smb: client: compress: LZ77 code improvements cleanup

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- Check data compressibility with some heuristics (copied from
  btrfs):
  - should_compress() final decision is is_compressible(data)

- Cleanup compress/lz77.h leaving only lz77_compress() exposed:
  - Move parts to compress/lz77.c, while removing the rest of it
    because they were either unused, used only once, were
    implemented wrong (thanks to David Howells for the help)

- Updated the compression parameters (still compatible with
  Windows implementation) trading off ~20% compression ratio
  for ~40% performance:
  - min match len: 3 -> 4
  - max distance: 8KiB -> 1KiB
  - hash table type: u32 * -> u64 *

Known bugs:
This implementation currently works fine in general, but breaks with
some payloads used during testing.  Investigation ongoing, to be
fixed in a next commit.

Signed-off-by: Enzo Matsumiya <ematsumiya@suse.de>
Co-developed-by: David Howells <dhowells@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

...

This commit is contained in:

Enzo Matsumiya 2024-09-06 14:41:50 -03:00 • committed by Steve French

parent f046d71e84

commit 94ae8c3fee

4 changed files with 532 additions and 463 deletions

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367

fs/smb/client/compress.c

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85

fs/smb/client/compress.h

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268

fs/smb/client/compress/lz77.c

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275

fs/smb/client/compress/lz77.h

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