSBM-133274
    https://jira.sw.ru/browse/PSBM-134762
    https://jira.sw.ru/browse/PSBM-134877
    https://jira.sw.ru/browse/PSBM-134905
    https://jira.sw.ru/browse/PSBM-135845
    Signed-off-by: Vasily Averin <vvs at virtuozzo.com>
---
 fs/nfsd/nfs4state.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 4a57b40..ff64be3 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -5991,10 +5991,8 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	}
 
 	if (fl_flags & FL_SLEEP) {
-		nbl->nbl_time = get_seconds();
 		spin_lock(&nn->blocked_locks_lock);
 		list_add_tail(&nbl->nbl_list, &lock_sop->lo_blocked);
-		list_add_tail(&nbl->nbl_lru, &nn->blocked_locks_lru);
 		spin_unlock(&nn->blocked_locks_lock);
 	}
 
@@ -6005,6 +6003,10 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 		status = 0;
 		break;
 	case FILE_LOCK_DEFERRED:
+		nbl->nbl_time = get_seconds();
+		spin_lock(&nn->blocked_locks_lock);
+		list_add_tail(&nbl->nbl_lru, &nn->blocked_locks_lru);
+		spin_unlock(&nn->blocked_locks_lock);
 		nbl = NULL;
 		/* Fallthrough */
 	case -EAGAIN:		/* conflock holds conflicting lock */