fs: btrfs: Crossport btrfs_read_dev_super() from btrfs-progs

This patch uses generic code from btrfs-progs to read one super block
from block device.

To support the btrfs-progs coding style, the following is also
crossported:
- BTRFS_SETGET_FUNC for btrfs_super_block
- btrfs_check_super() function
- Move btrfs_read_superblock() to disk-io.[ch]
  Since super.c only contains pretty small amount of code, and
  the extra check will be covered in later root read patches.

Differences between this implementation and btrfs-progs:
- No sbflags/sb_bytenr support
  Since we only need to read the primary super block (like kernel),
  sbflags/sb_bytenr used by super block recovery is not needed.

This also changes the following behavior of U-Boot btrfs:
- Only reads the primary super block
  The old implementation reads all 3 super blocks, and also one
  non-existing backup.
  This is not correct, especially if there is another filesystem created
  on the device but old superblocks are not rewritten.

  Just like kernel, we only check the primary super block.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Marek Behún <marek.behun@nic.cz>
[trini: Change error to be a define in compat.h]
Signed-off-by: Tom Rini <trini@konsulko.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index efb7158..fe4093c 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -2,10 +2,14 @@
 #ifndef __BTRFS_DISK_IO_H__
 #define __BTRFS_DISK_IO_H__
 
+#include <linux/sizes.h>
+#include <fs_internal.h>
 #include "crypto/hash.h"
 #include "ctree.h"
 #include "disk-io.h"
 
+#define BTRFS_SUPER_INFO_OFFSET SZ_64K
+#define BTRFS_SUPER_INFO_SIZE	SZ_4K
 static inline u64 btrfs_name_hash(const char *name, int len)
 {
 	u32 crc;
@@ -17,4 +21,7 @@ static inline u64 btrfs_name_hash(const char *name, int len)
 
 int btrfs_csum_data(u16 csum_type, const u8 *data, u8 *out, size_t len);
 
+int btrfs_read_dev_super(struct blk_desc *desc, struct disk_partition *part,
+			 struct btrfs_super_block *sb);
+int btrfs_read_superblock(void);
 #endif