Btrfs: superblock duplication
This patch implements superblock duplication. Superblocks
are stored at offset 16K, 64M and 256G on every devices.
Spaces used by superblocks are preserved by the allocator,
which uses a reverse mapping function to find the logical
addresses that correspond to superblocks. Thank you,
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 61dc3b2..c72f4f3 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1595,8 +1595,7 @@
fs_info, BTRFS_ROOT_TREE_OBJECTID);
- bh = __bread(fs_devices->latest_bdev,
- BTRFS_SUPER_INFO_OFFSET / 4096, 4096);
+ bh = btrfs_read_dev_super(fs_devices->latest_bdev);
if (!bh)
goto fail_iput;
@@ -1710,7 +1709,7 @@
}
mutex_lock(&fs_info->chunk_mutex);
- ret = btrfs_read_sys_array(tree_root);
+ ret = btrfs_read_sys_array(tree_root, btrfs_super_bytenr(disk_super));
mutex_unlock(&fs_info->chunk_mutex);
if (ret) {
printk("btrfs: failed to read the system array on %s\n",
@@ -1905,19 +1904,147 @@
put_bh(bh);
}
-static int write_all_supers(struct btrfs_root *root)
+struct buffer_head *btrfs_read_dev_super(struct block_device *bdev)
+{
+ struct buffer_head *bh;
+ struct buffer_head *latest = NULL;
+ struct btrfs_super_block *super;
+ int i;
+ u64 transid = 0;
+ u64 bytenr;
+
+ /* we would like to check all the supers, but that would make
+ * a btrfs mount succeed after a mkfs from a different FS.
+ * So, we need to add a special mount option to scan for
+ * later supers, using BTRFS_SUPER_MIRROR_MAX instead
+ */
+ for (i = 0; i < 1; i++) {
+ bytenr = btrfs_sb_offset(i);
+ if (bytenr + 4096 >= i_size_read(bdev->bd_inode))
+ break;
+ bh = __bread(bdev, bytenr / 4096, 4096);
+ if (!bh)
+ continue;
+
+ super = (struct btrfs_super_block *)bh->b_data;
+ if (btrfs_super_bytenr(super) != bytenr ||
+ strncmp((char *)(&super->magic), BTRFS_MAGIC,
+ sizeof(super->magic))) {
+ brelse(bh);
+ continue;
+ }
+
+ if (!latest || btrfs_super_generation(super) > transid) {
+ brelse(latest);
+ latest = bh;
+ transid = btrfs_super_generation(super);
+ } else {
+ brelse(bh);
+ }
+ }
+ return latest;
+}
+
+static int write_dev_supers(struct btrfs_device *device,
+ struct btrfs_super_block *sb,
+ int do_barriers, int wait, int max_mirrors)
+{
+ struct buffer_head *bh;
+ int i;
+ int ret;
+ int errors = 0;
+ u32 crc;
+ u64 bytenr;
+ int last_barrier = 0;
+
+ if (max_mirrors == 0)
+ max_mirrors = BTRFS_SUPER_MIRROR_MAX;
+
+ /* make sure only the last submit_bh does a barrier */
+ if (do_barriers) {
+ for (i = 0; i < max_mirrors; i++) {
+ bytenr = btrfs_sb_offset(i);
+ if (bytenr + BTRFS_SUPER_INFO_SIZE >=
+ device->total_bytes)
+ break;
+ last_barrier = i;
+ }
+ }
+
+ for (i = 0; i < max_mirrors; i++) {
+ bytenr = btrfs_sb_offset(i);
+ if (bytenr + BTRFS_SUPER_INFO_SIZE >= device->total_bytes)
+ break;
+
+ if (wait) {
+ bh = __find_get_block(device->bdev, bytenr / 4096,
+ BTRFS_SUPER_INFO_SIZE);
+ BUG_ON(!bh);
+ brelse(bh);
+ wait_on_buffer(bh);
+ if (buffer_uptodate(bh)) {
+ brelse(bh);
+ continue;
+ }
+ } else {
+ btrfs_set_super_bytenr(sb, bytenr);
+
+ crc = ~(u32)0;
+ crc = btrfs_csum_data(NULL, (char *)sb +
+ BTRFS_CSUM_SIZE, crc,
+ BTRFS_SUPER_INFO_SIZE -
+ BTRFS_CSUM_SIZE);
+ btrfs_csum_final(crc, sb->csum);
+
+ bh = __getblk(device->bdev, bytenr / 4096,
+ BTRFS_SUPER_INFO_SIZE);
+ memcpy(bh->b_data, sb, BTRFS_SUPER_INFO_SIZE);
+
+ set_buffer_uptodate(bh);
+ get_bh(bh);
+ lock_buffer(bh);
+ bh->b_end_io = btrfs_end_buffer_write_sync;
+ }
+
+ if (i == last_barrier && do_barriers && device->barriers) {
+ ret = submit_bh(WRITE_BARRIER, bh);
