[PATCH] md: allow md to load a superblock with feature-bit '1' set

As this is used to flag an internal bitmap.

Also, introduce symbolic names for feature bits.

Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 8 insertions, 3 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 866c704e008a..1be3f2de396b 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -875,7 +875,7 @@ static int super_1_load(mdk_rdev_t *rdev, mdk_rdev_t *refdev, int minor_version)
             sb->major_version != cpu_to_le32(1) ||
             le32_to_cpu(sb->max_dev) > (4096-256)/2 ||
             le64_to_cpu(sb->super_offset) != (rdev->sb_offset<<1) ||
-            sb->feature_map != 0)
+            (le32_to_cpu(sb->feature_map) & ~MD_FEATURE_ALL) != 0)
                 return -EINVAL;
 
         if (calc_sb_1_csum(sb) != sb->sb_csum) {
@@ -954,7 +954,7 @@ static int super_1_validate(mddev_t *mddev, mdk_rdev_t *rdev)
 
                 mddev->max_disks =  (4096-256)/2;
 
-                if ((le32_to_cpu(sb->feature_map) & 1) &&
+                if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_BITMAP_OFFSET) &&
                     mddev->bitmap_file == NULL ) {
                         if (mddev->level != 1) {
                                 printk(KERN_WARNING "md: bitmaps only supported for raid1\n");
@@ -1029,7 +1029,7 @@ static void super_1_sync(mddev_t *mddev, mdk_rdev_t *rdev)
 
         if (mddev->bitmap && mddev->bitmap_file == NULL) {
                 sb->bitmap_offset = cpu_to_le32((__u32)mddev->bitmap_offset);
-                sb->feature_map = cpu_to_le32(1);
+                sb->feature_map = cpu_to_le32(MD_FEATURE_BITMAP_OFFSET);
         }
 
         max_dev = 0;
diff --git a/include/linux/raid/md_p.h b/include/linux/raid/md_p.h
index 4f047f84fb1f..c100fa5d4bfa 100644
--- a/include/linux/raid/md_p.h
+++ b/include/linux/raid/md_p.h
@@ -238,5 +238,10 @@ struct mdp_superblock_1 {
         __u16   dev_roles[0];   /* role in array, or 0xffff for a spare, or 0xfffe for faulty */
 };
 
+/* feature_map bits */
+#define MD_FEATURE_BITMAP_OFFSET        1
+
+#define MD_FEATURE_ALL                  1
+
 #endif