From: Chao Yu <yuchao0@huawei.com>
To: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH 2/2] f2fs: avoid infinite GC loop due to stale atomic files
Date: Mon, 9 Sep 2019 16:05:22 +0800 [thread overview]
Message-ID: <bf0683d9-ac05-1edc-71ea-3d02f7b2fb55@huawei.com> (raw)
In-Reply-To: <20190909080108.GC21625@jaegeuk-macbookpro.roam.corp.google.com>
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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next prev parent reply other threads:[~2019-09-09 8:06 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-09 1:25 [f2fs-dev] [PATCH 1/2] f2fs: do not select same victim right again Jaegeuk Kim
2019-09-09 1:25 ` [f2fs-dev] [PATCH 2/2] f2fs: avoid infinite GC loop due to stale atomic files Jaegeuk Kim
2019-09-09 3:03 ` Chao Yu
2019-09-09 7:30 ` Jaegeuk Kim
2019-09-09 7:54 ` Chao Yu
2019-09-09 8:01 ` Jaegeuk Kim
2019-09-09 8:05 ` Chao Yu [this message]
2019-09-09 8:21 ` Jaegeuk Kim
2019-09-09 8:27 ` Chao Yu
2019-09-09 8:38 ` Jaegeuk Kim
2019-09-09 8:44 ` Jaegeuk Kim
2019-09-09 11:26 ` Chao Yu
2019-09-09 14:34 ` Jaegeuk Kim
2019-09-10 0:59 ` Chao Yu
2019-09-10 11:58 ` Jaegeuk Kim
2019-09-10 12:04 ` Chao Yu
2019-09-10 12:09 ` Jaegeuk Kim
2019-09-16 1:15 ` Chao Yu
2019-09-09 2:56 ` [f2fs-dev] [PATCH 1/2] f2fs: do not select same victim right again Chao Yu
2019-09-09 8:06 ` Jaegeuk Kim
2019-09-09 11:32 ` Chao Yu
2019-09-09 12:04 ` Jaegeuk Kim
2019-09-16 1:22 ` Chao Yu
2019-09-16 15:37 ` Jaegeuk Kim
2019-09-17 1:42 ` Chao Yu
2019-09-17 20:55 ` Jaegeuk Kim
2019-09-18 1:43 ` Chao Yu
2019-09-18 3:12 ` Jaegeuk Kim
2019-09-18 3:26 ` Chao Yu
2019-09-18 16:47 ` Jaegeuk Kim
2019-09-19 0:53 ` Chao Yu
2019-09-19 17:11 ` Jaegeuk Kim
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