Message-ID: <sashiko-outbox-201621@kernel.org>
From: sashiko-bot@kernel.org
Subject: Re: [PATCH v2 10/15] lib/lz4: switch the compressor to the vendored
 sources
Reply-To: sashiko-reviews@lists.linux.dev
To: "Michal Wilczynski" <m.wilczynski@samsung.com>
Cc: linux-s390@vger.kernel.org, "Heiko Carstens" <hca@linux.ibm.com>, "Vasily
 Gorbik" <gor@linux.ibm.com>, "Alexander Gordeev" <agordeev@linux.ibm.com>, "Christian
 Borntraeger" <borntraeger@linux.ibm.com>
In-Reply-To: <20261106-lz4-vendor-upstream-v2-10-ee04c3f0d7dc@samsung.com>
References: <20261106-lz4-vendor-upstream-v2-0-ee04c3f0d7dc@samsung.com>
 <CGME20261106144305eucas1p17b3b27d403dc7d13b85cdd9a4bea83b9@eucas1p1.samsung.com>
 <20261106-lz4-vendor-upstream-v2-10-ee04c3f0d7dc@samsung.com>
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Date: Fri, 06 Nov 2026 14:52:04 +0000
Precedence: list

> Replace the forked compressor with thin entry points over the vendored
> lz4.c. LZ4_compress_default(), LZ4_compress_fast() and
> LZ4_compress_destSize() keep the trailing wrkmem argument and forward to
> upstream's *_extState() functions; the rest are plain forwarders.
>=20
> Upstream's LZ4_initStream() returns NULL for a misaligned workspace,
> which LZ4_compress_fast_extState() dereferences and
> LZ4_compress_destSize_extState() ignores. Check the alignment in the
> entry points, warn once and fail the call. In-tree callers allocate with
> kmalloc() or vmalloc() and are not affected.
>=20
> Compressed output differs from the fork's on a small fraction of inputs
> by a byte or two; both decode each other's output. Compressing 4K
> blocks, upstream is 2-4% faster on kernel source and binaries and up to
> 9% slower on datagen.
>=20
> LZ4_stream_t becomes an incomplete type, as upstream declares it, so
> <linux/lz4.h> and upstream's lz4.h can share a translation unit. The
> macros that laid out the forked structure go, and LZ4_MEM_COMPRESS keeps
> its value, 16416. zram, the only caller using sizeof(LZ4_stream_t), now
> allocates LZ4_MEM_COMPRESS bytes.
>=20
> Signed-off-by: Michal Wilczynski <m.wilczynski@samsung.com>

Sashiko has reviewed this patch and found no issues.

--=20
Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261106-lz4-vendor=
-upstream-v2-0-ee04c3f0d7dc@samsung.com?part=3D10