dm raid: round region_size to power of two

jbrassow · kergon · commit 3a0f9aaee028 · 2012-12-21T20:23:33.000Z
If the user does not supply a bitmap region_size to the dm raid target,
a reasonable size is computed automatically.  If this is not a power of 2,
the md code will report an error later.

This patch catches the problem early and rounds the region_size to the
next power of two.

Signed-off-by: Jonathan Brassow &lt;jbrassow@redhat.com&gt;
Signed-off-by: Alasdair G Kergon &lt;agk@redhat.com&gt;
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
@@ -295,9 +295,11 @@ static int validate_region_size(struct raid_set *rs, unsigned long region_size)
 		 * Choose a reasonable default.  All figures in sectors.
 		 */
 		if (min_region_size > (1 << 13)) {
+			/* If not a power of 2, make it the next power of 2 */
+			if (min_region_size & (min_region_size - 1))
+				region_size = 1 << fls(region_size);
 			DMINFO("Choosing default region size of %lu sectors",
 			       region_size);
-			region_size = min_region_size;
 		} else {
 			DMINFO("Choosing default region size of 4MiB");
 			region_size = 1 << 13; /* sectors */
