Messages in this thread | | | Subject | Re: [f2fs-dev] [PATCH 2/2] f2fs: avoid infinite GC loop due to stale atomic files | From | Chao Yu <> | Date | Mon, 9 Sep 2019 16:05:22 +0800 |
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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().
> >> >> Thanks, >> >>> >>>> >>>> So my question is why below logic didn't handle such condition well? >>>> >>>> f2fs_gc() >>>> >>>> if (has_not_enough_free_secs(sbi, sec_freed, 0)) { >>>> if (skipped_round <= MAX_SKIP_GC_COUNT || >>>> skipped_round * 2 < round) { >>>> segno = NULL_SEGNO; >>>> goto gc_more; >>>> } >>>> >>>> if (first_skipped < last_skipped && >>>> (last_skipped - first_skipped) > >>>> sbi->skipped_gc_rwsem) { >>>> f2fs_drop_inmem_pages_all(sbi, true); >>> >>> This is doing nothing, since f2fs_commit_inmem_pages() removed the inode >>> from inmem list. >>> >>>> segno = NULL_SEGNO; >>>> goto gc_more; >>>> } >>>> if (gc_type == FG_GC && !is_sbi_flag_set(sbi, SBI_CP_DISABLED)) >>>> ret = f2fs_write_checkpoint(sbi, &cpc); >>>> } >>>> >>>>> } else { >>>>> ret = f2fs_do_sync_file(filp, 0, LLONG_MAX, 1, false); >>>>> } >>>>> >>> . >>> > . >
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