[PATCH] md: make md on-disk bitmaps not host-endian

Current bitmaps use set_bit et.al and so are host-endian, which means
not-portable.  Oops.

Define a new version number (4) for which bitmaps are little-endian.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 31 insertions, 8 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index c5fa4c2a5af1..220273e81ed6 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -482,7 +482,8 @@ static int bitmap_read_sb(struct bitmap *bitmap)
         /* verify that the bitmap-specific fields are valid */
         if (sb->magic != cpu_to_le32(BITMAP_MAGIC))
                 reason = "bad magic";
-        else if (sb->version != cpu_to_le32(BITMAP_MAJOR))
+        else if (le32_to_cpu(sb->version) < BITMAP_MAJOR_LO ||
+                 le32_to_cpu(sb->version) > BITMAP_MAJOR_HI)
                 reason = "unrecognized superblock version";
         else if (chunksize < 512 || chunksize > (1024 * 1024 * 4))
                 reason = "bitmap chunksize out of range (512B - 4MB)";
@@ -527,6 +528,8 @@ success:
         bitmap->daemon_lastrun = jiffies;
         bitmap->max_write_behind = write_behind;
         bitmap->flags |= sb->state;
+        if (le32_to_cpu(sb->version) == BITMAP_MAJOR_HOSTENDIAN)
+                bitmap->flags |= BITMAP_HOSTENDIAN;
         bitmap->events_cleared = le64_to_cpu(sb->events_cleared);
         if (sb->state & BITMAP_STALE)
                 bitmap->events_cleared = bitmap->mddev->events;
@@ -764,7 +767,10 @@ static void bitmap_file_set_bit(struct bitmap *bitmap, sector_t block)
 
         /* set the bit */
         kaddr = kmap_atomic(page, KM_USER0);
-        set_bit(bit, kaddr);
+        if (bitmap->flags & BITMAP_HOSTENDIAN)
+                set_bit(bit, kaddr);
+        else
+                ext2_set_bit(bit, kaddr);
         kunmap_atomic(kaddr, KM_USER0);
         PRINTK("set file bit %lu page %lu\n", bit, page->index);
 
@@ -891,6 +897,7 @@ static int bitmap_init_from_disk(struct bitmap *bitmap, sector_t start)
         oldindex = ~0L;
 
         for (i = 0; i < chunks; i++) {
+                int b;
                 index = file_page_index(i);
                 bit = file_page_offset(i);
                 if (index != oldindex) { /* this is a new page, read it in */
@@ -939,7 +946,11 @@ static int bitmap_init_from_disk(struct bitmap *bitmap, sector_t start)
 
                         bitmap->filemap[bitmap->file_pages++] = page;
                 }
-                if (test_bit(bit, page_address(page))) {
+                if (bitmap->flags & BITMAP_HOSTENDIAN)
+                        b = test_bit(bit, page_address(page));
+                else
+                        b = ext2_test_bit(bit, page_address(page));
+                if (b) {
                         /* if the disk bit is set, set the memory bit */
                         bitmap_set_memory_bits(bitmap, i << CHUNK_BLOCK_SHIFT(bitmap),
                                                ((i+1) << (CHUNK_BLOCK_SHIFT(bitmap)) >= start)
@@ -1097,7 +1108,10 @@ int bitmap_daemon_work(struct bitmap *bitmap)
                                                   -1);
 
                                 /* clear the bit */
-                                clear_bit(file_page_offset(j), page_address(page));
+                                if (bitmap->flags & BITMAP_HOSTENDIAN)
+                                        clear_bit(file_page_offset(j), page_address(page));
+                                else
+                                        ext2_clear_bit(file_page_offset(j), page_address(page));
                         }
                 }
                 spin_unlock_irqrestore(&bitmap->lock, flags);
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 9dfa063d1c6a..caa4add00c1b 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4281,7 +4281,7 @@ static int __init md_init(void)
                         " MD_SB_DISKS=%d\n",
                         MD_MAJOR_VERSION, MD_MINOR_VERSION,
                         MD_PATCHLEVEL_VERSION, MAX_MD_DEVS, MD_SB_DISKS);
-        printk(KERN_INFO "md: bitmap version %d.%d\n", BITMAP_MAJOR,
+        printk(KERN_INFO "md: bitmap version %d.%d\n", BITMAP_MAJOR_HI,
                         BITMAP_MINOR);
 
         if (register_blkdev(MAJOR_NR, "md"))
diff --git a/include/linux/raid/bitmap.h b/include/linux/raid/bitmap.h
index 9de99198caf1..899437802aea 100644
--- a/include/linux/raid/bitmap.h
+++ b/include/linux/raid/bitmap.h
@@ -6,7 +6,13 @@
 #ifndef BITMAP_H
 #define BITMAP_H 1
 
-#define BITMAP_MAJOR 3
+#define BITMAP_MAJOR_LO 3
+/* version 4 insists the bitmap is in little-endian order
+ * with version 3, it is host-endian which is non-portable
+ */
+#define BITMAP_MAJOR_HI 4
+#define BITMAP_MAJOR_HOSTENDIAN 3
+
 #define BITMAP_MINOR 39
 
 /*
@@ -133,7 +139,8 @@ typedef __u16 bitmap_counter_t;
 /* use these for bitmap->flags and bitmap->sb->state bit-fields */
 enum bitmap_state {
         BITMAP_ACTIVE = 0x001, /* the bitmap is in use */
-        BITMAP_STALE  = 0x002  /* the bitmap file is out of date or had -EIO */
+        BITMAP_STALE  = 0x002,  /* the bitmap file is out of date or had -EIO */
+        BITMAP_HOSTENDIAN = 0x8000,
 };
 
 /* the superblock at the front of the bitmap file -- little endian */
diff --git a/include/linux/raid/md.h b/include/linux/raid/md.h
index ffa316ce4dc8..91467a3c4a52 100644
--- a/include/linux/raid/md.h
+++ b/include/linux/raid/md.h
@@ -66,8 +66,10 @@
  *     and major_version/minor_version accordingly
  * >=2 means that Internal bitmaps are supported by setting MD_SB_BITMAP_PRESENT
  *     in the super status byte
+ * >=3 means that bitmap superblock version 4 is supported, which uses
+ *     little-ending representation rather than host-endian
  */
-#define MD_PATCHLEVEL_VERSION           2
+#define MD_PATCHLEVEL_VERSION           3
 
 extern int register_md_personality (int p_num, mdk_personality_t *p);
 extern int unregister_md_personality (int p_num);