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From: Michal Wilczynski <m.wilczynski@samsung.com>
Date: Fri, 06 Nov 2026 15:42:43 +0100
Subject: [PATCH v2 03/15] zram: lz4hc: reset the dictionary stream once, not
 per page
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Message-Id: <20261106-lz4-vendor-upstream-v2-3-ee04c3f0d7dc@samsung.com>
In-Reply-To: <20261106-lz4-vendor-upstream-v2-0-ee04c3f0d7dc@samsung.com>
To: Michal Wilczynski <m.wilczynski@samsung.com>,  Nathan Chancellor
	<nathan@kernel.org>,  Nick Desaulniers <ndesaulniers@google.com>,  Bill
	Wendling <morbo@google.com>, Justin Stitt <justinstitt@google.com>,  Russell
	King <linux@armlinux.org.uk>,  Thomas Bogendoerfer
	<tsbogend@alpha.franken.de>,  "James E.J. Bottomley"
	<James.Bottomley@HansenPartnership.com>,  Helge Deller <deller@gmx.de>,
	Heiko Carstens <hca@linux.ibm.com>,  Vasily Gorbik <gor@linux.ibm.com>, 
	Alexander Gordeev <agordeev@linux.ibm.com>,  Christian Borntraeger
	<borntraeger@linux.ibm.com>,  Sven Schnelle <svens@linux.ibm.com>, Thomas
	Gleixner <tglx@kernel.org>,  Ingo Molnar <mingo@redhat.com>, Borislav Petkov
	<bp@alien8.de>,  Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org, 
	"H. Peter Anvin" <hpa@zytor.com>, Minchan Kim <minchan@kernel.org>,  Sergey
	Senozhatsky <senozhatsky@chromium.org>, Jens Axboe <axboe@kernel.dk>, 
	Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, llvm@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, 
	linux-parisc@vger.kernel.org, linux-s390@vger.kernel.org, 
	linux-block@vger.kernel.org, Yann Collet <yann.collet.73@gmail.com>,  Nick
	Terrell <terrelln@meta.com>, Gao Xiang <xiang@kernel.org>,  Chao Yu
	<chao@kernel.org>, Jaegeuk Kim <jaegeuk@kernel.org>,  Eric Biggers
	<ebiggers@kernel.org>,  Herbert Xu <herbert@gondor.apana.org.au>,  David
	Laight <david.laight.linux@gmail.com>,  Sungguk <sungguk.na@samsung.com>,
	Jaehoon Chung <jh80.chung@samsung.com>,  Marek Szyprowski
	<m.szyprowski@samsung.com>, linux-erofs@lists.ozlabs.org, 
	linux-f2fs-devel@lists.sourceforge.net, linux-crypto@vger.kernel.org
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References: <20261106-lz4-vendor-upstream-v2-0-ee04c3f0d7dc@samsung.com>
	<CGME20261106144252eucas1p272c9e37d66ad385db070f941879aecb1@eucas1p2.samsung.com>

With a dictionary, lz4hc_compress() calls LZ4_resetStreamHC() and then
LZ4_loadDictHC() for every page. LZ4_loadDictHC() re-initialises the
stream itself and keeps the level, so one reset at creation is enough.

The reset is cheap today, but upstream LZ4, which lib/lz4 moves to later
in this series, clears the whole 256K state in both calls. Reset once in
lz4hc_create() instead.

Signed-off-by: Michal Wilczynski <m.wilczynski@samsung.com>
---
 drivers/block/zram/backend_lz4hc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/zram/backend_lz4hc.c b/drivers/block/zram/backend_lz4hc.c
index d8aa01bb258fec760b597a88296dfaa4e0049693..06286c805cf7c56bd760f460cc854dc4014f293b 100644
--- a/drivers/block/zram/backend_lz4hc.c
+++ b/drivers/block/zram/backend_lz4hc.c
@@ -72,6 +72,7 @@ static int lz4hc_create(struct zcomp_params *params, struct zcomp_ctx *ctx)
 		zctx->cstrm = kzalloc_obj(*zctx->cstrm);
 		if (!zctx->cstrm)
 			goto error;
+		LZ4_resetStreamHC(zctx->cstrm, params->level);
 	}
 
 	return 0;
@@ -92,8 +93,7 @@ static int lz4hc_compress(struct zcomp_params *params, struct zcomp_ctx *ctx,
 				      req->dst_len, params->level,
 				      zctx->mem);
 	} else {
-		/* Cstrm needs to be reset */
-		LZ4_resetStreamHC(zctx->cstrm, params->level);
+		/* Reloading the dict resets cstrm and keeps its level */
 		ret = LZ4_loadDictHC(zctx->cstrm, params->dict,
 				     params->dict_sz);
 		if (ret != params->dict_sz)

-- 
2.34.1