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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>
This commit is contained in:
Anand Jain 2015-08-14 18:32:58 +08:00 committed by David Sterba
parent d74a625987
commit 29c36d7253
2 changed files with 35 additions and 20 deletions
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53
fs/btrfs/disk-io.c
View File

@ -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);

2
fs/btrfs/disk-io.h
View File

@ -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);