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SubjectRe: [f2fs-dev] [PATCH] f2fs: fix deadlock between quota writes and checkpoint
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On 2020/8/4 11:54, Jaegeuk Kim wrote:
> On 08/04, Chao Yu wrote:
>> On 2020/7/29 15:02, Jaegeuk Kim wrote:
>>> f2fs_write_data_pages(quota_mapping)
>>> __f2fs_write_data_pages f2fs_write_checkpoint
>>> * blk_start_plug(&plug);
>>> * add bio in write_io[DATA]
>>> - block_operations
>>> - skip syncing quota by
>>> >DEFAULT_RETRY_QUOTA_FLUSH_COUNT
>>> - down_write(&sbi->node_write);
>>
>> f2fs_flush_merged_writes() will be called after block_operations(), why this doesn't
>> help?
>
> Well, I think bio can be added after f2fs_flush_merged_writes() as well.

- down_read(node_write)
- f2fs_do_write_data_page
- f2fs_trylock_op
- f2fs_outplace_write_data
- f2fs_submit_page_write

bio only be added under node_write lock? during f2fs_flush_merged_writes(), node_write
should have been held by checkpoint() avoiding quota data writeback & bio submission.

>
>>
>>> - f2fs_write_single_data_page
>>> - f2fs_do_write_data_page
>>> - f2fs_outplace_write_data
>>> - do_write_page
>>> - f2fs_allocate_data_block
>>> - down_write(node_write)
>>> - f2fs_wait_on_all_pages(F2FS_WB_CP_DATA);
>>>
>>> Signed-off-by: Daeho Jeong <daehojeong@google.com>
>>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
>>> ---
>>> fs/f2fs/checkpoint.c | 2 ++
>>> 1 file changed, 2 insertions(+)
>>>
>>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>>> index 8c782d3f324f0..99c8061da55b9 100644
>>> --- a/fs/f2fs/checkpoint.c
>>> +++ b/fs/f2fs/checkpoint.c
>>> @@ -1269,6 +1269,8 @@ void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)
>>> if (type == F2FS_DIRTY_META)
>>> f2fs_sync_meta_pages(sbi, META, LONG_MAX,
>>> FS_CP_META_IO);
>>> + else if (type == F2FS_WB_CP_DATA)
>>> + f2fs_submit_merged_write(sbi, DATA);
>>> io_schedule_timeout(DEFAULT_IO_TIMEOUT);
>>> }
>>> finish_wait(&sbi->cp_wait, &wait);
>>>
> .
>

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