Re: [PATCH 1/6] generic/765: fix a few issues

["Darrick J. Wong" <djwong@kernel.org>]

On Thu, May 15, 2025 at 09:16:12AM +0100, John Garry wrote:
> On 14/05/2025 16:38, Darrick J. Wong wrote:
> > > > --- a/common/rc
> > > > +++ b/common/rc
> > > > @@ -2989,7 +2989,7 @@ _require_xfs_io_command()
> > > >    		fi
> > > >    		if [ "$param" == "-A" ]; then
> > > >    			opts+=" -d"
> > > > -			pwrite_opts+="-D -V 1 -b 4k"
> > > > +			pwrite_opts+="-d -V 1 -b 4k"
> > > according to the documentation for -b, 4096 is the default (so I don't think
> > > that we need to set it explicitly). But is that flag even relevant to
> > > pwritev2?
> > The documentation is wrong -- on XFS the default is the fs blocksize.
> > Everywhere else is 4k.
> 
> Right, I see that in init_cvtnum()
> 
> However, from checking write_buffer(), we seem to split writes on this
> blocksize - that does not seem proper in this instance.
> 
> Should we really be doing something like:
> 
> xfs_io -d -C "pwrite -b $SIZE -V 1 -A -D 0 $SIZE" file

In _require_xfs_io_command?  That only writes the first 4k of a file, so
matching buffer size is ok.

Are you asking if _require_xfs_io_command should seek out the filesystem
block size, and use that for the buffer and write size arguments instead
of hardcoding 4k?  For atomic writes, maybe it should be doing this,
since the fs blocksize could be 64k.

--D

> Thanks,
> John
>