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Commit dd1f723b authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

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: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent f2754114

fs/ext4/ialloc.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

fs/ext4/mmp.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

fs/ext4/super.c

+2 −5
Original line number Diff line number Diff line
@@ -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;

}