btrfs: simplify variables in btrfs_block_rsv_refill()

At btrfs_block_rsv_refill(), there's no point in initializing the
'num_bytes' variable to 0 and then, after taking the block reserve's
spinlock, initializing it to the value of the 'min_reserved' parameter.

So just get rid of the 'num_bytes' local variable and rename the
'min_reserved' parameter to 'num_bytes'.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/block-rsv.c

@@ -242,17 +242,15 @@ int btrfs_block_rsv_check(struct btrfs_block_rsv *block_rsv, int min_percent)
 }
 
 int btrfs_block_rsv_refill(struct btrfs_fs_info *fs_info,
-			   struct btrfs_block_rsv *block_rsv, u64 min_reserved,
+			   struct btrfs_block_rsv *block_rsv, u64 num_bytes,
 			   enum btrfs_reserve_flush_enum flush)
 {
-	u64 num_bytes = 0;
 	int ret = -ENOSPC;
 
 	if (!block_rsv)
 		return 0;
 
 	spin_lock(&block_rsv->lock);
-	num_bytes = min_reserved;
 	if (block_rsv->reserved >= num_bytes)
 		ret = 0;
 	else

fs/btrfs/block-rsv.h

@@ -65,7 +65,7 @@ int btrfs_block_rsv_add(struct btrfs_fs_info *fs_info,
 			enum btrfs_reserve_flush_enum flush);
 int btrfs_block_rsv_check(struct btrfs_block_rsv *block_rsv, int min_percent);
 int btrfs_block_rsv_refill(struct btrfs_fs_info *fs_info,
-			   struct btrfs_block_rsv *block_rsv, u64 min_reserved,
+			   struct btrfs_block_rsv *block_rsv, u64 num_bytes,
 			   enum btrfs_reserve_flush_enum flush);
 int btrfs_block_rsv_migrate(struct btrfs_block_rsv *src_rsv,
 			    struct btrfs_block_rsv *dst_rsv, u64 num_bytes,