From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: [PATCH 3/3] writeback: fix false positive WARN in __mark_inode_dirty From: Dan Williams Date: Tue, 01 Dec 2015 15:58:52 -0800 Message-ID: <20151201235852.36836.87208.stgit@dwillia2-desk3.jf.intel.com> In-Reply-To: <20151201235836.36836.90416.stgit@dwillia2-desk3.jf.intel.com> References: <20151201235836.36836.90416.stgit@dwillia2-desk3.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org To: linux-fsdevel@vger.kernel.org Cc: linux-block@vger.kernel.org, linux-nvdimm@lists.01.org, Dave Chinner , Jens Axboe , Jan Kara , Tejun Heo List-ID: This warning was added as a debugging aid way back in commit 500b067c5e6c "writeback: check for registered bdi in flusher add and inode dirty" when we were switching over to per-bdi writeback. Once the block device has been torn down it's no longer useful to complain about unregistered bdi's. Clear the writeback capability under the the wb->list_lock(), so that __mark_inode_dirty has no opportunity to race bdi_unregister() to this WARN() condition. Alternatively we could just delete the warning... Found this while testing block device remove from underneath an active fs triggering traces like: WARNING: CPU: 6 PID: 2129 at fs/fs-writeback.c:2065 __mark_inode_dirty+0x261/0x350() bdi-block not registered [..] Call Trace: [] dump_stack+0x44/0x62 [] warn_slowpath_common+0x82/0xc0 [] warn_slowpath_fmt+0x5c/0x80 [] __mark_inode_dirty+0x261/0x350 [] generic_update_time+0x79/0xd0 [] file_update_time+0xbd/0x110 [] ext4_dax_fault+0x68/0x110 [] __do_fault+0x4e/0xf0 [] handle_mm_fault+0x5e7/0x1b50 [] ? handle_mm_fault+0x51/0x1b50 [] __do_page_fault+0x191/0x3f0 [] trace_do_page_fault+0x4f/0x120 [] do_async_page_fault+0x1a/0xa0 [] async_page_fault+0x28/0x30 Cc: Jan Kara Cc: Tejun Heo Cc: Jens Axboe Cc: Dave Chinner Signed-off-by: Dan Williams --- mm/backing-dev.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 8ed2ffd963c5..24e61acf74a7 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -343,10 +343,17 @@ static void wb_shutdown(struct bdi_writeback *wb) { /* Make sure nobody queues further work */ spin_lock_bh(&wb->work_lock); + if (!test_and_clear_bit(WB_registered, &wb->state)) { spin_unlock_bh(&wb->work_lock); return; } + + /* tell __mark_inode_dirty that writeback is no longer possible */ + spin_lock(&wb->list_lock); + wb->bdi->capabilities |= BDI_CAP_NO_WRITEBACK; + spin_unlock(&wb->list_lock); + spin_unlock_bh(&wb->work_lock); /*