btrfs: replace BUILD_BUG_ON by static_assert

The static_assert introduced in 6bab69c6 ("build_bug.h: add wrapper
for _Static_assert") has been supported by compilers for a long time
(gcc 4.6, clang 3.0) and can be used in header files. We don't need to
put BUILD_BUG_ON to random functions but rather keep it next to the
definition.

The exception here is the UAPI header btrfs_tree.h that could be
potentially included by userspace code and the static assert is not
defined (nor used in any other header).
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/compression.h

@@ -22,6 +22,8 @@ struct btrfs_inode;
 
 /* Maximum length of compressed data stored on disk */
 #define BTRFS_MAX_COMPRESSED		(SZ_128K)
+static_assert((BTRFS_MAX_COMPRESSED % PAGE_SIZE) == 0);
+
 /* Maximum size of data before compression */
 #define BTRFS_MAX_UNCOMPRESSED		(SZ_128K)
 

fs/btrfs/ctree.h

@@ -1639,25 +1639,25 @@ DECLARE_BTRFS_SETGET_BITS(64)
 static inline u##bits btrfs_##name(const struct extent_buffer *eb,	\
 				   const type *s)			\
 {									\
-	BUILD_BUG_ON(sizeof(u##bits) != sizeof(((type *)0))->member);	\
+	static_assert(sizeof(u##bits) == sizeof(((type *)0))->member);	\
 	return btrfs_get_##bits(eb, s, offsetof(type, member));		\
 }									\
 static inline void btrfs_set_##name(const struct extent_buffer *eb, type *s, \
 				    u##bits val)			\
 {									\
-	BUILD_BUG_ON(sizeof(u##bits) != sizeof(((type *)0))->member);	\
+	static_assert(sizeof(u##bits) == sizeof(((type *)0))->member);	\
 	btrfs_set_##bits(eb, s, offsetof(type, member), val);		\
 }									\
 static inline u##bits btrfs_token_##name(struct btrfs_map_token *token,	\
 					 const type *s)			\
 {									\
-	BUILD_BUG_ON(sizeof(u##bits) != sizeof(((type *)0))->member);	\
+	static_assert(sizeof(u##bits) == sizeof(((type *)0))->member);	\
 	return btrfs_get_token_##bits(token, s, offsetof(type, member));\
 }									\
 static inline void btrfs_set_token_##name(struct btrfs_map_token *token,\
 					  type *s, u##bits val)		\
 {									\
-	BUILD_BUG_ON(sizeof(u##bits) != sizeof(((type *)0))->member);	\
+	static_assert(sizeof(u##bits) == sizeof(((type *)0))->member);	\
 	btrfs_set_token_##bits(token, s, offsetof(type, member), val);	\
 }
 
@@ -1688,7 +1688,7 @@ static inline void btrfs_set_##name(type *s, u##bits val)		\
 static inline u64 btrfs_device_total_bytes(const struct extent_buffer *eb,
 					   struct btrfs_dev_item *s)
 {
-	BUILD_BUG_ON(sizeof(u64) !=
+	static_assert(sizeof(u64) ==
 		      sizeof(((struct btrfs_dev_item *)0))->total_bytes);
 	return btrfs_get_64(eb, s, offsetof(struct btrfs_dev_item,
 					    total_bytes));
@@ -1697,7 +1697,7 @@ static inline void btrfs_set_device_total_bytes(const struct extent_buffer *eb,
 						struct btrfs_dev_item *s,
 						u64 val)
 {
-	BUILD_BUG_ON(sizeof(u64) !=
+	static_assert(sizeof(u64) ==
 		      sizeof(((struct btrfs_dev_item *)0))->total_bytes);
 	WARN_ON(!IS_ALIGNED(val, eb->fs_info->sectorsize));
 	btrfs_set_64(eb, s, offsetof(struct btrfs_dev_item, total_bytes), val);

fs/btrfs/inode.c

@@ -629,7 +629,6 @@ static noinline int compress_file_range(struct async_chunk *async_chunk)
 again:
 	will_compress = 0;
 	nr_pages = (end >> PAGE_SHIFT) - (start >> PAGE_SHIFT) + 1;
-	BUILD_BUG_ON((BTRFS_MAX_COMPRESSED % PAGE_SIZE) != 0);
 	nr_pages = min_t(unsigned long, nr_pages,
 			BTRFS_MAX_COMPRESSED / PAGE_SIZE);
 
@@ -5609,21 +5608,17 @@ static struct inode *new_simple_dir(struct super_block *s,
 	return inode;
 }
 
