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ext4: use prandom_u32() instead of get_random_bytes()

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.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
master
Theodore Ts'o 8 years ago
parent
commit
dd1f723bf5
  1. 2
      fs/ext4/ialloc.c
  2. 2
      fs/ext4/mmp.c
  3. 7
      fs/ext4/super.c

2
fs/ext4/ialloc.c

@ -432,7 +432,7 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent,
ext4fs_dirhash(qstr->name, qstr->len, &hinfo);
grp = hinfo.hash;
} else
get_random_bytes(&grp, sizeof(grp));
grp = prandom_u32();
parent_group = (unsigned)grp % ngroups;
for (i = 0; i < ngroups; i++) {
g = (parent_group + i) % ngroups;

2
fs/ext4/mmp.c

@ -259,7 +259,7 @@ static unsigned int mmp_new_seq(void)
u32 new_seq;
do {
get_random_bytes(&new_seq, sizeof(u32));
new_seq = prandom_u32();
} while (new_seq > EXT4_MMP_SEQ_MAX);
return new_seq;

7
fs/ext4/super.c

@ -3068,7 +3068,6 @@ static struct ext4_li_request *ext4_li_request_new(struct super_block *sb,
{
struct ext4_sb_info *sbi = EXT4_SB(sb);
struct ext4_li_request *elr;
unsigned long rnd;
elr = kzalloc(sizeof(*elr), GFP_KERNEL);
if (!elr)
@ -3083,10 +3082,8 @@ static struct ext4_li_request *ext4_li_request_new(struct super_block *sb,
* spread the inode table initialization requests
* better.
*/
get_random_bytes(&rnd, sizeof(rnd));
elr->lr_next_sched = jiffies + (unsigned long)rnd %
(EXT4_DEF_LI_MAX_START_DELAY * HZ);
elr->lr_next_sched = jiffies + (prandom_u32() %
(EXT4_DEF_LI_MAX_START_DELAY * HZ));
return elr;
}

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