linux-kernel - RE:(2) (2) (2) [f2fs-dev] [PATCH] Revert "f2fs: use flush command instead of FUA for zoned device"

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Date: Thu, 20 Jun 2024 16:56:34 +0900
From: Daejun Park <daejun7.park@...sung.com>
To: Chao Yu <chao@...nel.org>, "jaegeuk@...nel.org" <jaegeuk@...nel.org>,
	Wenjie Cheng <cwjhust@...il.com>
CC: "qwjhust@...il.com" <qwjhust@...il.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-f2fs-devel@...ts.sourceforge.net"
	<linux-f2fs-devel@...ts.sourceforge.net>, Daejun Park
	<daejun7.park@...sung.com>
Subject: RE:(2) (2) (2) [f2fs-dev] [PATCH] Revert
 "f2fs: use flush command instead of FUA for zoned device"

>On 2024/6/20 15:22, Daejun Park wrote:
>>> On 2024/6/20 13:56, Daejun Park wrote:
>>>> Hi Chao,
>>>>
>>>>> Jaegeuk,
>>>>>
>>>>> Quoted commit message from commit c550e25bca66 ("f2fs: use flush command
>>>>> instead of FUA for zoned device")
>>>>> "
>>>>> The block layer for zoned disk can reorder the FUA'ed IOs. Let's use flush
>>>>> command to keep the write order.
>>>>> "
>>>>>
>>>>> It seems mq-deadline use fifo queue and make queue depth of zone device
>>>>> as 1 to IO order, so why FUA'ed write node IOs can be reordered by block
>>>>> layer?
>>>>
>>>> While other writes are aligned by the mq-deadline, write with FUA is not passed
>>>> to the scheduler but handled at the block layer.
>>>
>>> Hi Daejun,
>>>
>>> IIUC, do you mean write w/ FUA may be handled directly in below path?
>>>
>>> - blk_mq_submit_bio
>>>    - op_is_flush && blk_insert_flush
>>
>> Hi Chao,
>>
>> Yes, I think the path caused an unaligned write when the zone lock was
>> being applied by mq-deadline.
>
>But, blk_insert_flush() may return false due to policy should be
>REQ_FSEQ_DATA or REQ_FSEQ_DATA REQ_FSEQ_POSTFLUSH, then
>blk_mq_insert_request() after blk_insert_flush() will be called?
>

I was just discussing the handling of FUAs in commit c550e25bca66,
which is not an issue in the current code as FUAs are handled correctly.

Thanks,


>Thanks,
>
>>
>>>
>>> Thanks,
>>>
>>>>
>>>> Thanks,
>>>> Daejun
>>>>
>>>>>
>>>>> Thanks,
>>>>>
>>>>> On 2024/6/14 8:48, Wenjie Cheng wrote:
>>>>>> This reverts commit c550e25bca660ed2554cbb48d32b82d0bb98e4b1.
>>>>>>
>>>>>> Commit c550e25bca660ed2554cbb48d32b82d0bb98e4b1 ("f2fs: use flush
>>>>>> command instead of FUA for zoned device") used additional flush
>>>>>> command to keep write order.
>>>>>>
>>>>>> Since Commit dd291d77cc90eb6a86e9860ba8e6e38eebd57d12 ("block:
>>>>>> Introduce zone write plugging") has enabled the block layer to
>>>>>> handle this order issue, there is no need to use flush command.
>>>>>>
>>>>>> Signed-off-by: Wenjie Cheng <cwjhust@...il.com>
>>>>>> ---
>>>>>>      fs/f2fs/file.c 3 +--
>>>>>>      fs/f2fs/node.c 2 +-
>>>>>>      2 files changed, 2 insertions(+), 3 deletions(-)
>>>>>>
>>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>>>>> index eae2e7908072..f08e6208e183 100644
>>>>>> --- a/fs/f2fs/file.c
>>>>>> +++ b/fs/f2fs/file.c
>>>>>> @@ -372,8 +372,7 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end,
>>>>>>               f2fs_remove_ino_entry(sbi, ino, APPEND_INO);
>>>>>>               clear_inode_flag(inode, FI_APPEND_WRITE);
>>>>>>      flush_out:
>>>>>> -        if ((!atomic && F2FS_OPTION(sbi).fsync_mode != FSYNC_MODE_NOBARRIER)
>>>>>> -            (atomic && !test_opt(sbi, NOBARRIER) && f2fs_sb_has_blkzoned(sbi)))
>>>>>> +        if (!atomic && F2FS_OPTION(sbi).fsync_mode != FSYNC_MODE_NOBARRIER)
>>>>>>                       ret = f2fs_issue_flush(sbi, inode->i_ino);
>>>>>>               if (!ret) {
>>>>>>                       f2fs_remove_ino_entry(sbi, ino, UPDATE_INO);
>>>>>> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
>>>>>> index 144f9f966690..c45d341dcf6e 100644
>>>>>> --- a/fs/f2fs/node.c
>>>>>> +++ b/fs/f2fs/node.c
>>>>>> @@ -1631,7 +1631,7 @@ static int __write_node_page(struct page *page, bool atomic, bool *submitted,
>>>>>>                       goto redirty_out;
>>>>>>               }
>>>>>> 
>>>>>> -        if (atomic && !test_opt(sbi, NOBARRIER) && !f2fs_sb_has_blkzoned(sbi))
>>>>>> +        if (atomic && !test_opt(sbi, NOBARRIER))
>>>>>>                       fio.op_flags = REQ_PREFLUSH REQ_FUA;
>>>>>> 
>>>>>>               /* should add to global list before clearing PAGECACHE status */