Return-Path: linux-nfs-owner@vger.kernel.org Received: from casper.infradead.org ([85.118.1.10]:57922 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753473AbbANJoF (ORCPT ); Wed, 14 Jan 2015 04:44:05 -0500 From: Christoph Hellwig To: Jens Axboe Cc: David Howells , Tejun Heo , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-mtd@lists.infradead.org, linux-nfs@vger.kernel.org, ceph-devel@vger.kernel.org Subject: [PATCH 11/12] fs: don't reassign dirty inodes to default_backing_dev_info Date: Wed, 14 Jan 2015 10:42:40 +0100 Message-Id: <1421228561-16857-12-git-send-email-hch@lst.de> In-Reply-To: <1421228561-16857-1-git-send-email-hch@lst.de> References: <1421228561-16857-1-git-send-email-hch@lst.de> Sender: linux-nfs-owner@vger.kernel.org List-ID: If we have dirty inodes we need to call the filesystem for it, even if the device has been removed and the filesystem will error out early. The current code does that by reassining all dirty inodes to the default backing_dev_info when a bdi is unlinked, but that's pretty pointless given that the bdi must always outlive the super block. Instead of stopping writeback at unregister time and moving inodes to the default bdi just keep the current bdi alive until it is destroyed. The containing objects of the bdi ensure this doesn't happen until all writeback has finished by erroring out. Signed-off-by: Christoph Hellwig Reviewed-by: Tejun Heo --- mm/backing-dev.c | 91 +++++++++++++++----------------------------------------- 1 file changed, 24 insertions(+), 67 deletions(-) diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 52e0c76..3ebba25 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -37,17 +37,6 @@ LIST_HEAD(bdi_list); /* bdi_wq serves all asynchronous writeback tasks */ struct workqueue_struct *bdi_wq; -static void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2) -{ - if (wb1 < wb2) { - spin_lock(&wb1->list_lock); - spin_lock_nested(&wb2->list_lock, 1); - } else { - spin_lock(&wb2->list_lock); - spin_lock_nested(&wb1->list_lock, 1); - } -} - #ifdef CONFIG_DEBUG_FS #include #include @@ -352,19 +341,19 @@ EXPORT_SYMBOL(bdi_register_dev); */ static void bdi_wb_shutdown(struct backing_dev_info *bdi) { - if (!bdi_cap_writeback_dirty(bdi)) + /* Make sure nobody queues further work */ + spin_lock_bh(&bdi->wb_lock); + if (!test_and_clear_bit(BDI_registered, &bdi->state)) { + spin_unlock_bh(&bdi->wb_lock); return; + } + spin_unlock_bh(&bdi->wb_lock); /* * Make sure nobody finds us on the bdi_list anymore */ bdi_remove_from_list(bdi); - /* Make sure nobody queues further work */ - spin_lock_bh(&bdi->wb_lock); - clear_bit(BDI_registered, &bdi->state); - spin_unlock_bh(&bdi->wb_lock); - /* * Drain work list and shutdown the delayed_work. At this point, * @bdi->bdi_list is empty telling bdi_Writeback_workfn() that @bdi @@ -372,37 +361,22 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi) */ mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0); flush_delayed_work(&bdi->wb.dwork); - WARN_ON(!list_empty(&bdi->work_list)); - WARN_ON(delayed_work_pending(&bdi->wb.dwork)); } /* - * This bdi is going away now, make sure that no super_blocks point to it + * Called when the device behind @bdi has been removed or ejected. + * + * We can't really do much here except for reducing the dirty ratio at + * the moment. In the future we should be able to set a flag so that + * the filesystem can handle errors at mark_inode_dirty time instead + * of only at writeback time. */ -static void bdi_prune_sb(struct backing_dev_info *bdi) -{ - struct super_block *sb; - - spin_lock(&sb_lock); - list_for_each_entry(sb, &super_blocks, s_list) { - if (sb->s_bdi == bdi) - sb->s_bdi = &default_backing_dev_info; - } - spin_unlock(&sb_lock); -} - void bdi_unregister(struct backing_dev_info *bdi) { - if (bdi->dev) { - bdi_set_min_ratio(bdi, 0); - trace_writeback_bdi_unregister(bdi); - bdi_prune_sb(bdi); + if (WARN_ON_ONCE(!bdi->dev)) + return; - bdi_wb_shutdown(bdi); - bdi_debug_unregister(bdi); - device_unregister(bdi->dev); - bdi->dev = NULL; - } + bdi_set_min_ratio(bdi, 0); } EXPORT_SYMBOL(bdi_unregister); @@ -471,37 +445,20 @@ void bdi_destroy(struct backing_dev_info *bdi) { int i; - /* - * Splice our entries to the default_backing_dev_info. This - * condition shouldn't happen. @wb must be empty at this point and - * dirty inodes on it might cause other issues. This workaround is - * added by ce5f8e779519 ("writeback: splice dirty inode entries to - * default bdi on bdi_destroy()") without root-causing the issue. - * - * http://lkml.kernel.org/g/1253038617-30204-11-git-send-email-jens.axboe@oracle.com - * http://thread.gmane.org/gmane.linux.file-systems/35341/focus=35350 - * - * We should probably add WARN_ON() to find out whether it still - * happens and track it down if so. - */ - if (bdi_has_dirty_io(bdi)) { - struct bdi_writeback *dst = &default_backing_dev_info.wb; - - bdi_lock_two(&bdi->wb, dst); - list_splice(&bdi->wb.b_dirty, &dst->b_dirty); - list_splice(&bdi->wb.b_io, &dst->b_io); - list_splice(&bdi->wb.b_more_io, &dst->b_more_io); - spin_unlock(&bdi->wb.list_lock); - spin_unlock(&dst->list_lock); - } - - bdi_unregister(bdi); + bdi_wb_shutdown(bdi); + WARN_ON(!list_empty(&bdi->work_list)); + WARN_ON(delayed_work_pending(&bdi->wb.dwork)); WARN_ON(delayed_work_pending(&bdi->wb.dwork)); + if (bdi->dev) { + bdi_debug_unregister(bdi); + device_unregister(bdi->dev); + bdi->dev = NULL; + } + for (i = 0; i < NR_BDI_STAT_ITEMS; i++) percpu_counter_destroy(&bdi->bdi_stat[i]); - fprop_local_destroy_percpu(&bdi->completions); } EXPORT_SYMBOL(bdi_destroy); -- 1.9.1