Re: [PATCH] btrfs: add a test for btrfs fsverity

[Eric Biggers <ebiggers@kernel.org>]

Thanks for writing a test for this!

On Thu, Feb 04, 2021 at 03:24:26PM -0800, Boris Burkov wrote:
> There are some btrfs specific fsverity scenarios that don't map
> neatly onto the tests in generic/574, like holes, inline extents,
> and preallocated extents. Cover those in a btrfs specific test.
> 
> That test relies on assumptions about how the Merkle tree is stored
> by ext4/f2fs which don't apply to btrfs, so we also test Merkle tree
> corruption here. This could be merged by some generic abstraction.

The only part of generic/574 that cares where the Merkle tree is stored is
_fsv_scratch_corrupt_merkle_tree().  Couldn't that be updated to handle btrfs?

> Finally, that test relies extensively on fiemap, which is currently
> broken on btrfs for offsets and sizes that don't align to PAGE_SIZE,
> so put a simple regular file case in this test for now, while we fix
> fiemap or generalize extent lookup.

fiemap is only used by _fsv_scratch_corrupt_bytes().  It just wants to know the
list of extents that intersect the requested byte range.  Does that really not
work on btrfs if the range isn't page-aligned?

- Eric