btrfs-progs: check: Move lowmem check code to its own check/lowmem.[ch]

Since lowmem mode code is highly internally connected, it's pretty hard to
move them piece by piece.
In theory it's possible to move part of the functions and temporarily
export them, but it will just cause extra temporarily modifications.

So this patch moves the whole lowmem check part into its own
check/lowmem.[ch].

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Makefile

@@ -113,7 +113,7 @@ cmds_objects = cmds-subvolume.o cmds-filesystem.o cmds-device.o cmds-scrub.o \
 	       cmds-restore.o cmds-rescue.o chunk-recover.o super-recover.o \
 	       cmds-property.o cmds-fi-usage.o cmds-inspect-dump-tree.o \
 	       cmds-inspect-dump-super.o cmds-inspect-tree-stats.o cmds-fi-du.o \
-	       mkfs/common.o check/common.o
+	       mkfs/common.o check/common.o check/lowmem.o
 libbtrfs_objects = send-stream.o send-utils.o kernel-lib/rbtree.o btrfs-list.o \
 		   kernel-lib/crc32c.o messages.o \
 		   uuid-tree.o utils-lib.o rbtree-utils.o

check/lowmem.h

@@ -20,6 +20,8 @@
 #ifndef __BTRFS_CHECK_LOWMEM_H__
 #define __BTRFS_CHECK_LOWMEM_H__
 
+#include "check/common.h"
+
 #define ROOT_DIR_ERROR		(1<<1)	/* bad ROOT_DIR */
 #define DIR_ITEM_MISSING	(1<<2)	/* DIR_ITEM not found */
 #define DIR_ITEM_MISMATCH	(1<<3)	/* DIR_ITEM found but not match */
@@ -59,4 +61,7 @@
 #define ACCOUNTING_MISMATCH	(1 << 7) /* Used space accounting error */
 #define CHUNK_TYPE_MISMATCH	(1 << 8)
 
+int check_fs_roots_v2(struct btrfs_fs_info *fs_info);
+int check_chunks_and_extents_v2(struct btrfs_fs_info *fs_info);
+
 #endif