This is a note to let you know that I've just added the patch titled
NFSD: Leave open files out of the filecache LRU
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
nfsd-leave-open-files-out-of-the-filecache-lru.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit a664e97085f11088c8d05f49857065da96d0c6cb
Author: Chuck Lever <chuck.lever@xxxxxxxxxx>
Date: Fri Jul 8 14:25:17 2022 -0400
NFSD: Leave open files out of the filecache LRU
[ Upstream commit 4a0e73e635e3f36b616ad5c943e3d23debe4632f ]
There have been reports of problems when running fstests generic/531
against Linux NFS servers with NFSv4. The NFS server that hosts the
test's SCRATCH_DEV suffers from CPU soft lock-ups during the test.
Analysis shows that:
fs/nfsd/filecache.c
482 ret = list_lru_walk(&nfsd_file_lru,
483 nfsd_file_lru_cb,
484 &head, LONG_MAX);
causes nfsd_file_gc() to walk the entire length of the filecache LRU
list every time it is called (which is quite frequently). The walk
holds a spinlock the entire time that prevents other nfsd threads
from accessing the filecache.
What's more, for NFSv4 workloads, none of the items that are visited
during this walk may be evicted, since they are all files that are
held OPEN by NFS clients.
Address this by ensuring that open files are not kept on the LRU
list.
Reported-by: Frank van der Linden <fllinden@xxxxxxxxxx>
Reported-by: Wang Yugui <wangyugui@xxxxxxxxxxxx>
Link: https://bugzilla.linux-nfs.org/show_bug.cgi?id=386
Suggested-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index a995a744a7481..5c9e3ff6397b0 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -262,6 +262,7 @@ nfsd_file_flush(struct nfsd_file *nf)
static void nfsd_file_lru_add(struct nfsd_file *nf)
{
+ set_bit(NFSD_FILE_REFERENCED, &nf->nf_flags);
if (list_lru_add(&nfsd_file_lru, &nf->nf_lru))
trace_nfsd_file_lru_add(nf);
}
@@ -291,7 +292,6 @@ nfsd_file_unhash(struct nfsd_file *nf)
{
if (test_and_clear_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {
nfsd_file_do_unhash(nf);
- nfsd_file_lru_remove(nf);
return true;
}
return false;
@@ -312,6 +312,7 @@ nfsd_file_unhash_and_release_locked(struct nfsd_file *nf, struct list_head *disp
if (refcount_dec_not_one(&nf->nf_ref))
return true;
+ nfsd_file_lru_remove(nf);
list_add(&nf->nf_lru, dispose);
return true;
}
@@ -323,6 +324,7 @@ nfsd_file_put_noref(struct nfsd_file *nf)
if (refcount_dec_and_test(&nf->nf_ref)) {
WARN_ON(test_bit(NFSD_FILE_HASHED, &nf->nf_flags));
+ nfsd_file_lru_remove(nf);
nfsd_file_free(nf);
}
}
@@ -332,7 +334,7 @@ nfsd_file_put(struct nfsd_file *nf)
{
might_sleep();
- set_bit(NFSD_FILE_REFERENCED, &nf->nf_flags);
+ nfsd_file_lru_add(nf);
if (test_bit(NFSD_FILE_HASHED, &nf->nf_flags) == 0) {
nfsd_file_flush(nf);
nfsd_file_put_noref(nf);
@@ -432,8 +434,18 @@ nfsd_file_dispose_list_delayed(struct list_head *dispose)
}
}
-/*
+/**
+ * nfsd_file_lru_cb - Examine an entry on the LRU list
+ * @item: LRU entry to examine
+ * @lru: controlling LRU
+ * @lock: LRU list lock (unused)
+ * @arg: dispose list
+ *
* Note this can deadlock with nfsd_file_cache_purge.
+ *
+ * Return values:
+ * %LRU_REMOVED: @item was removed from the LRU
+ * %LRU_SKIP: @item cannot be evicted
*/
static enum lru_status
nfsd_file_lru_cb(struct list_head *item, struct list_lru_one *lru,
@@ -455,8 +467,9 @@ nfsd_file_lru_cb(struct list_head *item, struct list_lru_one *lru,
* That order is deliberate to ensure that we can do this locklessly.
*/
if (refcount_read(&nf->nf_ref) > 1) {
+ list_lru_isolate(lru, &nf->nf_lru);
trace_nfsd_file_gc_in_use(nf);
- return LRU_SKIP;
+ return LRU_REMOVED;
}
/*
@@ -1013,6 +1026,7 @@ nfsd_do_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
goto retry;
}
+ nfsd_file_lru_remove(nf);
this_cpu_inc(nfsd_file_cache_hits);
status = nfserrno(nfsd_open_break_lease(file_inode(nf->nf_file), may_flags));
@@ -1034,7 +1048,6 @@ nfsd_do_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
refcount_inc(&nf->nf_ref);
__set_bit(NFSD_FILE_HASHED, &nf->nf_flags);
__set_bit(NFSD_FILE_PENDING, &nf->nf_flags);
- nfsd_file_lru_add(nf);
hlist_add_head_rcu(&nf->nf_node, &nfsd_file_hashtbl[hashval].nfb_head);
++nfsd_file_hashtbl[hashval].nfb_count;
nfsd_file_hashtbl[hashval].nfb_maxcount = max(nfsd_file_hashtbl[hashval].nfb_maxcount,
@@ -1059,6 +1072,7 @@ nfsd_do_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
*/
if (status != nfs_ok || inode->i_nlink == 0) {
bool do_free;
+ nfsd_file_lru_remove(nf);
spin_lock(&nfsd_file_hashtbl[hashval].nfb_lock);
do_free = nfsd_file_unhash(nf);
spin_unlock(&nfsd_file_hashtbl[hashval].nfb_lock);
diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
index 40ee80b6a2a79..d32ecbdfd0786 100644
--- a/fs/nfsd/trace.h
+++ b/fs/nfsd/trace.h
@@ -926,7 +926,9 @@ DEFINE_EVENT(nfsd_file_gc_class, name, \
TP_ARGS(nf))
DEFINE_NFSD_FILE_GC_EVENT(nfsd_file_lru_add);
+DEFINE_NFSD_FILE_GC_EVENT(nfsd_file_lru_add_disposed);
DEFINE_NFSD_FILE_GC_EVENT(nfsd_file_lru_del);
+DEFINE_NFSD_FILE_GC_EVENT(nfsd_file_lru_del_disposed);
DEFINE_NFSD_FILE_GC_EVENT(nfsd_file_gc_in_use);
DEFINE_NFSD_FILE_GC_EVENT(nfsd_file_gc_writeback);
DEFINE_NFSD_FILE_GC_EVENT(nfsd_file_gc_referenced);
