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

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Message-ID: <e0d89f10-19b0-45db-948d-4c140c2dffa7@kernel.org>
Date: Thu, 20 Jun 2024 15:27:10 +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) [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?

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 */