From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:55913 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753087AbbLISkd (ORCPT ); Wed, 9 Dec 2015 13:40:33 -0500 Date: Wed, 9 Dec 2015 13:40:30 -0500 From: Brian Foster To: Josef Bacik Cc: linux-fsdevel@vger.kernel.org, kernel-team@fb.com, viro@ZenIV.linux.org.uk, hch@infradead.org, david@fromorbit.com, jack@suse.cz, Dave Chinner Subject: Re: [PATCH 6/8] bdi: add a new writeback list for sync Message-ID: <20151209184030.GD45171@bfoster.bfoster> References: <1435116242-27495-1-git-send-email-jbacik@fb.com> <1435116242-27495-7-git-send-email-jbacik@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1435116242-27495-7-git-send-email-jbacik@fb.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, Jun 23, 2015 at 08:24:00PM -0700, Josef Bacik wrote: > From: Dave Chinner > > wait_sb_inodes() current does a walk of all inodes in the filesystem > to find dirty one to wait on during sync. This is highly > inefficient and wastes a lot of CPU when there are lots of clean > cached inodes that we don't need to wait on. > > To avoid this "all inode" walk, we need to track inodes that are > currently under writeback that we need to wait for. We do this by > adding inodes to a writeback list on the bdi when the mapping is > first tagged as having pages under writeback. wait_sb_inodes() can > then walk this list of "inodes under IO" and wait specifically just > for the inodes that the current sync(2) needs to wait for. > > To avoid needing all the realted locking to be safe against > interrupts, Jan Kara suggested that we be lazy about removal from > the writeback list. That is, we don't remove inodes from the > writeback list on IO completion, but do it directly during a > wait_sb_inodes() walk. > > This means that the a rare sync(2) call will have some work to do > skipping clean inodes However, in the current problem case of > concurrent sync workloads, concurrent wait_sb_inodes() calls only > walk the very recently dispatched inodes and hence should have very > little work to do. > > This also means that we have to remove the inodes from the writeback > list during eviction. Do this in inode_wait_for_writeback() once > all writeback on the inode is complete. > > Signed-off-by: Dave Chinner > Signed-off-by: Josef Bacik > Tested-by: Dave Chinner > Reviewed-by: Jan Kara > --- Hi all, My understanding is this (and the subsequent) patch were never merged due to conflicts with the cgroup aware writeback stuff that had been merged. I think the fundamental approach of this patch still solves the original problem, the writeback inodes are just always tracked on the root bdi_writeback rather than the per-cgroup bdi_writeback the inode was associated with before writeback. Any thoughts on that are appreciated. Otherwise, I'm trying to rebase this and I've hit a lockdep splat [1] that suggests the locking for the writeback list needs to be tweaked one way or another. Note that lockdep fires with this original version as well, so I don't think this is a new issue. I _think_ this means that list_lock either needs to be taken outside of mapping->tree_lock or we need to create a new irq safe spinlock specific to the b_writeback list. The former looks like it requires some ugliness in __test_set_page_writeback() to acquire list_lock first, but only when list_empty(&inode->i_wb_list) so we don't grab it for every page. The latter obviously means a new irq-disabling lock (which is already done in parts of wait_sb_inode(), fwiw). The latter might also facilitate further cleanups like pulling b_writeback out of bdi_writeback and up into backing_dev_info since we really only need one instance of the list, but I'm not sure if that's preferable.. Thoughts? Brian [1] lockdep splat: [ INFO: possible irq lock inversion dependency detected ] 4.4.0-rc4+ #54 Not tainted --------------------------------------------------------- swapper/0/0 just changed the state of lock: (&(&mapping->tree_lock)->rlock){-.....