From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jaegeuk Kim Subject: Re: [PATCH v3] f2fs: fix to avoid data update racing between GC and DIO Date: Sat, 9 Jul 2016 09:22:58 -0700 Message-ID: <20160709162258.GA1837@jaegeuk> References: <1467866952-10863-1-git-send-email-chao@kernel.org> <20160708031916.GA94348@jaegeuk> <5f133653-face-a3ba-9fb4-cd0ac3239099@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from sog-mx-2.v43.ch3.sourceforge.com ([172.29.43.192] helo=mx.sourceforge.net) by sfs-ml-3.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1bLv21-0005Ch-Rt for linux-f2fs-devel@lists.sourceforge.net; Sat, 09 Jul 2016 16:23:05 +0000 Received: from mail.kernel.org ([198.145.29.136]) by sog-mx-2.v43.ch3.sourceforge.com with esmtps (TLSv1:AES256-SHA:256) (Exim 4.76) id 1bLv1z-00022m-Gf for linux-f2fs-devel@lists.sourceforge.net; Sat, 09 Jul 2016 16:23:05 +0000 Content-Disposition: inline In-Reply-To: <5f133653-face-a3ba-9fb4-cd0ac3239099@kernel.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net To: Chao Yu Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net On Fri, Jul 08, 2016 at 11:50:02PM +0800, Chao Yu wrote: > Hi Jaegeuk, > > On 2016/7/8 11:19, Jaegeuk Kim wrote: > > Hi Chao, > > > > Could you take a look at this in xfstests/generic/013? > > > > [ 502.480850] ====================================================== > > [ 502.480864] [ INFO: possible circular locking dependency detected ] > > [ 502.480877] 4.7.0-rc1+ #124 Tainted: G OE > > [ 502.480886] ------------------------------------------------------- > > [ 502.480897] fsstress/10729 is trying to acquire lock: > > [ 502.480906] (&sb->s_type->i_mutex_key#18){+.+.+.}, at: [] do_blockdev_direct_IO+0x1db/0x2310 > > [ 502.480948] > > [ 502.480948] but task is already holding lock: > > [ 502.480959] (&fi->dio_rwsem){.+.+.+}, at: [] f2fs_direct_IO+0xd1/0x3d0 [f2fs] > > [ 502.481003] > > [ 502.481003] which lock already depends on the new lock. > > [ 502.481003] > > [ 502.481018] > > [ 502.481018] the existing dependency chain (in reverse order) is: > > [ 502.481030] > > [ 502.481030] -> #1 (&fi->dio_rwsem){.+.+.+}: > > [ 502.481054] [] lock_acquire+0xd3/0x220 > > [ 502.481071] [] down_read+0x51/0xa0 > > [ 502.481089] [] f2fs_direct_IO+0xd1/0x3d0 [f2fs] > > [ 502.481114] [] generic_file_direct_write+0xa7/0x160 > > [ 502.481133] [] __generic_file_write_iter+0xbd/0x1e0 > > [ 502.481149] [] f2fs_file_write_iter+0xdb/0x100 [f2fs] > > [ 502.481173] [] __vfs_write+0xc8/0x140 > > [ 502.481190] [] vfs_write+0xb5/0x1b0 > > [ 502.481205] [] SyS_write+0x49/0xa0 > > [ 502.481220] [] entry_SYSCALL_64_fastpath+0x23/0xc1 > > [ 502.481236] > > [ 502.481236] -> #0 (&sb->s_type->i_mutex_key#18){+.+.+.}: > > [ 502.481264] [] __lock_acquire+0x161c/0x1940 > > [ 502.481280] [] lock_acquire+0xd3/0x220 > > [ 502.481296] [] down_write+0x5a/0xc0 > > [ 502.481312] [] do_blockdev_direct_IO+0x1db/0x2310 > > [ 502.481328] [] __blockdev_direct_IO+0x3a/0x40 > > [ 502.481344] [] f2fs_direct_IO+0x104/0x3d0 [f2fs] > > [ 502.481368] [] generic_file_read_iter+0x689/0x7e0 > > [ 502.481384] [] __vfs_read+0xc1/0x130 > > [ 502.481399] [] vfs_read+0x91/0x140 > > [ 502.481414] [] SyS_read+0x49/0xa0 > > [ 502.481429] [] entry_SYSCALL_64_fastpath+0x23/0xc1 > > [ 502.481445] > > [ 502.481445] other info that might help us debug this: > > [ 502.481445] > > [ 502.481459] Possible unsafe locking scenario: > > [ 502.481459] > > [ 502.481726] CPU0 CPU1 > > [ 502.481987] ---- ---- > > [ 502.482242] lock(&fi->dio_rwsem); > > [ 502.482501] lock(&sb->s_type->i_mutex_key#18); > > [ 502.482765] lock(&fi->dio_rwsem); > > [ 502.483025] lock(&sb->s_type->i_mutex_key#18); > > Seems we will suffer ABBA deadlock: > > writer reader > - f2fs_file_write_iter > - down_write(&inode->i_rwsem) > - __generic_file_write_iter > - generic_file_direct_write > - f2fs_direct_IO > - generic_file_read_iter > - f2fs_direct_IO > - down_read(&fi->dio_rwsem) > - __blockdev_direct_IO > - do_blockdev_direct_IO > - down_write(&inode->i_rwsem) > > - down_read(&fi->dio_rwsem) > > What about splitting dio_rwsem to rdio_rwsem/wdio_rwsem for reader/writer to > avoid deadlock? Hmm, how about inode_trylock in GC? > > Thanks, > > > [ 502.483285] > > [ 502.483285] *** DEADLOCK *** > > [ 502.483285] > > [ 502.484018] 1 lock held by fsstress/10729: > > [ 502.484262] #0: (&fi->dio_rwsem){.+.+.