Re: [PATCH 3/3] xfs/559: adapt to kernels that use large folios for writes

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On Fri, Sep 01, 2023 at 09:56:29PM -0700, Darrick J. Wong wrote:
> On Sat, Sep 02, 2023 at 03:08:02AM +0800, Zorro Lang wrote:
> > On Tue, Aug 29, 2023 at 04:03:49PM -0700, Darrick J. Wong wrote:
> > > From: Darrick J. Wong <djwong@xxxxxxxxxx>
> > > 
> > > The write invalidation code in iomap can only be triggered for writes
> > > that span multiple folios.  If the kernel reports a huge page size,
> > > scale up the write size.
> > > 
> > > Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
> > > ---
> > >  tests/xfs/559 |   29 ++++++++++++++++++++++++++++-
> > >  1 file changed, 28 insertions(+), 1 deletion(-)
> > > 
> > > 
> > > diff --git a/tests/xfs/559 b/tests/xfs/559
> > > index cffe5045a5..64fc16ebfd 100755
> > > --- a/tests/xfs/559
> > > +++ b/tests/xfs/559
> > > @@ -42,11 +42,38 @@ $XFS_IO_PROG -c 'chattr -x' $SCRATCH_MNT &> $seqres.full
> > >  _require_pagecache_access $SCRATCH_MNT
> > >  
> > >  blocks=10
> > > -blksz=$(_get_page_size)
> > > +
> > > +# If this kernel advertises huge page support, it's possible that it could be
> > > +# using large folios for the page cache writes.  It is necessary to write
> > > +# multiple folios (large or regular) to triggering the write invalidation,
> > > +# so we'll scale the test write size accordingly.
> > > +blksz=$(_get_hugepagesize)
> > 
> > Isn't _require_hugepages needed if _get_hugepagesize is used?
> 
> Nope -- if the kernel doesn't support hugepages, then _get_hugepagesize
> returns the empty string...
> 
> > Thanks,
> > Zorro
> > 
> > > +base_pagesize=$(_get_page_size)
> > > +test -z "$blksz" && blksz=${base_pagesize}
> 
> ...and this line will substitute in the base page size as the block size.

Oh yes, you catch it at here :) OK, so the whole patchset is good to me,

Reviewed-by: Zorro Lang <zlang@xxxxxxxxxx>

> 
> --D
> 
> > >  filesz=$((blocks * blksz))
> > >  dirty_offset=$(( filesz - 1 ))
> > >  write_len=$(( ( (blocks - 1) * blksz) + 1 ))
> > >  
> > > +# The write invalidation that we're testing below can only occur as part of
> > > +# a single large write.  The kernel limits writes to one base page less than
> > > +# 2GiB to prevent lengthy IOs and integer overflows.  If the block size is so
> > > +# huge (e.g. 512M huge pages on arm64) that we'd exceed that, reduce the number
> > > +# of blocks to get us under the limit.
> > > +max_writesize=$((2147483647 - base_pagesize))
> > > +if ((write_len > max_writesize)); then
> > > +	blocks=$(( ( (max_writesize - 1) / blksz) + 1))
> > > +	# We need at least three blocks in the file to test invalidation
> > > +	# between writes to multiple folios.  If we drop below that,
> > > +	# reconfigure ourselves with base pages and hope for the best.
> > > +	if ((blocks < 3)); then
> > > +		blksz=$base_pagesize
> > > +		blocks=10
> > > +	fi
> > > +	filesz=$((blocks * blksz))
> > > +	dirty_offset=$(( filesz - 1 ))
> > > +	write_len=$(( ( (blocks - 1) * blksz) + 1 ))
> > > +fi
> > > +
> > >  # Create a large file with a large unwritten range.
> > >  $XFS_IO_PROG -f -c "falloc 0 $filesz" $SCRATCH_MNT/file >> $seqres.full
> > >  
> > > 
> > 
> 




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