}, at: [] test_clear_page_writeback+0x5d/0x210 but this lock took another, HARDIRQ-unsafe lock in the past: (&(&wb->list_lock)->rlock){+.+...}#012#012and interrupts could create inverse lock ordering between them. #012other info that might help us debug this: Possible interrupt unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&(&wb->list_lock)->rlock); local_irq_disable(); lock(&(&mapping->tree_lock)->rlock); lock(&(&wb->list_lock)->rlock); lock(&(&mapping->tree_lock)->rlock); #012 *** DEADLOCK *** no locks held by swapper/0/0. #012the shortest dependencies between 2nd lock and 1st lock: -> (&(&wb->list_lock)->rlock){+.+...} ops: 194 { HARDIRQ-ON-W at: [] __lock_acquire+0x819/0x1a50 [] lock_acquire+0xce/0x1c0 [] _raw_spin_lock+0x38/0x50 [] __mark_inode_dirty+0x3d9/0x5e0 [] generic_update_time+0x79/0xd0 [] touch_atime+0xa8/0xd0 [] iterate_dir+0xe3/0x130 [] SyS_getdents+0x9d/0x130 [] entry_SYSCALL_64_fastpath+0x12/0x76 SOFTIRQ-ON-W at: [] __lock_acquire+0x84a/0x1a50 [] lock_acquire+0xce/0x1c0 [] _raw_spin_lock+0x38/0x50 [] __mark_inode_dirty+0x3d9/0x5e0 [] generic_update_time+0x79/0xd0 [] touch_atime+0xa8/0xd0 [] iterate_dir+0xe3/0x130 [] SyS_getdents+0x9d/0x130 [] entry_SYSCALL_64_fastpath+0x12/0x76 INITIAL USE at: [] __lock_acquire+0x3f8/0x1a50 [] lock_acquire+0xce/0x1c0 [] _raw_spin_lock+0x38/0x50 [] __mark_inode_dirty+0x3d9/0x5e0 [] generic_update_time+0x79/0xd0 [] touch_atime+0xa8/0xd0 [] iterate_dir+0xe3/0x130 [] SyS_getdents+0x9d/0x130 [] entry_SYSCALL_64_fastpath+0x12/0x76 } ... key at: [] __key.37388+0x0/0x8 ... acquired at: [] lock_acquire+0xce/0x1c0 [] _raw_spin_lock+0x38/0x50 [] bdi_mark_inode_writeback+0x67/0xd0 [] __test_set_page_writeback+0x112/0x200 [] __block_write_full_page.constprop.44+0xec/0x400 [] block_write_full_page+0xfe/0x190 [] blkdev_writepage+0x18/0x20 [] __writepage+0x16/0x40 [] write_cache_pages+0x225/0x5f0 [] generic_writepages+0x54/0x80 [] do_writepages+0x21/0x30 [] __filemap_fdatawrite_range+0x80/0xb0 [] filemap_write_and_wait_range+0x2d/0x70 [] blkdev_fsync+0x1b/0x50 [] vfs_fsync_range+0x4b/0xb0 [] do_fsync+0x3d/0x70 [] SyS_fsync+0x10/0x20 [] entry_SYSCALL_64_fastpath+0x12/0x76 -> (&(&mapping->tree_lock)->rlock){-.....} ops: 16821 { IN-HARDIRQ-W at: [] __lock_acquire+0x999/0x1a50 [] lock_acquire+0xce/0x1c0 [] _raw_spin_lock_irqsave+0x50/0x70 [] test_clear_page_writeback+0x5d/0x210 [] end_page_writeback+0x1f/0xa0 [] end_buffer_async_write+0xd3/0x1a0 [] end_bio_bh_io_sync+0x28/0x40 [] bio_endio+0x3f/0x60 [] dec_pending+0x149/0x310 [] clone_endio+0x76/0xe0 [] bio_endio+0x3f/0x60 [] blk_update_request+0xb2/0x3a0 [] blk_mq_end_request+0x1a/0x70 [] virtblk_request_done+0x3f/0x70 [virtio_blk] [] __blk_mq_complete_request_remote+0x13/0x20 [] flush_smp_call_function_queue+0x5f/0x160 [] generic_smp_call_function_single_interrupt+0x13/0x60 [] smp_call_function_single_interrupt+0x27/0x40 [] call_function_single_interrupt+0x8c/0xa0 [] default_idle+0x23/0x150 [] arch_cpu_idle+0xf/0x20 [] default_idle_call+0x2a/0x40 [] cpu_startup_entry+0x384/0x3f0 [] rest_init+0x13a/0x140 [] start_kernel+0x49e/0x4bf [] x86_64_start_reservations+0x2a/0x2c [] x86_64_start_kernel+0x145/0x168 INITIAL USE at: [] __lock_acquire+0x3f8/0x1a50 [] lock_acquire+0xce/0x1c0 [] _raw_spin_lock_irq+0x44/0x60 [] __add_to_page_cache_locked+0xbc/0x340 [] add_to_page_cache_lru+0x37/0x90 [] pagecache_get_page+0xb7/0x200 [] grab_cache_page_write_begin+0x29/0x40 [] simple_write_begin+0x28/0x1c0 [] generic_perform_write+0xd1/0x1e0 [] __generic_file_write_iter+0x1a2/0x1e0 [] generic_file_write_iter+0xe8/0x1e0 [] __vfs_write+0xc9/0x110 [] vfs_write+0xa9/0x1a0 [] SyS_write+0x58/0xd0 [] xwrite+0x29/0x5c [] do_copy+0x2a/0xb8 [] write_buffer+0x23/0x34 [] unpack_to_rootfs+0xfd/0x294 [] populate_rootfs+0x5c/0x108 [] do_one_initcall+0xb3/0x200 [] kernel_init_freeable+0x1ee/0x28d [] kernel_init+0xe/0xe0 [] ret_from_fork+0x3f/0x70 } ... key at: [] __key.39560+0x0/0x8 ... acquired at: [] check_usage_forwards+0x15b/0x160 [] mark_lock+0x333/0x610 [] __lock_acquire+0x999/0x1a50 [] lock_acquire+0xce/0x1c0 [] _raw_spin_lock_irqsave+0x50/0x70 [] test_clear_page_writeback+0x5d/0x210 [] end_page_writeback+0x1f/0xa0 [] end_buffer_async_write+0xd3/0x1a0 [] end_bio_bh_io_sync+0x28/0x40 [] bio_endio+0x3f/0x60 [] dec_pending+0x149/0x310 [] clone_endio+0x76/0xe0 [] bio_endio+0x3f/0x60 [] blk_update_request+0xb2/0x3a0 [] blk_mq_end_request+0x1a/0x70 [] virtblk_request_done+0x3f/0x70 [virtio_blk] [] __blk_mq_complete_request_remote+0x13/0x20 [] flush_smp_call_function_queue+0x5f/0x160 [] generic_smp_call_function_single_interrupt+0x13/0x60 [] smp_call_function_single_interrupt+0x27/0x40 [] call_function_single_interrupt+0x8c/0xa0 [] default_idle+0x23/0x150 [] arch_cpu_idle+0xf/0x20 [] default_idle_call+0x2a/0x40 [] cpu_startup_entry+0x384/0x3f0 [] rest_init+0x13a/0x140 [] start_kernel+0x49e/0x4bf [] x86_64_start_reservations+0x2a/0x2c [] x86_64_start_kernel+0x145/0x168 #012stack backtrace: CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.0-rc4+ #54 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 0000000000000000 06776aa479e380f6 ffff88011fc03ad0 ffffffff813dd019 ffffffff82a0f120 ffff88011fc03b10 ffffffff811c184d ffffffff81c10be8 ffffffff81c10be8 ffffffff81c10500 ffffffff81a56510 0000000000000000 Call Trace: [] dump_stack+0x4b/0x72 [] print_irq_inversion_bug.part.38+0x1a4/0x1b0 [] check_usage_forwards+0x15b/0x160 [] mark_lock+0x333/0x610 [] ? check_usage_backwards+0x160/0x160 [] __lock_acquire+0x999/0x1a50 [] lock_acquire+0xce/0x1c0 [] ? test_clear_page_writeback+0x5d/0x210 [] _raw_spin_lock_irqsave+0x50/0x70 [] ? test_clear_page_writeback+0x5d/0x210 [] test_clear_page_writeback+0x5d/0x210 [] end_page_writeback+0x1f/0xa0 [] end_buffer_async_write+0xd3/0x1a0 [] end_bio_bh_io_sync+0x28/0x40 [] bio_endio+0x3f/0x60 [] dec_pending+0x149/0x310 [] ? mempool_free+0x29/0x80 [] clone_endio+0x76/0xe0 [] bio_endio+0x3f/0x60 [] blk_update_request+0xb2/0x3a0 [] ? blkdev_issue_zeroout+0xf0/0xf0 [] blk_mq_end_request+0x1a/0x70 [] virtblk_request_done+0x3f/0x70 [virtio_blk] [] __blk_mq_complete_request_remote+0x13/0x20 [] flush_smp_call_function_queue+0x5f/0x160 [] generic_smp_call_function_single_interrupt+0x13/0x60 [] smp_call_function_single_interrupt+0x27/0x40 [] call_function_single_interrupt+0x8c/0xa0 [] ? native_safe_halt+0x6/0x10 [] default_idle+0x23/0x150 [] arch_cpu_idle+0xf/0x20 [] default_idle_call+0x2a/0x40 [] cpu_startup_entry+0x384/0x3f0 [] rest_init+0x13a/0x140 [] start_kernel+0x49e/0x4bf [] ? early_idt_handler_array+0x120/0x120 [] x86_64_start_reservations+0x2a/0x2c [] x86_64_start_kernel+0x145/0x168 > fs/block_dev.c | 2 + > fs/fs-writeback.c | 148 +++++++++++++++++++++++++++++++++++--------- > fs/inode.c | 1 + > include/linux/backing-dev.h | 5 ++ > include/linux/fs.h | 1 + > mm/backing-dev.c | 1 + > mm/page-writeback.c | 14 +++++ > 7 files changed, 144 insertions(+), 