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[PATCH] zram: fix max pool limitation

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  [PATCH] zram: fix max pool limitation Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2015-08-11 15:40 +0200
    Re: [PATCH] zram: fix max pool limitation Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2015-08-11 16:50 +0200

#1205144 — [PATCH] zram: fix max pool limitation

zram_meta_alloc() constructs a pool name for zs_create_pool() call
as
 snprintf(pool_name, sizeof(pool_name), "zram%d", device_id);

However, it defines pool name buffer to be only 8 chars long
(minus trailing zero), which means that we can have only 1000
pool names: zram0 -- zram999.

With CONFIG_ZSMALLOC_STAT enabled an attempt to create a device
zram1000 can fail if device zram100 already exists, because
snprintf() will truncate new pool name to zram100 and pass it
to debugfs_create_dir(), causing:

  debugfs dir <zram100> creation failed
  zram: Error creating memory pool

... and so on (zram101 - zram1010, etc).

Fix it by increasing pool_name buffer size to 11:
-- zram prefix (length 4)
-- int device_id can use up to 10 chars
-- terminating zero byte

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
 drivers/block/zram/zram_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index b088ca9..1dec01d 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -502,7 +502,7 @@ static void zram_meta_free(struct zram_meta *meta, u64 disksize)
 static struct zram_meta *zram_meta_alloc(int device_id, u64 disksize)
 {
 	size_t num_pages;
-	char pool_name[8];
+	char pool_name[15];
 	struct zram_meta *meta = kmalloc(sizeof(*meta), GFP_KERNEL);
 
 	if (!meta)
-- 
2.5.0

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#1205188

On (08/11/15 22:33), Sergey Senozhatsky wrote:
> zram_meta_alloc() constructs a pool name for zs_create_pool() call
> as
>  snprintf(pool_name, sizeof(pool_name), "zram%d", device_id);
> 
> However, it defines pool name buffer to be only 8 chars long
> (minus trailing zero), which means that we can have only 1000
> pool names: zram0 -- zram999.
> 
> With CONFIG_ZSMALLOC_STAT enabled an attempt to create a device
> zram1000 can fail if device zram100 already exists, because
> snprintf() will truncate new pool name to zram100 and pass it
> to debugfs_create_dir(), causing:
> 
>   debugfs dir <zram100> creation failed
>   zram: Error creating memory pool
> 
> ... and so on (zram101 - zram1010, etc).
> 
> Fix it by increasing pool_name buffer size to 11:

oh... don't know how this happened. to 15.

	-ss

> -- zram prefix (length 4)
> -- int device_id can use up to 10 chars
> -- terminating zero byte
> 
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> ---
>  drivers/block/zram/zram_drv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index b088ca9..1dec01d 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -502,7 +502,7 @@ static void zram_meta_free(struct zram_meta *meta, u64 disksize)
>  static struct zram_meta *zram_meta_alloc(int device_id, u64 disksize)
>  {
>  	size_t num_pages;
> -	char pool_name[8];
> +	char pool_name[15];
>  	struct zram_meta *meta = kmalloc(sizeof(*meta), GFP_KERNEL);
>  
>  	if (!meta)
> -- 
> 2.5.0
> 
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