Patch name: md-separate-meta-and-data-devs.patch
Allow the metadata to be on a separate device from the
data.
This doesn't mean the data and metadata will by on separate
physical devices - it simply gives device-mapper and userspace
tools more flexibility.
RFC-by: Jonathan Brassow <jbrassow@xxxxxxxxxx>
Index: linux-2.6/drivers/md/bitmap.c
===================================================================
--- linux-2.6.orig/drivers/md/bitmap.c
+++ linux-2.6/drivers/md/bitmap.c
@@ -263,14 +263,18 @@ static mdk_rdev_t *next_active_rdev(mdk_
static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
{
mdk_rdev_t *rdev = NULL;
+ struct block_device *bdev;
mddev_t *mddev = bitmap->mddev;
while ((rdev = next_active_rdev(rdev, mddev)) != NULL) {
int size = PAGE_SIZE;
loff_t offset = mddev->bitmap_info.offset;
+
+ bdev = (rdev->meta_bdev) ? rdev->meta_bdev : rdev->bdev;
+
if (page->index == bitmap->file_pages-1)
size = roundup(bitmap->last_page_size,
- bdev_logical_block_size(rdev->bdev));
+ bdev_logical_block_size(bdev));
/* Just make sure we aren't corrupting data or
* metadata
*/
Index: linux-2.6/drivers/md/md.c
===================================================================
--- linux-2.6.orig/drivers/md/md.c
+++ linux-2.6/drivers/md/md.c
@@ -707,6 +707,20 @@ static struct mdk_personality *find_pers
static inline sector_t calc_dev_sboffset(mdk_rdev_t *rdev)
{
sector_t num_sectors = i_size_read(rdev->bdev->bd_inode) / 512;
+
+ if (rdev->meta_bdev)
+ return 0;
+
+ return MD_NEW_SIZE_SECTORS(num_sectors);
+}
+
+static inline sector_t calc_dev_sectors(mdk_rdev_t *rdev)
+{
+ sector_t num_sectors = i_size_read(rdev->bdev->bd_inode) / 512;
+
+ if (rdev->meta_bdev)
+ return num_sectors;
+
return MD_NEW_SIZE_SECTORS(num_sectors);
}
@@ -764,7 +778,7 @@ void md_super_write(mddev_t *mddev, mdk_
*/
struct bio *bio = bio_alloc_mddev(GFP_NOIO, 1, mddev);
- bio->bi_bdev = rdev->bdev;
+ bio->bi_bdev = (rdev->meta_bdev) ? rdev->meta_bdev : rdev->bdev;
bio->bi_sector = sector;
bio_add_page(bio, page, size, 0);
bio->bi_private = rdev;
@@ -802,7 +816,8 @@ int sync_page_io(mdk_rdev_t *rdev, secto
rw |= REQ_SYNC | REQ_UNPLUG;
- bio->bi_bdev = rdev->bdev;
+ bio->bi_bdev = (metadata_op && rdev->meta_bdev) ?
+ rdev->meta_bdev : rdev->bdev;
bio->bi_sector = sector;
bio_add_page(bio, page, size, 0);
init_completion(&event);
@@ -820,6 +835,7 @@ EXPORT_SYMBOL_GPL(sync_page_io);
static int read_disk_sb(mdk_rdev_t * rdev, int size)
{
char b[BDEVNAME_SIZE];
+
if (!rdev->sb_page) {
MD_BUG();
return -EINVAL;
@@ -1678,7 +1694,7 @@ super_1_rdev_size_change(mdk_rdev_t *rde
sector_t max_sectors;
if (num_sectors && num_sectors < rdev->mddev->dev_sectors)
return 0; /* component must fit device */
- if (rdev->sb_start < rdev->data_offset) {
+ if (rdev->meta_bdev || rdev->sb_start < rdev->data_offset) {
/* minor versions 1 and 2; superblock before data */
max_sectors = i_size_read(rdev->bdev->bd_inode) >> 9;
max_sectors -= rdev->data_offset;
@@ -1769,6 +1785,7 @@ int md_integrity_register(mddev_t *mddev
* If at least one rdev is not integrity capable, we can not
* enable data integrity for the md device.
*/
+ /* FIXME (brassow): check both [meta_]bdev ? */
if (!bdev_get_integrity(rdev->bdev))
return -EINVAL;
if (!reference) {
@@ -1935,6 +1952,8 @@ static int lock_rdev(mdk_rdev_t *rdev, d
struct block_device *bdev;
char b[BDEVNAME_SIZE];
+ /* FIXME (brassow): [un]lock all both [meta_]bdev ? */
+
bdev = open_by_devnum(dev, FMODE_READ|FMODE_WRITE);
if (IS_ERR(bdev)) {
printk(KERN_ERR "md: could not open %s.\n",
@@ -1957,6 +1976,8 @@ static int lock_rdev(mdk_rdev_t *rdev, d
static void unlock_rdev(mdk_rdev_t *rdev)
{
struct block_device *bdev = rdev->bdev;
+
+ /* FIXME brassow: end here on 'bdev' search */
rdev->bdev = NULL;
if (!bdev)
MD_BUG();
@@ -4434,7 +4455,18 @@ int md_run(mddev_t *mddev)
* We don't want the data to overlap the metadata,
* Internal Bitmap issues have been handled elsewhere.
*/
- if (rdev->data_offset < rdev->sb_start) {
+ if (rdev->meta_bdev) {
+ /* Metadata is on a separate device */
+ if (rdev->data_offset) {
+ printk(KERN_ERR "md: data_offset should be 0\n");
+ return -EINVAL;
+ }
+
+ if (rdev->sb_start) {
+ printk(KERN_ERR "md: sb_start should be 0\n");
+ return -EINVAL;
+ }
+ } else if (rdev->data_offset < rdev->sb_start) {
if (mddev->dev_sectors &&
rdev->data_offset + mddev->dev_sectors
> rdev->sb_start) {
@@ -5240,7 +5272,7 @@ static int add_new_disk(mddev_t * mddev,
rdev->sb_start = i_size_read(rdev->bdev->bd_inode) / 512;
} else
rdev->sb_start = calc_dev_sboffset(rdev);
- rdev->sectors = rdev->sb_start;
+ rdev->sectors = calc_dev_sectors(rdev);
err = bind_rdev_to_array(rdev, mddev);
if (err) {
@@ -5310,7 +5342,7 @@ static int hot_add_disk(mddev_t * mddev,
else
rdev->sb_start = i_size_read(rdev->bdev->bd_inode) / 512;
- rdev->sectors = rdev->sb_start;
+ rdev->sectors = calc_dev_sectors(rdev);
if (test_bit(Faulty, &rdev->flags)) {
printk(KERN_WARNING
@@ -5519,7 +5551,6 @@ static int update_size(mddev_t *mddev, s
* sb_start or, if that is <data_offset, it must fit before the size
* of each device. If num_sectors is zero, we find the largest size
* that fits.
-
*/
if (mddev->sync_thread)
return -EBUSY;
Index: linux-2.6/drivers/md/md.h
===================================================================
--- linux-2.6.orig/drivers/md/md.h
+++ linux-2.6/drivers/md/md.h
@@ -60,6 +60,12 @@ struct mdk_rdev_s
mddev_t *mddev; /* RAID array if running */
int last_events; /* IO event timestamp */
+ /*
+ * If meta_bdev is non-NULL, it means that a separate device is
+ * being used to store the metadata (superblock/bitmap) which
+ * would otherwise be contained on the same device as the data (bdev).
+ */
+ struct block_device *meta_bdev;
struct block_device *bdev; /* block device handle */
struct page *sb_page;
--
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