28 deletions(-) > > diff --git a/fs/block_dev.c b/fs/block_dev.c > index f2a89be..2726ff1 100644 > --- a/fs/block_dev.c > +++ b/fs/block_dev.c > @@ -64,6 +64,8 @@ void kill_bdev(struct block_device *bdev) > { > struct address_space *mapping = bdev->bd_inode->i_mapping; > > + bdi_clear_inode_writeback(inode_to_bdi(bdev->bd_inode), > + bdev->bd_inode); > if (mapping->nrpages == 0 && mapping->nrshadows == 0) > return; > > diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c > index aa72536..5c005ad 100644 > --- a/fs/fs-writeback.c > +++ b/fs/fs-writeback.c > @@ -210,6 +210,34 @@ void inode_wb_list_del(struct inode *inode) > } > > /* > + * mark an inode as under writeback on the given bdi > + */ > +void bdi_mark_inode_writeback(struct backing_dev_info *bdi, struct inode *inode) > +{ > + WARN_ON_ONCE(bdi != inode_to_bdi(inode)); > + if (list_empty(&inode->i_wb_list)) { > + spin_lock(&bdi->wb.list_lock); > + if (list_empty(&inode->i_wb_list)) > + list_add_tail(&inode->i_wb_list, &bdi->wb.b_writeback); > + spin_unlock(&bdi->wb.list_lock); > + } > +} > + > +/* > + * clear an inode as under writeback on the given bdi > + */ > +void bdi_clear_inode_writeback(struct backing_dev_info *bdi, > + struct inode *inode) > +{ > + WARN_ON_ONCE(bdi != inode_to_bdi(inode)); > + if (!list_empty(&inode->i_wb_list)) { > + spin_lock(&bdi->wb.list_lock); > + list_del_init(&inode->i_wb_list); > + spin_unlock(&bdi->wb.list_lock); > + } > +} > + > +/* > * Redirty an inode: set its when-it-was dirtied timestamp and move it to the > * furthest end of its superblock's dirty-inode list. > * > @@ -383,13 +411,28 @@ static void __inode_wait_for_writeback(struct inode *inode) > } > > /* > - * Wait for writeback on an inode to complete. Caller must have inode pinned. > + * Wait for writeback on an inode to complete during eviction. Caller must have > + * inode pinned. > */ > void inode_wait_for_writeback(struct inode *inode) > { > + BUG_ON(!(inode->i_state & I_FREEING)); > + > spin_lock(&inode->i_lock); > __inode_wait_for_writeback(inode); > spin_unlock(&inode->i_lock); > + > + /* > + * For a bd_inode when we do inode_to_bdi we'll want to get the bdev for > + * the inode and then deref bdev->bd_disk, which at this point has been > + * set to NULL, so we would panic. At the point we are dropping our > + * bd_inode we won't have any pages under writeback on the device so > + * this is safe. But just in case we'll assert to make sure we don't > + * screw this up. > + */ > + if (!sb_is_blkdev_sb(inode->i_sb)) > + bdi_clear_inode_writeback(inode_to_bdi(inode), inode); > + BUG_ON(!list_empty(&inode->i_wb_list)); > } > > /* > @@ -1372,7 +1415,9 @@ EXPORT_SYMBOL(__mark_inode_dirty); > */ > static void wait_sb_inodes(struct super_block *sb) > { > - struct inode *inode, *old_inode = NULL; > + struct backing_dev_info *bdi = sb->s_bdi; > + LIST_HEAD(sync_list); > + struct inode *iput_inode = NULL; > > /* > * We need to be protected against the filesystem going from > @@ -1380,48 +1425,95 @@ static void wait_sb_inodes(struct super_block *sb) > */ > WARN_ON(!rwsem_is_locked(&sb->s_umount)); > > - mutex_lock(&sb->s_sync_lock); > - spin_lock(&sb->s_inode_list_lock); > - > /* > - * Data integrity sync. Must wait for all pages under writeback, > - * because there may have been pages dirtied before our sync > - * call, but which had writeout started before we write it out. > - * In which case, the inode may not be on the dirty list, but > - * we still have to wait for that writeout. > + * Data integrity sync. Must wait for all pages under writeback, because > + * there may have been pages dirtied before our