From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qg0-f42.google.com (mail-qg0-f42.google.com [209.85.192.42]) by kanga.kvack.org (Postfix) with ESMTP id B4AD46B0072 for ; Thu, 28 May 2015 14:51:11 -0400 (EDT) Received: by qgfa63 with SMTP id a63so20535119qgf.0 for ; Thu, 28 May 2015 11:51:11 -0700 (PDT) Received: from mail-qk0-x233.google.com (mail-qk0-x233.google.com. [2607:f8b0:400d:c09::233]) by mx.google.com with ESMTPS id l2si3255615qkh.113.2015.05.28.11.51.11 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 28 May 2015 11:51:11 -0700 (PDT) Received: by qkhg32 with SMTP id g32so31835922qkh.0 for ; Thu, 28 May 2015 11:51:11 -0700 (PDT) From: Tejun Heo Subject: [PATCH 6/9] writeback: use unlocked_inode_to_wb transaction in inode_congested() Date: Thu, 28 May 2015 14:50:54 -0400 Message-Id: <1432839057-17609-7-git-send-email-tj@kernel.org> In-Reply-To: <1432839057-17609-1-git-send-email-tj@kernel.org> References: <1432839057-17609-1-git-send-email-tj@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: axboe@kernel.dk Cc: linux-kernel@vger.kernel.org, jack@suse.cz, hch@infradead.org, hannes@cmpxchg.org, linux-fsdevel@vger.kernel.org, vgoyal@redhat.com, lizefan@huawei.com, cgroups@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.cz, clm@fb.com, fengguang.wu@intel.com, david@fromorbit.com, gthelen@google.com, khlebnikov@yandex-team.ru, Tejun Heo Similar to wb stat updates, inode_congested() accesses the associated wb of an inode locklessly, which will break with foreign inode wb switching. This path updates inode_congested() to use unlocked inode wb access transaction introduced by the previous patch. Combined with the previous two patches, this makes all wb list and access operations to be protected by either of inode->i_lock, wb->list_lock, or mapping->tree_lock while wb switching is in progress. Signed-off-by: Tejun Heo Cc: Jens Axboe Cc: Jan Kara Cc: Wu Fengguang Cc: Greg Thelen --- fs/fs-writeback.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 08f5496..25458fa 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -618,10 +618,18 @@ void wbc_account_io(struct writeback_control *wbc, struct page *page, */ int inode_congested(struct inode *inode, int cong_bits) { - if (inode) { - struct bdi_writeback *wb = inode_to_wb(inode); - if (wb) - return wb_congested(wb, cong_bits); + /* + * Once set, ->i_wb never becomes NULL while the inode is alive. + * Start transaction iff ->i_wb is visible. + */ + if (inode && inode_to_wb(inode)) { + struct bdi_writeback *wb; + bool locked, congested; + + wb = unlocked_inode_to_wb_begin(inode, &locked); + congested = wb_congested(wb, cong_bits); + unlocked_inode_to_wb_end(inode, locked); + return congested; } return wb_congested(&inode_to_bdi(inode)->wb, cong_bits); -- 2.4.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org