+static_assert(BTRFS_FT_UNKNOWN == FT_UNKNOWN);
+static_assert(BTRFS_FT_REG_FILE == FT_REG_FILE);
+static_assert(BTRFS_FT_DIR == FT_DIR);
+static_assert(BTRFS_FT_CHRDEV == FT_CHRDEV);
+static_assert(BTRFS_FT_BLKDEV == FT_BLKDEV);
+static_assert(BTRFS_FT_FIFO == FT_FIFO);
+static_assert(BTRFS_FT_SOCK == FT_SOCK);
+static_assert(BTRFS_FT_SYMLINK == FT_SYMLINK);
+
 static inline u8 btrfs_inode_type(struct inode *inode)
 {
-	/*
-	 * Compile-time asserts that generic FT_* types still match
-	 * BTRFS_FT_* types
-	 */
-	BUILD_BUG_ON(BTRFS_FT_UNKNOWN != FT_UNKNOWN);
-	BUILD_BUG_ON(BTRFS_FT_REG_FILE != FT_REG_FILE);
-	BUILD_BUG_ON(BTRFS_FT_DIR != FT_DIR);
-	BUILD_BUG_ON(BTRFS_FT_CHRDEV != FT_CHRDEV);
-	BUILD_BUG_ON(BTRFS_FT_BLKDEV != FT_BLKDEV);
-	BUILD_BUG_ON(BTRFS_FT_FIFO != FT_FIFO);
-	BUILD_BUG_ON(BTRFS_FT_SOCK != FT_SOCK);
-	BUILD_BUG_ON(BTRFS_FT_SYMLINK != FT_SYMLINK);
-
 	return fs_umode_to_ftype(inode->i_mode);
 }
 

fs/btrfs/ioctl.c

@@ -1527,6 +1527,7 @@ static int defrag_collect_targets(struct btrfs_inode *inode,
 }
 
 #define CLUSTER_SIZE	(SZ_256K)
+static_assert(IS_ALIGNED(CLUSTER_SIZE, PAGE_SIZE));
 
 /*
  * Defrag one contiguous target range.
@@ -1672,7 +1673,6 @@ static int defrag_one_cluster(struct btrfs_inode *inode,
 	LIST_HEAD(target_list);
 	int ret;
 
-	BUILD_BUG_ON(!IS_ALIGNED(CLUSTER_SIZE, PAGE_SIZE));
 	ret = defrag_collect_targets(inode, start, len, extent_thresh,
 				     newer_than, do_compress, false,
 				     &target_list, NULL);
@@ -1815,9 +1815,6 @@ int btrfs_defrag_file(struct inode *inode, struct file_ra_state *ra,
 		u64 last_scanned = cur;
 		u64 cluster_end;
 
-		/* The cluster size 256K should always be page aligned */
-		BUILD_BUG_ON(!IS_ALIGNED(CLUSTER_SIZE, PAGE_SIZE));
-
 		if (btrfs_defrag_cancelled(fs_info)) {
 			ret = -EAGAIN;
 			break;

fs/btrfs/sysfs.c

@@ -1107,6 +1107,11 @@ static inline struct btrfs_fs_info *to_fs_info(struct kobject *kobj)
 static char btrfs_unknown_feature_names[FEAT_MAX][NUM_FEATURE_BITS][BTRFS_FEATURE_NAME_MAX];
 static struct btrfs_feature_attr btrfs_feature_attrs[FEAT_MAX][NUM_FEATURE_BITS];
 
+static_assert(ARRAY_SIZE(btrfs_unknown_feature_names) ==
+	      ARRAY_SIZE(btrfs_feature_attrs));
+static_assert(ARRAY_SIZE(btrfs_unknown_feature_names[0]) ==
+	      ARRAY_SIZE(btrfs_feature_attrs[0]));
+
 static const u64 supported_feature_masks[FEAT_MAX] = {
 	[FEAT_COMPAT]    = BTRFS_FEATURE_COMPAT_SUPP,
 	[FEAT_COMPAT_RO] = BTRFS_FEATURE_COMPAT_RO_SUPP,
@@ -1275,11 +1280,6 @@ static void init_feature_attrs(void)
 	struct btrfs_feature_attr *fa;
 	int set, i;
 
-	BUILD_BUG_ON(ARRAY_SIZE(btrfs_unknown_feature_names) !=
-		     ARRAY_SIZE(btrfs_feature_attrs));
-	BUILD_BUG_ON(ARRAY_SIZE(btrfs_unknown_feature_names[0]) !=
-		     ARRAY_SIZE(btrfs_feature_attrs[0]));
-
 	memset(btrfs_feature_attrs, 0, sizeof(btrfs_feature_attrs));
 	memset(btrfs_unknown_feature_names, 0,
 	       sizeof(btrfs_unknown_feature_names));