btrfs: use own btree inode io_tree owner id

Btree inode is special compared to all other inode extent io_trees,
although it has a btrfs inode, it doesn't have the track_uptodate bit at
all.

This means a lot of things like extent locking doesn't even need to be
applied to btree io tree.

Since it's so special, adds a new owner value for it to make debuging a
little easier.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/disk-io.c

@@ -2062,7 +2062,7 @@ static void btrfs_init_btree_inode(struct btrfs_fs_info *fs_info)
 
 	RB_CLEAR_NODE(&BTRFS_I(inode)->rb_node);
 	extent_io_tree_init(fs_info, &BTRFS_I(inode)->io_tree,
-			    IO_TREE_INODE_IO, inode);
+			    IO_TREE_BTREE_INODE_IO, inode);
 	BTRFS_I(inode)->io_tree.track_uptodate = false;
 	extent_map_tree_init(&BTRFS_I(inode)->extent_tree);
 

fs/btrfs/extent-io-tree.h

@@ -40,6 +40,7 @@ struct io_failure_record;
 enum {
 	IO_TREE_FS_PINNED_EXTENTS,
 	IO_TREE_FS_EXCLUDED_EXTENTS,
+	IO_TREE_BTREE_INODE_IO,
 	IO_TREE_INODE_IO,
 	IO_TREE_INODE_IO_FAILURE,
 	IO_TREE_RELOC_BLOCKS,

include/trace/events/btrfs.h

@@ -79,6 +79,7 @@ struct btrfs_space_info;
 #define IO_TREE_OWNER						    \
 	EM( IO_TREE_FS_PINNED_EXTENTS, 	  "PINNED_EXTENTS")	    \
 	EM( IO_TREE_FS_EXCLUDED_EXTENTS,  "EXCLUDED_EXTENTS")	    \
+	EM( IO_TREE_BTREE_INODE_IO,	  "BTREE_INODE_IO")	    \
 	EM( IO_TREE_INODE_IO,		  "INODE_IO")		    \
 	EM( IO_TREE_INODE_IO_FAILURE,	  "INODE_IO_FAILURE")	    \
 	EM( IO_TREE_RELOC_BLOCKS,	  "RELOC_BLOCKS")	    \