Hi
Kindly ping. ^_^
Best Regards,
Xiao Yang
-----Original Message-----
From: Yang, Xiao/杨 晓 <yangx.jy@xxxxxxxxxxx>
Sent: 2022年11月17日 10:28
To: Stefan Roesch <shr@xxxxxxxx>; shr@xxxxxx; djwong@xxxxxxxxxx
Cc: linux-xfs@xxxxxxxxxxxxxxx; Ruan, Shiyang/阮 世阳 <ruansy.fnst@xxxxxxxxxxx>
Subject: Re: [PATCH] xfs: Call kiocb_modified() for buffered write
On 2022/11/17 3:00, Stefan Roesch write:
>
> On 11/16/22 6:42 AM, Xiao Yang wrote:
>> kiocb_modified() should be used for sync/async buffered write because
>> it will return -EAGAIN when IOCB_NOWAIT is set. Unfortunately,
>> kiocb_modified() is used by the common xfs_file_write_checks() which
>> is called by all types of write(i.e. buffered/direct/dax write).
>> This issue makes generic/471 with xfs always get the following error:
>> --------------------------------------------------------
>> QA output created by 471
>> pwrite: Resource temporarily unavailable wrote 8388608/8388608 bytes
>> at offset 0 XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX
>> ops/sec)
>> pwrite: Resource temporarily unavailable ...
>> --------------------------------------------------------
>>
> There have been earlier discussions about this. Snippet from the
> earlier discussion:
>
> "generic/471 complains because it expects any write done with
> RWF_NOWAIT to succeed as long as the blocks for the write are already instantiated.
> This isn't necessarily a correct assumption, as there are other
> conditions that can cause an RWF_NOWAIT write to fail with -EAGAIN
> even if the range is already there."
Hi Stefan,
Thanks for your reply.
Could you give me the URL about the earlier discussions?
kiocb_modified() makes all types of write always get -EAGAIN when RWF_NOWAIT is set. I don't think this patch[1] is correct because it changed the original logic. The original logic only makes buffered write get -EOPNOTSUPP when RWF_NOWAIT is set.
---------------------------------------------
static int file_modified_flags(struct file *file, int flags) { ...
if (flags & IOCB_NOWAIT)
return -EAGAIN;
...
}
int kiocb_modified(struct kiocb *iocb)
{
return file_modified_flags(iocb->ki_filp, iocb->ki_flags); }
---------------------------------------------
PS: kiocb_modified() is used by the common xfs_file_write_checks() which is called by all types of write(i.e. buffered/direct/dax write).
>
> So the test itself probably needs fixing.
In my opinion, both kernel and the test probably need to be fixed.
[1] 1aa91d9c9933 ("xfs: Add async buffered write support")
Best Regards,
Xiao Yang
