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
