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 16:01:05 +0800
From: Chao Yu <chao@...nel.org>
To: daejun7.park@...sung.com, "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>
Subject: Re: (2) (2) (2) [f2fs-dev] [PATCH] Revert "f2fs: use flush command
 instead of FUA for zoned device"

On 2024/6/20 15:56, Daejun Park wrote:
>> 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.

Yup, I think it needs to be reverted. :)

Thanks,

> 
> 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 */