From patchwork Tue Jun 28 18:07:23 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chuck Lever III X-Patchwork-Id: 12898646 X-Patchwork-Delegate: kuba@kernel.org Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE01ACCA47F for ; Tue, 28 Jun 2022 18:07:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234209AbiF1SHe (ORCPT ); Tue, 28 Jun 2022 14:07:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51478 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233994AbiF1SH2 (ORCPT ); Tue, 28 Jun 2022 14:07:28 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9ABA21EAD6; Tue, 28 Jun 2022 11:07:27 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 3F283B81F38; Tue, 28 Jun 2022 18:07:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 93B42C3411D; Tue, 28 Jun 2022 18:07:24 +0000 (UTC) Subject: [PATCH v2 15/31] NFSD: Leave open files out of the filecache LRU From: Chuck Lever To: linux-nfs@vger.kernel.org, netdev@vger.kernel.org Cc: david@fromorbit.com, jlayton@redhat.com, tgraf@suug.ch Date: Tue, 28 Jun 2022 14:07:23 -0400 Message-ID: <165643964363.84360.9662345353574398281.stgit@manet.1015granger.net> In-Reply-To: <165643915086.84360.2809940286726976517.stgit@manet.1015granger.net> References: <165643915086.84360.2809940286726976517.stgit@manet.1015granger.net> User-Agent: StGit/1.5.dev2+g9ce680a5 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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 Reported-by: Wang Yugui Link: https://bugzilla.linux-nfs.org/show_bug.cgi?id=386 Suggested-by: Trond Myklebust Signed-off-by: Chuck Lever --- 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 37373b012276..6e9e186334ab 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -269,6 +269,7 @@ 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); } @@ -298,7 +299,6 @@ 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; @@ -319,6 +319,7 @@ 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; } @@ -330,6 +331,7 @@ 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); } } @@ -339,7 +341,7 @@ 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); @@ -439,8 +441,18 @@ 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, @@ -462,8 +474,9 @@ 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; } /* @@ -1020,6 +1033,7 @@ 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); if (!(may_flags & NFSD_MAY_NOT_BREAK_LEASE)) { @@ -1055,7 +1069,6 @@ 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, @@ -1080,6 +1093,7 @@ 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 16094ddbf35a..ff14e2182de5 100644 --- a/fs/nfsd/trace.h +++ b/fs/nfsd/trace.h @@ -883,7 +883,9 @@ 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);