btrfs: rename macro local variables that clash with other variables

Fix variable names in two macros where there's a local function variable
of the same name.  In subpage_calc_start_bit() it's in several callers,
in btrfs_abort_transaction() it's only in replace_file_extents().
Found by 'make W=2'.
Reviewed-by: Boris Burkov <boris@bur.io>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/subpage.c

@@ -242,12 +242,12 @@ static void btrfs_subpage_assert(const struct btrfs_fs_info *fs_info,
 
 #define subpage_calc_start_bit(fs_info, folio, name, start, len)	\
 ({									\
-	unsigned int start_bit;						\
+	unsigned int __start_bit;						\
 									\
 	btrfs_subpage_assert(fs_info, folio, start, len);		\
-	start_bit = offset_in_page(start) >> fs_info->sectorsize_bits;	\
-	start_bit += fs_info->subpage_info->name##_offset;		\
-	start_bit;							\
+	__start_bit = offset_in_page(start) >> fs_info->sectorsize_bits; \
+	__start_bit += fs_info->subpage_info->name##_offset;		\
+	__start_bit;							\
 })
 
 void btrfs_subpage_start_reader(const struct btrfs_fs_info *fs_info,

fs/btrfs/transaction.h

@@ -229,11 +229,11 @@ bool __cold abort_should_print_stack(int error);
  */
 #define btrfs_abort_transaction(trans, error)		\
 do {								\
-	bool first = false;					\
+	bool __first = false;					\
 	/* Report first abort since mount */			\
 	if (!test_and_set_bit(BTRFS_FS_STATE_TRANS_ABORTED,	\
 			&((trans)->fs_info->fs_state))) {	\
-		first = true;					\
+		__first = true;					\
 		if (WARN(abort_should_print_stack(error),	\
 			KERN_ERR				\
 			"BTRFS: Transaction aborted (error %d)\n",	\
@@ -246,7 +246,7 @@ do {								\
 		}						\
 	}							\
 	__btrfs_abort_transaction((trans), __func__,		\
-				  __LINE__, (error), first);	\
+				  __LINE__, (error), __first);	\
 } while (0)
 
 int btrfs_end_transaction(struct btrfs_trans_handle *trans);