+}, at: [] f2fs_direct_IO+0xd1/0x3d0 [f2fs] > > > > Thanks, > > > > On Thu, Jul 07, 2016 at 12:49:12PM +0800, Chao Yu wrote: > >> From: Chao Yu > >> > >> Datas in file can be operated by GC and DIO simultaneously, so we will > >> face race case as below: > >> > >> For write case: > >> Thread A Thread B > >> - generic_file_direct_write > >> - invalidate_inode_pages2_range > >> - f2fs_direct_IO > >> - do_blockdev_direct_IO > >> - do_direct_IO > >> - get_more_blocks > >> - f2fs_gc > >> - do_garbage_collect > >> - gc_data_segment > >> - move_data_page > >> - do_write_data_page > >> migrate data block to new block address > >> - dio_bio_submit > >> update user data to old block address > >> > >> For read case: > >> Thread A Thread B > >> - generic_file_direct_write > >> - invalidate_inode_pages2_range > >> - f2fs_direct_IO > >> - do_blockdev_direct_IO > >> - do_direct_IO > >> - get_more_blocks > >> - f2fs_balance_fs > >> - f2fs_gc > >> - do_garbage_collect > >> - gc_data_segment > >> - move_data_page > >> - do_write_data_page > >> migrate data block to new block address > >> - write_checkpoint > >> - do_checkpoint > >> - clear_prefree_segments > >> - f2fs_issue_discard > >> discard old block adress > >> - dio_bio_submit > >> update user buffer from obsolete block address > >> > >> In order to fix this, for one file, we should let DIO and GC getting exclusion > >> against with each other. > >> > >> Signed-off-by: Chao Yu > >> --- > >> v3: use semaphore to avoid racing in between read dio and write dio. > >> fs/f2fs/data.c | 4 ++++ > >> fs/f2fs/f2fs.h | 1 + > >> fs/f2fs/gc.c | 13 +++++++++++++ > >> fs/f2fs/super.c | 1 + > >> 4 files changed, 19 insertions(+) > >> > >> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c > >> index b6fd5bd..19197bb 100644 > >> --- a/fs/f2fs/data.c > >> +++ b/fs/f2fs/data.c > >> @@ -1712,6 +1712,7 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter) > >> { > >> struct address_space *mapping = iocb->ki_filp->f_mapping; > >> struct inode *inode = mapping->host; > >> + struct f2fs_inode_info *fi = F2FS_I(inode); > >> size_t count = iov_iter_count(iter); > >> loff_t offset = iocb->ki_pos; > >> int err; > >> @@ -1727,7 +1728,10 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter) > >> > >> trace_f2fs_direct_IO_enter(inode, offset, count, iov_iter_rw(iter)); > >> > >> + down_read(&fi->dio_rwsem); > >> err = blockdev_direct_IO(iocb, inode, iter, get_data_block_dio); > >> + up_read(&fi->dio_rwsem); > >> + > >> if (iov_iter_rw(iter) == WRITE) { > >> if (err > 0) > >> set_inode_flag(inode, FI_UPDATE_WRITE); > >> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h > >> index bf9a13a..2e439ec 100644 > >> --- a/fs/f2fs/f2fs.h > >> +++ b/fs/f2fs/f2fs.h > >> @@ -474,6 +474,7 @@ struct f2fs_inode_info { > >> struct list_head inmem_pages; /* inmemory pages managed by f2fs */ > >> struct mutex inmem_lock; /* lock for inmemory pages */ > >> struct extent_tree *extent_tree; /* cached extent_tree entry */ > >> + struct rw_semaphore dio_rwsem; /* avoid racing between dio and gc */ > >> }; > >> > >> static inline void get_extent_info(struct extent_info *ext, > >> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c > >> index c612137..a9bfb8d 100644 > >> --- a/fs/f2fs/gc.c > >> +++ b/fs/f2fs/gc.c > >> @@ -755,12 +755,25 @@ next_step: > >> /* phase 3 */ > >> inode = find_gc_inode(gc_list, dni.ino); > >> if (inode) { > >> + struct f2fs_inode_info *fi = F2FS_I(inode); > >> + bool locked = false; > >> + > >> + if (S_ISREG(inode->i_mode)) { > >> + if (!down_write_trylock(&fi->dio_rwsem)) > >> + continue; > >> + locked = true; > >> + } > >> + > >> start_bidx = start_bidx_of_node(nofs, inode) > >> + ofs_in_node; > >> if (f2fs_encrypted_inode(inode) && S_ISREG(inode->i_mode)) > >> move_encrypted_block(inode, start_bidx); > >> else > >> move_data_page(inode, start_bidx, gc_type); > >> + > >> + if (locked) > >> + up_write(&fi->dio_rwsem); > >> + > >> stat_inc_data_blk_count(sbi, 1, gc_type); > >> } > >> } > >> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c > >> index edd1b35..dde57fb 100644 > >> --- a/fs/f2fs/super.c > >> +++ b/fs/f2fs/super.c > >> @@ -579,6 +579,7 @@ static struct inode *f2fs_alloc_inode(struct super_block *sb) > >> INIT_LIST_HEAD(&fi->gdirty_list); > >> INIT_LIST_HEAD(&fi->inmem_pages); > >> mutex_init(&fi->inmem_lock); > >> + init_rwsem(&fi->dio_rwsem); > >> > >> /* Will be used by directory only */ > >> fi->i_dir_level = F2FS_SB(sb)->dir_level; > >> -- > >> 2.7.2 ------------------------------------------------------------------------------ Attend Shape: An AT&T Tech Expo July 15-16. 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