btrfs: add helpers for compression type and level

It is very easy to miss places that rely on a certain bitshifting for
decoding the type_level overloading. Add helpers to do this instead.

Cc: Omar Sandoval <osandov@osandov.com>
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NDennis Zhou <dennis@kernel.org>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/compression.c

@@ -1036,9 +1036,9 @@ int btrfs_compress_pages(unsigned int type_level, struct address_space *mapping,
 			 unsigned long *total_in,
 			 unsigned long *total_out)
 {
+	int type = btrfs_compress_type(type_level);
 	struct list_head *workspace;
 	int ret;
-	int type = type_level & 0xF;
 
 	workspace = find_workspace(type);
 

fs/btrfs/compression.h

@@ -64,6 +64,16 @@ struct compressed_bio {
 	u32 sums;
 };
 
+static inline unsigned int btrfs_compress_type(unsigned int type_level)
+{
+	return (type_level & 0xF);
+}
+
+static inline unsigned int btrfs_compress_level(unsigned int type_level)
+{
+	return ((type_level & 0xF0) >> 4);
+}
+
 void __init btrfs_init_compress(void);
 void __cold btrfs_exit_compress(void);
 

fs/btrfs/zlib.c

@@ -393,7 +393,7 @@ static int zlib_decompress(struct list_head *ws, unsigned char *data_in,
 static void zlib_set_level(struct list_head *ws, unsigned int type)
 {
 	struct workspace *workspace = list_entry(ws, struct workspace, list);
-	unsigned level = (type & 0xF0) >> 4;
+	unsigned int level = btrfs_compress_level(type);
 
 	if (level > 9)
 		level = 9;