Return-Path: Received: from mail-io0-f194.google.com ([209.85.223.194]:34778 "EHLO mail-io0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753354AbdGSWKE (ORCPT ); Wed, 19 Jul 2017 18:10:04 -0400 Received: by mail-io0-f194.google.com with SMTP id f66so821522iof.1 for ; Wed, 19 Jul 2017 15:10:03 -0700 (PDT) From: Trond Myklebust To: Chuck Lever , linux-nfs@vger.kernel.org Subject: [PATCH 02/20] NFS: Reduce lock contention in nfs_page_find_head_request() Date: Wed, 19 Jul 2017 18:09:37 -0400 Message-Id: <20170719220955.58210-3-trond.myklebust@primarydata.com> In-Reply-To: <20170719220955.58210-2-trond.myklebust@primarydata.com> References: <20170719220955.58210-1-trond.myklebust@primarydata.com> <20170719220955.58210-2-trond.myklebust@primarydata.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: Add a lockless check for whether or not the page might be carrying an existing writeback before we grab the inode->i_lock. Reported-by: Chuck Lever Signed-off-by: Trond Myklebust --- fs/nfs/write.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/fs/nfs/write.c b/fs/nfs/write.c index 1d447e37f472..06e150c4e315 100644 --- a/fs/nfs/write.c +++ b/fs/nfs/write.c @@ -190,9 +190,11 @@ static struct nfs_page *nfs_page_find_head_request(struct page *page) struct inode *inode = page_file_mapping(page)->host; struct nfs_page *req = NULL; - spin_lock(&inode->i_lock); - req = nfs_page_find_head_request_locked(NFS_I(inode), page); - spin_unlock(&inode->i_lock); + if (PagePrivate(page) || PageSwapCache(page)) { + spin_lock(&inode->i_lock); + req = nfs_page_find_head_request_locked(NFS_I(inode), page); + spin_unlock(&inode->i_lock); + } return req; } -- 2.13.3