[PATCH 0/3] btrfs: fix and simplify the inline extent decompression path for subpage

[Qu Wenruo <wqu@suse.com>]

There is a long existing bug in subpage inline extent reflinking to
another location.

The bug is caused by an existing bad code, which is from the beginning
of btrfs.
The bad code is never properly explained and got further copied into new
compression code.

The bad condition never got properly triggered by different reasons for
different platforms:

- On 4K page sized system, the @start_byte is always 0
  Thus the existing checks are all dead code, thus never triggered.

- For subpage (4K sectorsize 64K page size) cases, inline extent
  creation is disable for a different reason
  Since no inline extent can be created, there is no way to reflink
  any inlined extent thus no way to trigger it.

The fixes are mostly going to rework the decompression loop, making sure
the input and output buffer are always large enough for inline extent.
Thus no need for any loop, but a single decompression call.

But the difficulty lies in how to properly test the bug.
For now I'm only doing cross-platform tests, using image created on
x86_64, and do the reflink on aarch64.
Not sure if it's possible to upload a binary image for fstests, or I
don't have any good way to test the bug.

Qu Wenruo (3):
  btrfs: zlib: fix and simplify the inline extent decompression
  btrfs: lzo: fix and simplify the inline extent decompression
  btrfs: zstd: fix and simplify the inline extent decompression

 fs/btrfs/compression.c | 23 +++++++++----
 fs/btrfs/compression.h |  6 ++--
 fs/btrfs/lzo.c         | 34 +++++--------------
 fs/btrfs/super.h       |  3 ++
 fs/btrfs/zlib.c        | 73 +++++++++++------------------------------
 fs/btrfs/zstd.c        | 74 +++++++++++++-----------------------------
 6 files changed, 72 insertions(+), 141 deletions(-)

-- 
2.43.0