+ if (ret == -EOPNOTSUPP) {
+ printk("btrfs: disabling barriers on dev %s\n",
+ device->name);
+ set_buffer_uptodate(bh);
+ device->barriers = 0;
+ get_bh(bh);
+ lock_buffer(bh);
+ ret = submit_bh(WRITE, bh);
+ }
+ } else {
+ ret = submit_bh(WRITE, bh);
+ }
+
+ if (!ret && wait) {
+ wait_on_buffer(bh);
+ if (!buffer_uptodate(bh))
+ errors++;
+ } else if (ret) {
+ errors++;
+ }
+ if (wait)
+ brelse(bh);
+ }
+ return errors < i ? 0 : -1;
+}
+
+int write_all_supers(struct btrfs_root *root, int max_mirrors)
{
struct list_head *cur;
struct list_head *head = &root->fs_info->fs_devices->devices;
struct btrfs_device *dev;
struct btrfs_super_block *sb;
struct btrfs_dev_item *dev_item;
- struct buffer_head *bh;
int ret;
int do_barriers;
int max_errors;
int total_errors = 0;
- u32 crc;
u64 flags;
max_errors = btrfs_super_num_devices(&root->fs_info->super_copy) - 1;
@@ -1944,40 +2071,11 @@
btrfs_set_stack_device_sector_size(dev_item, dev->sector_size);
memcpy(dev_item->uuid, dev->uuid, BTRFS_UUID_SIZE);
memcpy(dev_item->fsid, dev->fs_devices->fsid, BTRFS_UUID_SIZE);
+
flags = btrfs_super_flags(sb);
btrfs_set_super_flags(sb, flags | BTRFS_HEADER_FLAG_WRITTEN);
-
- crc = ~(u32)0;
- crc = btrfs_csum_data(root, (char *)sb + BTRFS_CSUM_SIZE, crc,
- BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
- btrfs_csum_final(crc, sb->csum);
-
- bh = __getblk(dev->bdev, BTRFS_SUPER_INFO_OFFSET / 4096,
- BTRFS_SUPER_INFO_SIZE);
-
- memcpy(bh->b_data, sb, BTRFS_SUPER_INFO_SIZE);
- dev->pending_io = bh;
-
- get_bh(bh);
- set_buffer_uptodate(bh);
- lock_buffer(bh);
- bh->b_end_io = btrfs_end_buffer_write_sync;
-
- if (do_barriers && dev->barriers) {
- ret = submit_bh(WRITE_BARRIER, bh);
- if (ret == -EOPNOTSUPP) {
- printk("btrfs: disabling barriers on dev %s\n",
- dev->name);
- set_buffer_uptodate(bh);
- dev->barriers = 0;
- get_bh(bh);
- lock_buffer(bh);
- ret = submit_bh(WRITE, bh);
- }
- } else {
- ret = submit_bh(WRITE, bh);
- }
+ ret = write_dev_supers(dev, sb, do_barriers, 0, max_mirrors);
if (ret)
total_errors++;
}
@@ -1985,8 +2083,8 @@
printk("btrfs: %d errors while writing supers\n", total_errors);
BUG();
}
- total_errors = 0;
+ total_errors = 0;
list_for_each(cur, head) {
dev = list_entry(cur, struct btrfs_device, dev_list);
if (!dev->bdev)
@@ -1994,29 +2092,9 @@
if (!dev->in_fs_metadata || !dev->writeable)
continue;
- BUG_ON(!dev->pending_io);
- bh = dev->pending_io;
- wait_on_buffer(bh);
- if (!buffer_uptodate(dev->pending_io)) {
- if (do_barriers && dev->barriers) {
- printk("btrfs: disabling barriers on dev %s\n",
- dev->name);
- set_buffer_uptodate(bh);
- get_bh(bh);
- lock_buffer(bh);
- dev->barriers = 0;
- ret = submit_bh(WRITE, bh);
- BUG_ON(ret);
- wait_on_buffer(bh);
- if (!buffer_uptodate(bh))
- total_errors++;
- } else {
- total_errors++;
- }
-
- }
- dev->pending_io = NULL;
- brelse(bh);
+ ret = write_dev_supers(dev, sb, do_barriers, 1, max_mirrors);
+ if (ret)
+ total_errors++;
}
if (total_errors > max_errors) {
printk("btrfs: %d errors while writing supers\n", total_errors);
@@ -2025,12 +2103,12 @@
return 0;
}
-int write_ctree_super(struct btrfs_trans_handle *trans, struct btrfs_root
- *root)
+int write_ctree_super(struct btrfs_trans_handle *trans,
+ struct btrfs_root *root, int max_mirrors)
{
int ret;
- ret = write_all_supers(root);
+ ret = write_all_supers(root, max_mirrors);
return ret;
}
@@ -2116,7 +2194,7 @@
ret = btrfs_write_and_wait_transaction(NULL, root);
BUG_ON(ret);
- ret = write_ctree_super(NULL, root);
+ ret = write_ctree_super(NULL, root, 0);
return ret;
}