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Commit 29c36d72 authored by Anand Jain's avatar Anand Jain Committed by David Sterba
Browse files

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: default avatarAnand Jain <anand.jain@oracle.com>
[renamed bufhead to bh]
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent d74a6259

fs/btrfs/disk-io.c

+33 −20
Original line number Diff line number Diff line
@@ -3188,6 +3188,37 @@ static void btrfs_end_buffer_write_sync(struct buffer_head *bh, int uptodate) 
	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 buffer_head *btrfs_read_dev_super(struct block_device *bdev) 
	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 @@ struct buffer_head *btrfs_read_dev_super(struct block_device *bdev) 
	 * 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);

fs/btrfs/disk-io.h

+2 −0
Original line number Diff line number Diff line
@@ -60,6 +60,8 @@ void close_ctree(struct btrfs_root *root); 
int write_ctree_super(struct btrfs_trans_handle *trans,

		      struct btrfs_root *root, int max_mirrors);

struct buffer_head *btrfs_read_dev_super(struct block_device *bdev);

int btrfs_read_dev_one_super(struct block_device *bdev, int copy_num,

			struct buffer_head **bh_ret);

int btrfs_commit_super(struct btrfs_root *root);

struct extent_buffer *btrfs_find_tree_block(struct btrfs_fs_info *fs_info,

					    u64 bytenr);