sync call, but which had > + * writeout started before we write it out. In which case, the inode > + * may not be on the dirty list, but we still have to wait for that > + * writeout. > + * > + * To avoid syncing inodes put under IO after we have started here, > + * splice the io list to a temporary list head and walk that. Newly > + * dirtied inodes will go onto the primary list so we won't wait for > + * them. This is safe to do as we are serialised by the s_sync_lock, > + * so we'll complete processing the complete list before the next > + * sync operation repeats the splice-and-walk process. > + * > + * Inodes that have pages under writeback after we've finished the wait > + * may or may not be on the primary list. They had pages under put IO > + * after we started our wait, so we need to make sure the next sync or > + * IO completion treats them correctly, Move them back to the primary > + * list and restart the walk. > + * > + * Inodes that are clean after we have waited for them don't belong on > + * any list, so simply remove them from the sync list and move onwards. > */ > - list_for_each_entry(inode, &sb->s_inodes, i_sb_list) { > + mutex_lock(&sb->s_sync_lock); > + spin_lock(&bdi->wb.list_lock); > + list_splice_init(&bdi->wb.b_writeback, &sync_list); > + > + while (!list_empty(&sync_list)) { > + struct inode *inode = list_first_entry(&sync_list, struct inode, > + i_wb_list); > struct address_space *mapping = inode->i_mapping; > > + /* > + * We are lazy on IO completion and don't remove inodes from the > + * list when they are clean. Detect that immediately and skip > + * inodes we don't ahve to wait on. > + */ > + if (!mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK)) { > + list_del_init(&inode->i_wb_list); > + cond_resched_lock(&bdi->wb.list_lock); > + continue; > + } > + > spin_lock(&inode->i_lock); > - if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) || > - (mapping->nrpages == 0)) { > + if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) { > + list_move(&inode->i_wb_list, &bdi->wb.b_writeback); > spin_unlock(&inode->i_lock); > + cond_resched_lock(&bdi->wb.list_lock); > continue; > } > __iget(inode); > spin_unlock(&inode->i_lock); > - spin_unlock(&sb->s_inode_list_lock); > + spin_unlock(&bdi->wb.list_lock); > > - /* > - * We hold a reference to 'inode' so it couldn't have been > - * removed from s_inodes list while we dropped the > - * s_inode_list_lock. We cannot iput the inode now as we can > - * be holding the last reference and we cannot iput it under > - * s_inode_list_lock. So we keep the reference and iput it > - * later. > - */ > - iput(old_inode); > - old_inode = inode; > + if (iput_inode) > + iput(iput_inode); > > filemap_fdatawait(mapping); > - > cond_resched(); > > - spin_lock(&sb->s_inode_list_lock); > + /* > + * the inode has been written back now, so check whether we > + * still have pages under IO and move it back to the primary > + * list if necessary. We really need the mapping->tree_lock > + * here because bdi_mark_inode_writeback may have not done > + * anything because we were on the spliced list and we need to > + * check TAG_WRITEBACK. > + */ > + spin_lock_irq(&mapping->tree_lock); > + spin_lock(&bdi->wb.list_lock); > + if (mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK)) { > + WARN_ON(list_empty(&inode->i_wb_list)); > + list_move(&inode->i_wb_list, &bdi->wb.b_writeback); > + } else > + list_del_init(&inode->i_wb_list); > + spin_unlock_irq(&mapping->tree_lock); > + > + /* > + * can't iput inode while holding the wb.list_lock. Save it for > + * the next time through the loop when we drop all