fs: btrfs: Implement btrfs_file_read()

This version of btrfs_file_read() has the following new features:
- Tries all mirrors
- More handling on unaligned size
- Better compressed extent handling
  The old implementation doesn't handle compressed extent with offset
  properly: we need to read out the whole compressed extent, then
  decompress the whole extent, and only then copy the requested part.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Marek Behún <marek.behun@nic.cz>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/btrfs/btrfs.h b/fs/btrfs/btrfs.h
index 32ea2fc53aa..268ca077d96 100644
--- a/fs/btrfs/btrfs.h
+++ b/fs/btrfs/btrfs.h
@@ -59,6 +59,8 @@ int btrfs_readlink(struct btrfs_root *root, u64 ino, char *target);
 u64 __btrfs_lookup_path(struct __btrfs_root *, u64, const char *, u8 *,
 		       struct btrfs_inode_item *, int);
 u64 __btrfs_file_read(const struct __btrfs_root *, u64, u64, u64, char *);
+int btrfs_file_read(struct btrfs_root *root, u64 ino, u64 file_offset, u64 len,
+		    char *dest);
 
 /* subvolume.c */
 u64 btrfs_get_default_subvol_objectid(void);