[PATCH] ext2/3: use prandom_u32() instead of get_random_bytes()

[PATCH] ext2/3: use prandom_u32() instead of get_random_bytes()

[ZhangZhen]

Many of the uses of get_random_bytes() do not actually need
cryptographically secure random numbers.  Replace those uses with a
call to prandom_u32(), which is faster and which doesn't consume
entropy from the /dev/random driver.

The commit dd1f723bf56bd96efc9d90e9e60dc511c79de48f has made that for
ext4, and i did the same for ext2/3.

Signed-off-by: Zhang Zhen <zhenzhang.zhang@huawei.com>
---
 fs/ext2/ialloc.c | 2 +-
 fs/ext3/ialloc.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext2/ialloc.c b/fs/ext2/ialloc.c
index 7cadd82..32f131a 100644
--- a/fs/ext2/ialloc.c
+++ b/fs/ext2/ialloc.c
@@ -284,7 +284,7 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent)
 		int best_ndir = inodes_per_group;
 		int best_group = -1;

-		get_random_bytes(&group, sizeof(group));
+		grp = prandom_u32();
 		parent_group = (unsigned)group % ngroups;
 		for (i = 0; i < ngroups; i++) {
 			group = (parent_group + i) % ngroups;
diff --git a/fs/ext3/ialloc.c b/fs/ext3/ialloc.c
index 082afd7..60e63e3 100644
--- a/fs/ext3/ialloc.c
+++ b/fs/ext3/ialloc.c
@@ -215,7 +215,7 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent)
 		int best_ndir = inodes_per_group;
 		int best_group = -1;

-		get_random_bytes(&group, sizeof(group));
+		grp = prandom_u32();
 		parent_group = (unsigned)group % ngroups;
 		for (i = 0; i < ngroups; i++) {
 			group = (parent_group + i) % ngroups;
-- 
1.8.1.4


.

Re: [PATCH] ext2/3: use prandom_u32() instead of get_random_bytes()

[Jan Kara]

On Wed 26-02-14 10:32:41, ZhangZhen wrote:
> Many of the uses of get_random_bytes() do not actually need
> cryptographically secure random numbers.  Replace those uses with a
> call to prandom_u32(), which is faster and which doesn't consume
> entropy from the /dev/random driver.
> 
> The commit dd1f723bf56bd96efc9d90e9e60dc511c79de48f has made that for
> ext4, and i did the same for ext2/3.
  Thanks. I've merged the patch to my tree.

								Honza

> 
> Signed-off-by: Zhang Zhen <zhenzhang.zhang@huawei.com>
> ---
>  fs/ext2/ialloc.c | 2 +-
>  fs/ext3/ialloc.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext2/ialloc.c b/fs/ext2/ialloc.c
> index 7cadd82..32f131a 100644
> --- a/fs/ext2/ialloc.c
> +++ b/fs/ext2/ialloc.c
> @@ -284,7 +284,7 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent)
>  		int best_ndir = inodes_per_group;
>  		int best_group = -1;
> 
> -		get_random_bytes(&group, sizeof(group));
> +		grp = prandom_u32();
>  		parent_group = (unsigned)group % ngroups;
>  		for (i = 0; i < ngroups; i++) {
>  			group = (parent_group + i) % ngroups;
> diff --git a/fs/ext3/ialloc.c b/fs/ext3/ialloc.c
> index 082afd7..60e63e3 100644
> --- a/fs/ext3/ialloc.c
> +++ b/fs/ext3/ialloc.c
> @@ -215,7 +215,7 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent)
>  		int best_ndir = inodes_per_group;
>  		int best_group = -1;
> 
> -		get_random_bytes(&group, sizeof(group));
> +		grp = prandom_u32();
>  		parent_group = (unsigned)group % ngroups;
>  		for (i = 0; i < ngroups; i++) {
>  			group = (parent_group + i) % ngroups;
> -- 
> 1.8.1.4
> 
> 
> .
> 
> 
> 
> 
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR