[PATCH 13/26] btrfs-progs: zoned: implement sequential extent allocation

[Naohiro Aota <naohiro.aota@wdc.com>]

Implement a sequential extent allocator for zoned filesystems. This
allocator only needs to check if there is enough space in the block group
after the allocation pointer to satisfy the extent allocation request.

Since the allocator is really simple, we implement it directly in
find_search_start().

Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
---
 kernel-shared/extent-tree.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel-shared/extent-tree.c b/kernel-shared/extent-tree.c
index ec5ea9a8e090..7453bf9f49b6 100644
--- a/kernel-shared/extent-tree.c
+++ b/kernel-shared/extent-tree.c
@@ -284,6 +284,14 @@ again:
 	if (cache->ro || !block_group_bits(cache, data))
 		goto new_group;
 
+	if (btrfs_is_zoned(root->fs_info)) {
+		if (cache->length - cache->alloc_offset < num)
+			goto new_group;
+		*start_ret = cache->start + cache->alloc_offset;
+		cache->alloc_offset += num;
+		return 0;
+	}
+
 	while(1) {
 		ret = find_first_extent_bit(&root->fs_info->free_space_cache,
 					    last, &start, &end, EXTENT_DIRTY);
-- 
2.31.1