From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: [PATCH 07/10] writeback: use unlocked_inode_to_wb transaction in inode_congested() Date: Mon, 6 Apr 2015 16:18:25 -0400 Message-ID: <1428351508-8399-8-git-send-email-tj@kernel.org> References: <1428351508-8399-1-git-send-email-tj@kernel.org> 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, Tejun Heo To: axboe@kernel.dk Return-path: In-Reply-To: <1428351508-8399-1-git-send-email-tj@kernel.org> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org 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 97fb7f3..ee65ff09 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -596,10 +596,18 @@ 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); -- 2.1.0 -- 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