Messages in this thread Patch in this message | | | Date | Mon, 9 Sep 2019 09:44:58 +0100 | From | Jaegeuk Kim <> | Subject | Re: [f2fs-dev] [PATCH 2/2] f2fs: avoid infinite GC loop due to stale atomic files |
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On 09/09, Jaegeuk Kim wrote: > On 09/09, Chao Yu wrote: > > On 2019/9/9 16:21, Jaegeuk Kim wrote: > > > On 09/09, Chao Yu wrote: > > >> On 2019/9/9 16:01, Jaegeuk Kim wrote: > > >>> On 09/09, Chao Yu wrote: > > >>>> On 2019/9/9 15:30, Jaegeuk Kim wrote: > > >>>>> On 09/09, Chao Yu wrote: > > >>>>>> On 2019/9/9 9:25, Jaegeuk Kim wrote: > > >>>>>>> If committing atomic pages is failed when doing f2fs_do_sync_file(), we can > > >>>>>>> get commited pages but atomic_file being still set like: > > >>>>>>> > > >>>>>>> - inmem: 0, atomic IO: 4 (Max. 10), volatile IO: 0 (Max. 0) > > >>>>>>> > > >>>>>>> If GC selects this block, we can get an infinite loop like this: > > >>>>>>> > > >>>>>>> f2fs_submit_page_bio: dev = (253,7), ino = 2, page_index = 0x2359a8, oldaddr = 0x2359a8, newaddr = 0x2359a8, rw = READ(), type = COLD_DATA > > >>>>>>> f2fs_submit_read_bio: dev = (253,7)/(253,7), rw = READ(), DATA, sector = 18533696, size = 4096 > > >>>>>>> f2fs_get_victim: dev = (253,7), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 4355, cost = 1, ofs_unit = 1, pre_victim_secno = 4355, prefree = 0, free = 234 > > >>>>>>> f2fs_iget: dev = (253,7), ino = 6247, pino = 5845, i_mode = 0x81b0, i_size = 319488, i_nlink = 1, i_blocks = 624, i_advise = 0x2c > > >>>>>>> f2fs_submit_page_bio: dev = (253,7), ino = 2, page_index = 0x2359a8, oldaddr = 0x2359a8, newaddr = 0x2359a8, rw = READ(), type = COLD_DATA > > >>>>>>> f2fs_submit_read_bio: dev = (253,7)/(253,7), rw = READ(), DATA, sector = 18533696, size = 4096 > > >>>>>>> f2fs_get_victim: dev = (253,7), type = No TYPE, policy = (Foreground GC, LFS-mode, Greedy), victim = 4355, cost = 1, ofs_unit = 1, pre_victim_secno = 4355, prefree = 0, free = 234 > > >>>>>>> f2fs_iget: dev = (253,7), ino = 6247, pino = 5845, i_mode = 0x81b0, i_size = 319488, i_nlink = 1, i_blocks = 624, i_advise = 0x2c > > >>>>>>> > > >>>>>>> In that moment, we can observe: > > >>>>>>> > > >>>>>>> [Before] > > >>>>>>> Try to move 5084219 blocks (BG: 384508) > > >>>>>>> - data blocks : 4962373 (274483) > > >>>>>>> - node blocks : 121846 (110025) > > >>>>>>> Skipped : atomic write 4534686 (10) > > >>>>>>> > > >>>>>>> [After] > > >>>>>>> Try to move 5088973 blocks (BG: 384508) > > >>>>>>> - data blocks : 4967127 (274483) > > >>>>>>> - node blocks : 121846 (110025) > > >>>>>>> Skipped : atomic write 4539440 (10) > > >>>>>>> > > >>>>>>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> > > >>>>>>> --- > > >>>>>>> fs/f2fs/file.c | 10 +++++----- > > >>>>>>> 1 file changed, 5 insertions(+), 5 deletions(-) > > >>>>>>> > > >>>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > > >>>>>>> index 7ae2f3bd8c2f..68b6da734e5f 100644 > > >>>>>>> --- a/fs/f2fs/file.c > > >>>>>>> +++ b/fs/f2fs/file.c > > >>>>>>> @@ -1997,11 +1997,11 @@ static int f2fs_ioc_commit_atomic_write(struct file *filp) > > >>>>>>> goto err_out; > > >>>>>>> > > >>>>>>> ret = f2fs_do_sync_file(filp, 0, LLONG_MAX, 0, true); > > >>>>>>> - if (!ret) { > > >>>>>>> - clear_inode_flag(inode, FI_ATOMIC_FILE); > > >>>>>>> - F2FS_I(inode)->i_gc_failures[GC_FAILURE_ATOMIC] = 0; > > >>>>>>> - stat_dec_atomic_write(inode); > > >>>>>>> - } > > >>>>>>> + > > >>>>>>> + /* doesn't need to check error */ > > >>>>>>> + clear_inode_flag(inode, FI_ATOMIC_FILE); > > >>>>>>> + F2FS_I(inode)->i_gc_failures[GC_FAILURE_ATOMIC] = 0; > > >>>>>>> + stat_dec_atomic_write(inode); > > >>>>>> > > >>>>>> If there are still valid atomic write pages linked in .inmem_pages, it may cause > > >>>>>> memory leak when we just clear FI_ATOMIC_FILE flag. > > >>>>> > > >>>>> f2fs_commit_inmem_pages() should have flushed them. > > >>>> > > >>>> Oh, we failed to flush its nodes. > > >>>> > > >>>> However we won't clear such info if we failed to flush inmen pages, it looks > > >>>> inconsistent. > > >>>> > > >>>> Any interface needed to drop inmem pages or clear ATOMIC_FILE flag in that two > > >>>> error path? I'm not very clear how sqlite handle such error. > > >>> > > >>> f2fs_drop_inmem_pages() did that, but not in this case. > > >> > > >> What I mean is, for any error returned from atomic_commit() interface, should > > >> userspace application handle it with consistent way, like trigger > > >> f2fs_drop_inmem_pages(), so we don't need to handle it inside atomic_commit(). > > > > > > f2fs_ioc_abort_volatile_write() will be triggered. > > > > If userspace can do this, we can get rid of this patch, or am I missing sth? > > We don't know when that will come. And, other threads are waiting for GC here. >
Actually, we can call this.
--- fs/f2fs/file.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 7ae2f3bd8c2f..98e2f58467d3 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -1997,11 +1997,7 @@ static int f2fs_ioc_commit_atomic_write(struct file *filp) goto err_out; ret = f2fs_do_sync_file(filp, 0, LLONG_MAX, 0, true); - if (!ret) { - clear_inode_flag(inode, FI_ATOMIC_FILE); - F2FS_I(inode)->i_gc_failures[GC_FAILURE_ATOMIC] = 0; - stat_dec_atomic_write(inode); - } + f2fs_drop_inmem_pages(inode); } else { ret = f2fs_do_sync_file(filp, 0, LLONG_MAX, 1, false); } -- 2.19.0.605.g01d371f741-goog
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