Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail-ie0-f178.google.com ([209.85.223.178]:35873 "EHLO mail-ie0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752663AbaHHPBL (ORCPT ); Fri, 8 Aug 2014 11:01:11 -0400 Received: by mail-ie0-f178.google.com with SMTP id rd18so6533789iec.9 for ; Fri, 08 Aug 2014 08:01:10 -0700 (PDT) From: Weston Andros Adamson To: trond.myklebust@primarydata.com Cc: linux-nfs@vger.kernel.org, Weston Andros Adamson Subject: [PATCH 2/5] nfs: fix nonblocking calls to nfs_page_group_lock Date: Fri, 8 Aug 2014 11:00:54 -0400 Message-Id: <1407510057-6881-3-git-send-email-dros@primarydata.com> In-Reply-To: <1407510057-6881-1-git-send-email-dros@primarydata.com> References: <1407510057-6881-1-git-send-email-dros@primarydata.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: nfs_page_group_lock was calling wait_on_bit_lock even when told not to block. Fix by first trying test_and_set_bit, followed by wait_on_bit_lock if and only if blocking is allowed. Return -EAGAIN if nonblocking and the test_and_set of the bit was already locked. Signed-off-by: Weston Andros Adamson Reviewed-by: Peng Tao --- fs/nfs/pagelist.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c index 38eaf83..f393c72 100644 --- a/fs/nfs/pagelist.c +++ b/fs/nfs/pagelist.c @@ -149,24 +149,29 @@ static int nfs_wait_bit_uninterruptible(void *word) * * this lock must be held if modifying the page group list * - * returns result from wait_on_bit_lock: 0 on success, < 0 on error + * return 0 on success, < 0 on error: -EDELAY if nonblocking or the + * result from wait_on_bit_lock + * + * NOTE: calling with nonblock=false should always have set the + * lock bit (see fs/buffer.c and other uses of wait_on_bit_lock + * with TASK_UNINTERRUPTIBLE), so there is no need to check the result. */ int nfs_page_group_lock(struct nfs_page *req, bool nonblock) { struct nfs_page *head = req->wb_head; - int ret; WARN_ON_ONCE(head != head->wb_head); - do { - ret = wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK, - nfs_wait_bit_uninterruptible, - TASK_UNINTERRUPTIBLE); - } while (!nonblock && ret != 0); + if (!test_and_set_bit(PG_HEADLOCK, &head->wb_flags)) + return 0; - WARN_ON_ONCE(ret > 0); - return ret; + if (!nonblock) + return wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK, + nfs_wait_bit_uninterruptible, + TASK_UNINTERRUPTIBLE); + + return -EAGAIN; } /* -- 1.8.5.2 (Apple Git-48)