This came about as part of auditing prandom_u32() usage, but
this is a special case: sometimes the starting value comes
from prandom_u32, and sometimes it comes from a hash of a name.
Does the name hash algorithm have to be stable? In that case, this
change would alter it. But it appears to use s_hash_seed which
is regenerated on "e2fsck -D", so maybe changing it isn't a big deal.
Feedback needed.
Signed-off-by: George Spelvin <lkml@xxxxxxx>
Cc: "Theodore Ts'o" <tytso@xxxxxxx>
Cc: Andreas Dilger <adilger.kernel@xxxxxxxxx>
Cc: linux-ext4@xxxxxxxxxxxxxxx
---
fs/ext4/ialloc.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 7db0c8814f2ec..a4ea89b3ed368 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -457,9 +457,8 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent,
grp = hinfo.hash;
} else
grp = prandom_u32();
- parent_group = (unsigned)grp % ngroups;
- for (i = 0; i < ngroups; i++) {
- g = (parent_group + i) % ngroups;
+ g = parent_group = reciprocal_scale(grp, ngroups);
+ for (i = 0; i < ngroups; i++, ++g == ngroups && (g = 0)) {
get_orlov_stats(sb, g, flex_size, &stats);
if (!stats.free_inodes)
continue;
--
2.26.0
