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.

Link: https://lkml.kernel.org/r/20240902105656.1383858-13-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nick Terrell <terrelln@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/drivers/block/zram/Kconfig b/drivers/block/zram/Kconfig
index 1e0e7e5910b83341fc3efbedd3f4ef94f17e4de8..6aea609b795c2f36be8a92c98cc510d7ca0c49eb 100644 (file)
--- 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 94e1c95032678fc3a6bbc8c7a440358f36a1a425..76d21ee7706759b7cfa71f6a6e98a0986fdbbdef 100644 (file)
--- a/drivers/block/zram/zcomp.c
+++ b/drivers/block/zram/zcomp.c
@@ -192,6 +192,14 @@ 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);