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>
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@ -3188,6 +3188,37 @@ static void btrfs_end_buffer_write_sync(struct buffer_head *bh, int uptodate)
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put_bh(bh);
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}
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int btrfs_read_dev_one_super(struct block_device *bdev, int copy_num,
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struct buffer_head **bh_ret)
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{
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struct buffer_head *bh;
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struct btrfs_super_block *super;
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u64 bytenr;
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bytenr = btrfs_sb_offset(copy_num);
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if (bytenr + BTRFS_SUPER_INFO_SIZE >= i_size_read(bdev->bd_inode))
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return -EINVAL;
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bh = __bread(bdev, bytenr / 4096, BTRFS_SUPER_INFO_SIZE);
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/*
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* If we fail to read from the underlying devices, as of now
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* the best option we have is to mark it EIO.
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*/
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if (!bh)
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return -EIO;
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super = (struct btrfs_super_block *)bh->b_data;
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if (btrfs_super_bytenr(super) != bytenr ||
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btrfs_super_magic(super) != BTRFS_MAGIC) {
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brelse(bh);
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return -EINVAL;
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}
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*bh_ret = bh;
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return 0;
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}
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struct buffer_head *btrfs_read_dev_super(struct block_device *bdev)
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{
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struct buffer_head *bh;
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@ -3195,7 +3226,6 @@ struct buffer_head *btrfs_read_dev_super(struct block_device *bdev)
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struct btrfs_super_block *super;
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int i;
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u64 transid = 0;
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u64 bytenr;
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int ret = -EINVAL;
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/* we would like to check all the supers, but that would make
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@ -3204,28 +3234,11 @@ struct buffer_head *btrfs_read_dev_super(struct block_device *bdev)
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* later supers, using BTRFS_SUPER_MIRROR_MAX instead
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*/
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for (i = 0; i < 1; i++) {
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bytenr = btrfs_sb_offset(i);
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if (bytenr + BTRFS_SUPER_INFO_SIZE >=
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i_size_read(bdev->bd_inode))
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break;
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bh = __bread(bdev, bytenr / 4096,
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BTRFS_SUPER_INFO_SIZE);
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/*
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* If we fail to read from the underlying devices, as of now
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* the best option we have is to mark it EIO.
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*/
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if (!bh) {
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ret = -EIO;
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ret = btrfs_read_dev_one_super(bdev, i, &bh);
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if (ret)
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continue;
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}
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super = (struct btrfs_super_block *)bh->b_data;
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if (btrfs_super_bytenr(super) != bytenr ||
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btrfs_super_magic(super) != BTRFS_MAGIC) {
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brelse(bh);
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ret = -EINVAL;
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continue;
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}
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if (!latest || btrfs_super_generation(super) > transid) {
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brelse(latest);
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@ -60,6 +60,8 @@ void close_ctree(struct btrfs_root *root);
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int write_ctree_super(struct btrfs_trans_handle *trans,
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struct btrfs_root *root, int max_mirrors);
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struct buffer_head *btrfs_read_dev_super(struct block_device *bdev);
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int btrfs_read_dev_one_super(struct block_device *bdev, int copy_num,
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struct buffer_head **bh_ret);
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int btrfs_commit_super(struct btrfs_root *root);
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struct extent_buffer *btrfs_find_tree_block(struct btrfs_fs_info *fs_info,
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u64 bytenr);
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