[PATCH 1/1] NFSD: fix WARN_ON_ONCE in __queue_delayed_work
From: Dai Ngo <dai.ngo@oracle.com>
Date: 2023-01-10 06:49:04
Subsystem:
filesystems (vfs and infrastructure), kernel nfsd, sunrpc, and lockd servers, the rest · Maintainers:
Alexander Viro, Christian Brauner, Chuck Lever, Jeff Layton, Linus Torvalds
Currently nfsd4_state_shrinker_worker can be schduled multiple times
from nfsd4_state_shrinker_count when memory is low. This causes
the WARN_ON_ONCE in __queue_delayed_work to trigger.
This patch allows only one instance of nfsd4_state_shrinker_worker
at a time using the nfsd_shrinker_active flag, protected by the
client_lock.
Replace mod_delayed_work with queue_delayed_work since we
don't expect to modify the delay of any pending work.
Fixes: 44df6f439a17 ("NFSD: add delegation reaper to react to low memory condition")
Reported-by: Mike Galbraith <redacted>
Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
---
fs/nfsd/netns.h | 1 +
fs/nfsd/nfs4state.c | 16 ++++++++++++++--
2 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
index 8c854ba3285b..801d70926442 100644
--- a/fs/nfsd/netns.h
+++ b/fs/nfsd/netns.h@@ -196,6 +196,7 @@ struct nfsd_net { atomic_t nfsd_courtesy_clients; struct shrinker nfsd_client_shrinker; struct delayed_work nfsd_shrinker_work; + bool nfsd_shrinker_active; }; /* Simple check to find out if a given net was properly initialized */
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index ee56c9466304..e00551af6a11 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c@@ -4407,11 +4407,20 @@ nfsd4_state_shrinker_count(struct shrinker *shrink, struct shrink_control *sc) struct nfsd_net *nn = container_of(shrink, struct nfsd_net, nfsd_client_shrinker); + spin_lock(&nn->client_lock); + if (nn->nfsd_shrinker_active) { + spin_unlock(&nn->client_lock); + return 0; + } count = atomic_read(&nn->nfsd_courtesy_clients); if (!count) count = atomic_long_read(&num_delegations); - if (count) - mod_delayed_work(laundry_wq, &nn->nfsd_shrinker_work, 0); + if (count) { + nn->nfsd_shrinker_active = true; + spin_unlock(&nn->client_lock); + queue_delayed_work(laundry_wq, &nn->nfsd_shrinker_work, 0); + } else + spin_unlock(&nn->client_lock); return (unsigned long)count; }
@@ -6239,6 +6248,9 @@ nfsd4_state_shrinker_worker(struct work_struct *work) courtesy_client_reaper(nn); deleg_reaper(nn); + spin_lock(&nn->client_lock); + nn->nfsd_shrinker_active = 0; + spin_unlock(&nn->client_lock); } static inline __be32 nfs4_check_fh(struct svc_fh *fhp, struct nfs4_stid *stp)
--
2.9.5