Re: [PATCH] xfs/242: fix for archs with 8k page size

[Dwight Engen <dwight.engen@oracle.com>]

Hi Dave, any further comments on this?

On Thu, 16 Oct 2014 11:29:49 -0400
Dwight Engen <dwight.engen@oracle.com> wrote:

> On Wed, 8 Oct 2014 15:33:41 +1100
> Dave Chinner <david@fromorbit.com> wrote:
> 
> > On Tue, Oct 07, 2014 at 07:12:59PM -0400, Dwight Engen wrote:
> > > This test was failing on sparc64 because there is a minimum
> > > granularity of PAGE_CACHE_SIZE in
> > > xfs_vnodeops.c:xfs_zero_file_space(). This change follows the
> > > approach taken in xfs/194 to filter the bmap output to be in terms
> > > of "blocksize" which is computed from pagesize.
> > 
> > xfs/194 existed long before xfs/242, so it's not necessarily the
> > best example to follow. You've missed various things that make the
> > special hackery xfs/194 does to make it work. e.g.  clearing
> > mkfs/mount options. Your change doesn't do this, so it will make it
> > fail on CRC enable XFS filesystems because 4k / 8 = 512 bytes and
> > that's smaller than the minimum block size support on CRC enabled
> > XFS filesystems.
> 
> Hi Dave, I sure did miss that 194 was doing unset MKFS_OPTIONS. Partly
> because running check '*/194' outputs:
> 
> MKFS_OPTIONS  -- -f -bsize=4096 /dev/vdiskd
> 
> but this is only for the mkfs that check itself does, and as you note
> 194 will redo the mkfs with its computed block size. Thats a bit
> confusing :( 242 doesn't do a second mkfs, so there isn't really a
> need to unset MKFS_OPTIONS.
> 
> What I thought 194 was doing, and what I made 242 do was to be page
> size independent by computing the size of things and filtering the
> output to be in units of some factor of a page size, which is why I
> put blksize in quotes, its not the actual block size (ie we don't
> pass it to mkfs). Maybe I should have used a different name for less
> confusion, suggestions welcome. Doing this does make it so 242 passes
> with no MKFS_OPTIONS (which will be 4k blocksize) or with
> MKFS_OPTIONS="-b size=8k", and both of those with -m crc=1 also. 
> 
> > > _test_generic_punch is modified to optionally take multiple as an
> > > argument, so the file under test will be twice the size on an 8k
> > > machine as a 4k machine. Since the files will be different sizes,
> > > we can no longer use md5sum so od -x is used instead with the byte
> > > offsets converted to "blocksize" offsets.
> > 
> > Brian posted patches yesterday on the XFS list to fix zero range
> > problems, and they remove the page size rounding from
> > xfs_zero_file_space(). Hence this strange corner case behaviour is
> > likely to go away real soon, and so I don't think we should change
> > the test to work around it now...
> 
> That sounds good, but I'd think we want 242 to be able to pass
> regardless of page size on 3.12-3.17 too?
> 
> > Would would be much more useful for you to do would with a platform
> > like sparc64 is use it to test MKFS_OPTION="-b size=8k" and make all
> > these extent-map-output dependent tests work properly with >4k block
> > size filesystems.  ;)
> 
> This does do that for 242 :) I can look at the others also if the
> approach here is okay. Thanks.
> 
> > Cheers,
> > 
> > Dave.
> 
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