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Rob Norris f62e6e1f98 compress: change zio_compress API to use ABDs 
This commit changes the frontend zio_compress_data and
zio_decompress_data APIs to take ABD points instead of buffer pointers.

All callers are updated to match. Any that already have an appropriate
ABD nearby now use it directly, while at the rest we create an one.

Internally, the ABDs are passed through to the provider directly.

Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Signed-off-by: Rob Norris <rob.norris@klarasystems.com>
 		2024-08-22 16:22:24 -07:00
..
include Cleanup of dead code suggested by Clang Static Analyzer (#14380) 2023-01-17 09:57:12 -08:00
lib Resolve WS-2021-0184 vulnerability in zstd 2023-02-02 15:12:51 -08:00
README.md linux: module: weld all but spl.ko into zfs.ko 2022-04-20 13:28:24 -07:00
zfs_zstd.c compress: change zio_compress API to use ABDs 2024-08-22 16:22:24 -07:00
zstd-in.c Import ZStandard v1.4.5 2020-08-20 10:30:06 -07:00
zstd_sparc.c Fix cross-endian interoperability of zstd 2021-08-30 14:13:46 -07:00

README.md

ZSTD-On-ZFS Library Manual

Introduction

This subtree contains the ZSTD library used in ZFS. It is heavily cut-down by dropping any unneeded files, and combined into a single file, but otherwise is intentionally unmodified. Please do not alter the file containing the zstd library, besides upgrading to a newer ZSTD release.

Tree structure:

  • zfs_zstd.c are the actual zfs kernel module hooks.
  • lib/ contains the unmodified version of the Zstandard library
  • zstd-in.c is our template file for generating the single-file library
  • include/: This directory contains supplemental includes for platform compatibility, which are not expected to be used by ZFS elsewhere in the future. Thus we keep them private to ZSTD.

Updating ZSTD

To update ZSTD the following steps need to be taken:

  1. Grab the latest release of ZSTD.
  2. Copy the files output by the following script to module/zstd/lib/: grep include [path to zstd]/contrib/single_file_libs/zstd-in.c | awk '{ print $2 }'
  3. Remove debug.c, threading.c, and zstdmt_compress.c.
  4. Update Makefiles with resulting file lists.
  5. Follow symbol renaming notes in include/zstd_compat_wrapper.h

Altering ZSTD and breaking changes

If ZSTD made changes that break compatibility or you need to make breaking changes to the way we handle ZSTD, it is required to maintain backwards compatibility.

We already save the ZSTD version number within the block header to be used to add future compatibility checks and/or fixes. However, currently it is not actually used in such a way.