5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Chuck Lever chuck.lever@oracle.com
[ 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@amazon.com Reported-by: Wang Yugui wangyugui@e16-tech.com Link: https://bugzilla.linux-nfs.org/show_bug.cgi?id=386 Suggested-by: Trond Myklebust trond.myklebust@hammerspace.com Reviewed-by: Jeff Layton jlayton@kernel.org Signed-off-by: Chuck Lever chuck.lever@oracle.com --- fs/nfsd/filecache.c | 24 +++++++++++++++++++----- fs/nfsd/trace.h | 2 ++ 2 files changed, 21 insertions(+), 5 deletions(-)
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 c47f46d433ddb..cc55a2b32e8cd 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);