btrfs: Rename found_type to extent_type in btrfs_get_extent

found_type really holds the type of extent and is guaranteed to to have
a value between [0, 2]. The only time it can contain anything different
is if btrfs_lookup_file_extent returned a positive value and the
previous item is different than an extent. Avoid this situation by
simply checking found_key.type rather than assigning the item type to
found_type intermittently. Also make the variable an u8 to reduce stack
usage. No functional changes.
Reviewed-by: NJohannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: NQu Wenruo <wqu@suse.com>
Signed-off-by: NNikolay Borisov <nborisov@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -6740,7 +6740,7 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
 	u64 extent_start = 0;
 	u64 extent_end = 0;
 	u64 objectid = btrfs_ino(inode);
-	u32 found_type;
+	u8 extent_type;
 	struct btrfs_path *path = NULL;
 	struct btrfs_root *root = inode->root;
 	struct btrfs_file_extent_item *item;
@@ -6806,11 +6806,9 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
 	leaf = path->nodes[0];
 	item = btrfs_item_ptr(leaf, path->slots[0],
 			      struct btrfs_file_extent_item);
-	/* are we inside the extent that was found? */
 	btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
-	found_type = found_key.type;
 	if (found_key.objectid != objectid ||
-	    found_type != BTRFS_EXTENT_DATA_KEY) {
+	    found_key.type != BTRFS_EXTENT_DATA_KEY) {
 		/*
 		 * If we backup past the first extent we want to move forward
 		 * and see if there is an extent in front of us, otherwise we'll
@@ -6821,16 +6819,16 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
 		goto next;
 	}
 
-	found_type = btrfs_file_extent_type(leaf, item);
+	extent_type = btrfs_file_extent_type(leaf, item);
 	extent_start = found_key.offset;
-	if (found_type == BTRFS_FILE_EXTENT_REG ||
-	    found_type == BTRFS_FILE_EXTENT_PREALLOC) {
+	if (extent_type == BTRFS_FILE_EXTENT_REG ||
+	    extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
 		extent_end = extent_start +
 		       btrfs_file_extent_num_bytes(leaf, item);
 
 		trace_btrfs_get_extent_show_fi_regular(inode, leaf, item,
 						       extent_start);
-	} else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
+	} else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
 		size_t size;
 
 		size = btrfs_file_extent_ram_bytes(leaf, item);
@@ -6871,10 +6869,10 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
 	btrfs_extent_item_to_extent_map(inode, path, item,
 			new_inline, em);
 
-	if (found_type == BTRFS_FILE_EXTENT_REG ||
-	    found_type == BTRFS_FILE_EXTENT_PREALLOC) {
+	if (extent_type == BTRFS_FILE_EXTENT_REG ||
+	    extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
 		goto insert;
-	} else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
+	} else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
 		unsigned long ptr;
 		char *map;
 		size_t size;