our spin > + * locks. > + */ > + iput_inode = inode; > } > - spin_unlock(&sb->s_inode_list_lock); > - iput(old_inode); > + spin_unlock(&bdi->wb.list_lock); > + > + if (iput_inode) > + iput(iput_inode); > + > mutex_unlock(&sb->s_sync_lock); > } > > diff --git a/fs/inode.c b/fs/inode.c > index 770d684..8f00557 100644 > --- a/fs/inode.c > +++ b/fs/inode.c > @@ -357,6 +357,7 @@ void inode_init_once(struct inode *inode) > INIT_HLIST_NODE(&inode->i_hash); > INIT_LIST_HEAD(&inode->i_devices); > INIT_LIST_HEAD(&inode->i_io_list); > + INIT_LIST_HEAD(&inode->i_wb_list); > INIT_LIST_HEAD(&inode->i_lru); > address_space_init_once(&inode->i_data); > i_size_ordered_init(inode); > diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h > index d87d8ec..0d5bca2 100644 > --- a/include/linux/backing-dev.h > +++ b/include/linux/backing-dev.h > @@ -56,6 +56,7 @@ struct bdi_writeback { > struct list_head b_io; /* parked for writeback */ > struct list_head b_more_io; /* parked for more writeback */ > struct list_head b_dirty_time; /* time stamps are dirty */ > + struct list_head b_writeback; /* inodes under writeback */ > spinlock_t list_lock; /* protects the b_* lists */ > }; > > @@ -123,6 +124,10 @@ void bdi_start_background_writeback(struct backing_dev_info *bdi); > void bdi_writeback_workfn(struct work_struct *work); > int bdi_has_dirty_io(struct backing_dev_info *bdi); > void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi); > +void bdi_mark_inode_writeback(struct backing_dev_info *bdi, > + struct inode *inode); > +void bdi_clear_inode_writeback(struct backing_dev_info *bdi, > + struct inode *inode); > > extern spinlock_t bdi_lock; > extern struct list_head bdi_list; > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 6dd2ab2..d3baa08 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -636,6 +636,7 @@ struct inode { > struct list_head i_io_list; /* backing dev IO list */ > struct list_head i_lru; /* inode LRU list */ > struct list_head i_sb_list; > + struct list_head i_wb_list; /* backing dev writeback list */ > union { > struct hlist_head i_dentry; > struct rcu_head i_rcu; > diff --git a/mm/backing-dev.c b/mm/backing-dev.c > index e9ed047..ea39301 100644 > --- a/mm/backing-dev.c > +++ b/mm/backing-dev.c > @@ -369,6 +369,7 @@ static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi) > INIT_LIST_HEAD(&wb->b_io); > INIT_LIST_HEAD(&wb->b_more_io); > INIT_LIST_HEAD(&wb->b_dirty_time); > + INIT_LIST_HEAD(&wb->b_writeback); > spin_lock_init(&wb->list_lock); > INIT_DELAYED_WORK(&wb->dwork, bdi_writeback_workfn); > } > diff --git a/mm/page-writeback.c b/mm/page-writeback.c > index eb59f7e..f3751d1 100644 > --- a/mm/page-writeback.c > +++ b/mm/page-writeback.c > @@ -2382,11 +2382,25 @@ int __test_set_page_writeback(struct page *page, bool keep_write) > spin_lock_irqsave(&mapping->tree_lock, flags); > ret = TestSetPageWriteback(page); > if (!ret) { > + bool on_wblist; > + > + on_wblist = mapping_tagged(mapping, > + PAGECACHE_TAG_WRITEBACK); > + > radix_tree_tag_set(&mapping->page_tree, > page_index(page), > PAGECACHE_TAG_WRITEBACK); > if (bdi_cap_account_writeback(bdi)) > __inc_bdi_stat(bdi, BDI_WRITEBACK); > + > + /* > + * we can come through here when swapping anonymous > + * pages, so we don't necessarily have an inode to > + * track for sync. Inodes are remove lazily, so there is > + * no equivalent in test_clear_page_writeback(). > + */ > + if (!on_wblist && mapping->host) > + bdi_mark_inode_writeback(bdi, mapping->host); > } > if (!PageDirty(page)) > radix_tree_tag_clear(&mapping->page_tree, > -- > 2.1.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html