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>

diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 137193ff389b88510f414499116c8a9ee858abe5..0ee59a6644e211b752480364c95e5616ab9e92fd 100644 (file)
--- a/fs/ext4/ialloc.c
+++ b/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;

diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c
index 214461e42a05c8be0374224c81c2a549135b7014..04434ad3e8e0115785c653e1815bc9518563bbc7 100644 (file)
--- a/fs/ext4/mmp.c
+++ b/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;

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index d3a857bfae47631db0ab56f765f1028a244261ea..c977f4e4e63be6c4cf3b477f628e4fc7d323d1f5 100644 (file)
--- a/fs/ext4/super.c
+++ b/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;
 }