From d93435c3fba4a47b773693b0c8992470d38510d5 Mon Sep 17 00:00:00 2001 From: Sergey Senozhatsky Date: Thu, 25 Jun 2015 15:00:32 -0700 Subject: [PATCH] zram: check comp algorithm availability earlier Improvement idea by Marcin Jabrzyk. comp_algorithm_store() silently accepts any supplied algorithm name, because zram performs algorithm availability check later, during the device configuration phase in disksize_store() and emits the following error: "zram: Cannot initialise %s compressing backend" this error line is somewhat generic and, besides, can indicate a failed attempt to allocate compression backend's working buffers. add algorithm availability check to comp_algorithm_store(): echo lzz > /sys/block/zram0/comp_algorithm -bash: echo: write error: Invalid argument Signed-off-by: Sergey Senozhatsky Reported-by: Marcin Jabrzyk Acked-by: Minchan Kim Cc: Nitin Gupta Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/block/zram/zcomp.c | 5 +++++ drivers/block/zram/zcomp.h | 1 + drivers/block/zram/zram_drv.c | 3 +++ 3 files changed, 9 insertions(+) diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c index a1a8b8ee9fda..965d1afb0eaa 100644 --- a/drivers/block/zram/zcomp.c +++ b/drivers/block/zram/zcomp.c @@ -286,6 +286,11 @@ ssize_t zcomp_available_show(const char *comp, char *buf) return sz; } +bool zcomp_available_algorithm(const char *comp) +{ + return find_backend(comp) != NULL; +} + bool zcomp_set_max_streams(struct zcomp *comp, int num_strm) { return comp->set_max_streams(comp, num_strm); diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h index c59d1fca72c0..46e2b9f8f1f0 100644 --- a/drivers/block/zram/zcomp.h +++ b/drivers/block/zram/zcomp.h @@ -51,6 +51,7 @@ struct zcomp { }; ssize_t zcomp_available_show(const char *comp, char *buf); +bool zcomp_available_algorithm(const char *comp); struct zcomp *zcomp_create(const char *comp, int max_strm); void zcomp_destroy(struct zcomp *comp); diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index d94696b28a85..fb655e8d1e3b 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -378,6 +378,9 @@ static ssize_t comp_algorithm_store(struct device *dev, if (sz > 0 && zram->compressor[sz - 1] == '\n') zram->compressor[sz - 1] = 0x00; + if (!zcomp_available_algorithm(zram->compressor)) + len = -EINVAL; + up_write(&zram->init_lock); return len; } -- 2.20.1