Re: [PATCH] Btrfs: fix extent buffer bitmap tests on big-endian systems
On Wed, Jul 13, 2016 at 2:21 AM, Omar Sandoval <osandov@osandov.com> wrote:
> From: Omar Sandoval <osandov@fb.com>
>
> The in-memory bitmap code manipulates words and is therefore sensitive
> to endianness, while the extent buffer bitmap code addresses bytes and
> is byte-order agnostic. Because the byte addressing of the extent buffer
> bitmaps is equivalent to a little-endian in-memory bitmap, the extent
> buffer bitmap tests fail on big-endian systems.
>
> 34b3e6c92af1 ("Btrfs: self-tests: Fix extent buffer bitmap test fail on
> BE system") worked around another endianness bug in the tests but missed
> this one because ed9e4afdb055 ("Btrfs: self-tests: Execute page
> straddling test only when nodesize < PAGE_SIZE") disables this part of
> the test on ppc64. That change lost the original meaning of the test,
> however. We really want to test that an equivalent series of operations
> using the in-memory bitmap API and the extent buffer bitmap API produces
> equivalent results.
>
> To fix this, don't use memcmp_extent_buffer() or write_extent_buffer();
> do everything bit-by-bit.
Just tested patched kernel, able to load btrfs module and mount fs.
Thanks a lot!
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