btrfs: zoned: simplify btrfs_check_meta_write_pointer

btrfs_check_meta_write_pointer() will always be called with a NULL
'cache_ret' argument.

As there's no need to check if we have a valid block_group passed in
remove these checks.
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NJohannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/zoned.c

@@ -1637,29 +1637,19 @@ bool btrfs_check_meta_write_pointer(struct btrfs_fs_info *fs_info,
 	if (!btrfs_is_zoned(fs_info))
 		return true;
 
-	cache = *cache_ret;
+	cache = btrfs_lookup_block_group(fs_info, eb->start);
+	if (!cache)
+		return true;
 
-	if (cache && (eb->start < cache->start ||
-		      cache->start + cache->length <= eb->start)) {
+	if (cache->meta_write_pointer != eb->start) {
 		btrfs_put_block_group(cache);
 		cache = NULL;
-		*cache_ret = NULL;
+		ret = false;
+	} else {
+		cache->meta_write_pointer = eb->start + eb->len;
 	}
 
-	if (!cache)
-		cache = btrfs_lookup_block_group(fs_info, eb->start);
-
-	if (cache) {
-		if (cache->meta_write_pointer != eb->start) {
-			btrfs_put_block_group(cache);
-			cache = NULL;
-			ret = false;
-		} else {
-			cache->meta_write_pointer = eb->start + eb->len;
-		}
-
-		*cache_ret = cache;
-	}
+	*cache_ret = cache;
 
 	return ret;
 }