Messages in this thread | | | Subject | Re: [PATCH v3] f2fs: fix to avoid data update racing between GC and DIO | From | Chao Yu <> | Date | Tue, 12 Jul 2016 09:28:26 +0800 |
| |
On 2016/7/10 0:22, Jaegeuk Kim wrote: > 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: [<ffffffff81299c3b>] do_blockdev_direct_IO+0x1db/0x2310 >>> [ 502.480948] >>> [ 502.480948] but task is already holding lock: >>> [ 502.480959] (&fi->dio_rwsem){.+.+.+}, at: [<ffffffffc081e2b1>] 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] [<ffffffff810e51c3>] lock_acquire+0xd3/0x220 >>> [ 502.481071] [<ffffffff818d1921>] down_read+0x51/0xa0 >>> [ 502.481089] [<ffffffffc081e2b1>] f2fs_direct_IO+0xd1/0x3d0 [f2fs] >>> [ 502.481114] [<ffffffff811c34c7>] generic_file_direct_write+0xa7/0x160 >>> [ 502.481133] [<ffffffff811c363d>] __generic_file_write_iter+0xbd/0x1e0 >>> [ 502.481149] [<ffffffffc080437b>] f2fs_file_write_iter+0xdb/0x100 [f2fs] >>> [ 502.481173] [<ffffffff81253a88>] __vfs_write+0xc8/0x140 >>> [ 502.481190] [<ffffffff81254c55>] vfs_write+0xb5/0x1b0 >>> [ 502.481205] [<ffffffff81255fe9>] SyS_write+0x49/0xa0 >>> [ 502.481220] [<ffffffff818d4100>] entry_SYSCALL_64_fastpath+0x23/0xc1 >>> [ 502.481236] >>> [ 502.481236] -> #0 (&sb->s_type->i_mutex_key#18){+.+.+.}: >>> [ 502.481264] [<ffffffff810e481c>] __lock_acquire+0x161c/0x1940 >>> [ 502.481280] [<ffffffff810e51c3>] lock_acquire+0xd3/0x220 >>> [ 502.481296] [<ffffffff818d1b9a>] down_write+0x5a/0xc0 >>> [ 502.481312] [<ffffffff81299c3b>] do_blockdev_direct_IO+0x1db/0x2310 >>> [ 502.481328] [<ffffffff8129bdaa>] __blockdev_direct_IO+0x3a/0x40 >>> [ 502.481344] [<ffffffffc081e2e4>] f2fs_direct_IO+0x104/0x3d0 [f2fs] >>> [ 502.481368] [<ffffffff811c40a9>] generic_file_read_iter+0x689/0x7e0 >>> [ 502.481384] [<ffffffff812545d1>] __vfs_read+0xc1/0x130 >>> [ 502.481399] [<ffffffff81254af1>] vfs_read+0x91/0x140 >>> [ 502.481414] [<ffffffff81255f49>] SyS_read+0x49/0xa0 >>> [ 502.481429] [<ffffffff818d4100>] 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?
If we reuse inode->i_rwsem here, we will suffer the same issue when we remove i_rwsem lock in dio writer or dio reader for better concurrency.
So I think it's better to use separate lock to just fix this issue.
Thanks,
> >> >> Thanks, >> >>> [ 502.483285] >>> [ 502.483285] *** DEADLOCK *** >>> [ 502.483285] >>> [ 502.484018] 1 lock held by fsstress/10729: >>> [ 502.484262] #0: (&fi->dio_rwsem){.+.+.+}, at: [<ffffffffc081e2b1>] f2fs_direct_IO+0xd1/0x3d0 [f2fs] >>> >>> Thanks, >>> >>> On Thu, Jul 07, 2016 at 12:49:12PM +0800, Chao Yu wrote: >>>> From: Chao Yu <yuchao0@huawei.com> >>>> >>>> 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 <yuchao0@huawei.com> >>>> --- >>>> 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 > > . >
| |