Re: [PATCH 8/8] common: fix _require_xfs_io_command pwrite -A for various blocksizes

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

On Fri, Oct 24, 2025 at 02:48:00PM +0530, Nirjhar Roy (IBM) wrote:
> On Wed, 2025-10-15 at 09:38 -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <djwong@kernel.org>
> > 
> > In this predicate, we should test an atomic write of the minimum
> > supported size, not just 4k.  This fixes a problem where none of the
> > atomic write tests actually run on a 32k-fsblock xfs because you can't
> > do a sub-fsblock atomic write.
> > 
> > Cc: <fstests@vger.kernel.org> # v2025.04.13
> > Fixes: d90ee3b6496346 ("generic: add a test for atomic writes")
> > Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
> > ---
> >  common/rc |   14 +++++++++++---
> >  1 file changed, 11 insertions(+), 3 deletions(-)
> > 
> > 
> > diff --git a/common/rc b/common/rc
> > index 1b78cd0c358bb9..dcae5bc33b19ce 100644
> > --- a/common/rc
> > +++ b/common/rc
> > @@ -3030,16 +3030,24 @@ _require_xfs_io_command()
> >  	"pwrite")
> >  		# -N (RWF_NOWAIT) only works with direct vectored I/O writes
> >  		local pwrite_opts=" "
> > +		local write_size="4k"
> >  		if [ "$param" == "-N" ]; then
> >  			opts+=" -d"
> > -			pwrite_opts+="-V 1 -b 4k"
> > +			pwrite_opts+="-V 1 -b $write_size"
> Nit: We can still keep this to 4k (or any random size and not necessarily a size = fsblocksize),
> right?

Well, yes, the default will still be 4k on an old kernel that doesn't
support STATX_WRITE_ATOMIC.  For kernels that do support that flag,
write_size will now be whatever the filesystem claims is the minimum
write unit.

> >  		fi
> >  		if [ "$param" == "-A" ]; then
> >  			opts+=" -d"
> > -			pwrite_opts+="-V 1 -b 4k"
> > +			# try to write the minimum supported atomic write size
> > +			write_size="$($XFS_IO_PROG -f -c "statx -r -m $STATX_WRITE_ATOMIC" $testfile 2>/dev/null | \
> > +				grep atomic_write_unit_min | \
> > +				grep -o '[0-9]\+')"
> > +			if [ -z "$write_size" ] || [ "$write_size" = "0" ]; then
> > +				write_size="0 --not-supported"
> > +			fi
> > +			pwrite_opts+="-V 1 -b $write_size"
> >  		fi
> >  		testio=`$XFS_IO_PROG -f $opts -c \
> > -		        "pwrite $pwrite_opts $param 0 4k" $testfile 2>&1`
> > +		        "pwrite $pwrite_opts $param 0 $write_size" $testfile 2>&1`
> This looks good to me:
> 
> Reviewed-by: Nirjhar Roy (IBM) <nirjhar.roy.lists@gmail.com>

Thanks!

--D

> >  		param_checked="$pwrite_opts $param"
> >  		;;
> >  	"scrub"|"repair")
> > 
> 
>