Btrfs: add btrfs_read_dev_one_super() to read one specific SB
This uses a chunk of code from btrfs_read_dev_super() and creates
a function called btrfs_read_dev_one_super() so that next patch
can use it for scratch superblock.
Signed-off-by: Anand Jain <anand.jain@oracle.com>
[renamed bufhead to bh]
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 0f8e33f..c7c739f 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3188,6 +3188,37 @@
put_bh(bh);
}
+int btrfs_read_dev_one_super(struct block_device *bdev, int copy_num,
+ struct buffer_head **bh_ret)
+{
+ struct buffer_head *bh;
+ struct btrfs_super_block *super;
+ u64 bytenr;
+
+ bytenr = btrfs_sb_offset(copy_num);
+ if (bytenr + BTRFS_SUPER_INFO_SIZE >= i_size_read(bdev->bd_inode))
+ return -EINVAL;
+
+ bh = __bread(bdev, bytenr / 4096, BTRFS_SUPER_INFO_SIZE);
+ /*
+ * If we fail to read from the underlying devices, as of now
+ * the best option we have is to mark it EIO.
+ */
+ if (!bh)
+ return -EIO;
+
+ super = (struct btrfs_super_block *)bh->b_data;
+ if (btrfs_super_bytenr(super) != bytenr ||
+ btrfs_super_magic(super) != BTRFS_MAGIC) {
+ brelse(bh);
+ return -EINVAL;
+ }
+
+ *bh_ret = bh;
+ return 0;
+}
+
+
struct buffer_head *btrfs_read_dev_super(struct block_device *bdev)
{
struct buffer_head *bh;
@@ -3195,7 +3226,6 @@
struct btrfs_super_block *super;
int i;
u64 transid = 0;
- u64 bytenr;
int ret = -EINVAL;
/* we would like to check all the supers, but that would make
@@ -3204,28 +3234,11 @@
* later supers, using BTRFS_SUPER_MIRROR_MAX instead
*/
for (i = 0; i < 1; i++) {
- bytenr = btrfs_sb_offset(i);
- if (bytenr + BTRFS_SUPER_INFO_SIZE >=
- i_size_read(bdev->bd_inode))
- break;
- bh = __bread(bdev, bytenr / 4096,
- BTRFS_SUPER_INFO_SIZE);
- /*
- * If we fail to read from the underlying devices, as of now
- * the best option we have is to mark it EIO.
- */
- if (!bh) {
- ret = -EIO;
+ ret = btrfs_read_dev_one_super(bdev, i, &bh);
+ if (ret)
continue;
- }
super = (struct btrfs_super_block *)bh->b_data;
- if (btrfs_super_bytenr(super) != bytenr ||
- btrfs_super_magic(super) != BTRFS_MAGIC) {
- brelse(bh);
- ret = -EINVAL;
- continue;
- }
if (!latest || btrfs_super_generation(super) > transid) {
brelse(latest);