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

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Date: Thu, 20 Jun 2024 15:12:42 +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) [f2fs-dev] [PATCH] Revert "f2fs: use flush command instead of
 FUA for zoned device"

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

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 */