[PATCH] md: allow md intent bitmap to be stored near the superblock.

This provides an alternate to storing the bitmap in a separate file.  The
bitmap can be stored at a given offset from the superblock.  Obviously the
creator of the array must make sure this doesn't intersect with data....
After is good for version-0.90 superblocks.

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>

4 files changed, 26 insertions, 2 deletions

diff --git a/include/linux/raid/bitmap.h b/include/linux/raid/bitmap.h
index cfe60cf..e24b74b 100644
--- a/include/linux/raid/bitmap.h
+++ b/include/linux/raid/bitmap.h
@@ -217,6 +217,7 @@ struct bitmap {
 	/* bitmap spinlock */
 	spinlock_t lock;
 
+	long offset; /* offset from superblock if file is NULL */
 	struct file *file; /* backing disk file */
 	struct page *sb_page; /* cached copy of the bitmap file superblock */
 	struct page **filemap; /* list of cache pages for the file */
@@ -255,6 +256,7 @@ void bitmap_print_sb(struct bitmap *bitmap);
 int bitmap_update_sb(struct bitmap *bitmap);
 
 int  bitmap_setallbits(struct bitmap *bitmap);
+void bitmap_write_all(struct bitmap *bitmap);
 
 /* these are exported */
 int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors);
diff --git a/include/linux/raid/md.h b/include/linux/raid/md.h
index 75f41d8..ffa316c 100644
--- a/include/linux/raid/md.h
+++ b/include/linux/raid/md.h
@@ -60,7 +60,14 @@
  */
 #define MD_MAJOR_VERSION                0
 #define MD_MINOR_VERSION                90
-#define MD_PATCHLEVEL_VERSION           1
+/*
+ * MD_PATCHLEVEL_VERSION indicates kernel functionality.
+ * >=1 means different superblock formats are selectable using SET_ARRAY_INFO
+ *     and major_version/minor_version accordingly
+ * >=2 means that Internal bitmaps are supported by setting MD_SB_BITMAP_PRESENT
+ *     in the super status byte
+ */
+#define MD_PATCHLEVEL_VERSION           2
 
 extern int register_md_personality (int p_num, mdk_personality_t *p);
 extern int unregister_md_personality (int p_num);
@@ -78,6 +85,12 @@ extern void md_unplug_mddev(mddev_t *mddev);
 
 extern void md_print_devices (void);
 
+extern void md_super_write(mddev_t *mddev, mdk_rdev_t *rdev,
+			   sector_t sector, int size, struct page *page);
+extern int sync_page_io(struct block_device *bdev, sector_t sector, int size,
+			struct page *page, int rw);
+
+
 #define MD_BUG(x...) { printk("md: bug in file %s, line %d\n", __FILE__, __LINE__); md_print_devices(); }
 
 #endif 
diff --git a/include/linux/raid/md_k.h b/include/linux/raid/md_k.h
index 3e97702..a3725b57 100644
--- a/include/linux/raid/md_k.h
+++ b/include/linux/raid/md_k.h
@@ -273,6 +273,10 @@ struct mddev_s
 
 	struct bitmap                   *bitmap; /* the bitmap for the device */
 	struct file			*bitmap_file; /* the bitmap file */
+	long				bitmap_offset; /* offset from superblock of
+							* start of bitmap. May be
+							* negative, but not '0'
+							*/
 
 	struct list_head		all_mddevs;
 };
diff --git a/include/linux/raid/md_p.h b/include/linux/raid/md_p.h
index 8ba95d6..8e592a2 100644
--- a/include/linux/raid/md_p.h
+++ b/include/linux/raid/md_p.h
@@ -96,6 +96,7 @@ typedef struct mdp_device_descriptor_s {
 #define MD_SB_CLEAN		0
 #define MD_SB_ERRORS		1
 
+#define	MD_SB_BITMAP_PRESENT	8 /* bitmap may be present nearby */
 typedef struct mdp_superblock_s {
 	/*
 	 * Constant generic information
@@ -184,7 +185,7 @@ struct mdp_superblock_1 {
 	/* constant array information - 128 bytes */
 	__u32	magic;		/* MD_SB_MAGIC: 0xa92b4efc - little endian */
 	__u32	major_version;	/* 1 */
-	__u32	feature_map;	/* 0 for now */
+	__u32	feature_map;	/* bit 0 set if 'bitmap_offset' is meaningful */
 	__u32	pad0;		/* always set to 0 when writing */
 
 	__u8	set_uuid[16];	/* user-space generated. */
@@ -197,6 +198,10 @@ struct mdp_superblock_1 {
 
 	__u32	chunksize;	/* in 512byte sectors */
 	__u32	raid_disks;
+	__u32	bitmap_offset;	/* sectors after start of superblock that bitmap starts
+				 * NOTE: signed, so bitmap can be before superblock
+				 * only meaningful of feature_map[0] is set.
+				 */
 	__u8	pad1[128-96];	/* set to 0 when written */
 
 	/* constant this-device information - 64 bytes */