linux-kernel - [PATCHv2 09/17] zram: check that backends array has at least one backend

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Date: Mon,  6 May 2024 16:58:22 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan@...nel.org>
Cc: linux-kernel@...r.kernel.org,
	linux-block@...r.kernel.org,
	Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: [PATCHv2 09/17] zram: check that backends array has at least one backend

Make sure that backends array has anything apart from the
sentinel NULL value.

We also select LZO_BACKEND if none backends were selected.

Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
---
 drivers/block/zram/Kconfig | 19 +++++++++++++------
 drivers/block/zram/zcomp.c |  8 ++++++++
 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/drivers/block/zram/Kconfig b/drivers/block/zram/Kconfig
index 1e0e7e5910b8..6aea609b795c 100644
--- a/drivers/block/zram/Kconfig
+++ b/drivers/block/zram/Kconfig
@@ -14,12 +14,6 @@ config ZRAM
 
 	  See Documentation/admin-guide/blockdev/zram.rst for more information.
 
-config ZRAM_BACKEND_LZO
-	bool "lzo and lzo-rle compression support"
-	depends on ZRAM
-	select LZO_COMPRESS
-	select LZO_DECOMPRESS
-
 config ZRAM_BACKEND_LZ4
 	bool "lz4 compression support"
 	depends on ZRAM
@@ -50,6 +44,19 @@ config ZRAM_BACKEND_842
 	select 842_COMPRESS
 	select 842_DECOMPRESS
 
+config ZRAM_BACKEND_FORCE_LZO
+	depends on ZRAM
+	def_bool !ZRAM_BACKEND_LZ4 && !ZRAM_BACKEND_LZ4HC && \
+		!ZRAM_BACKEND_ZSTD && !ZRAM_BACKEND_DEFLATE && \
+		!ZRAM_BACKEND_842
+
+config ZRAM_BACKEND_LZO
+	bool "lzo and lzo-rle compression support" if !ZRAM_BACKEND_FORCE_LZO
+	depends on ZRAM
+	default ZRAM_BACKEND_FORCE_LZO
+	select LZO_COMPRESS
+	select LZO_DECOMPRESS
+
 choice
 	prompt "Default zram compressor"
 	default ZRAM_DEF_COMP_LZORLE
diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
index 2a38126f4da3..d49791f724e9 100644
--- a/drivers/block/zram/zcomp.c
+++ b/drivers/block/zram/zcomp.c
@@ -209,6 +209,14 @@ struct zcomp *zcomp_create(const char *alg)
 	struct zcomp *comp;
 	int error;
 
+	/*
+	 * The backends array has a sentinel NULL value, so the minimum
+	 * size is 1. In order to be valid the array, apart from the
+	 * sentinel NULL element, should have at least one compression
+	 * backend selected.
+	 */
+	BUILD_BUG_ON(ARRAY_SIZE(backends) <= 1);
+
 	comp = kzalloc(sizeof(struct zcomp), GFP_KERNEL);
 	if (!comp)
 		return ERR_PTR(-ENOMEM);
-- 
2.45.0.rc1.225.g2a3ae87e7f-goog