btrfs: zoned: fixup last alloc pointer after extent removal for RAID1

When a block group is composed of a sequential write zone and a conventional
zone, we recover the (pseudo) write pointer of the conventional zone using the
end of the last allocated position.

However, if the last extent in a block group is removed, the last extent
position will be smaller than the other real write pointer position. Then, that
will cause an error due to mismatch of the write pointers.

We can fixup this case by moving the alloc_offset to the corresponding write
pointer position.

Fixes: 568220f ("btrfs: zoned: support RAID0/1/10 on top of raid stripe tree")
CC: [email protected] # 6.12+
Reviewed-by: Johannes Thumshirn <[email protected]>
Signed-off-by: Naohiro Aota <[email protected]>
Signed-off-by: David Sterba <[email protected]>

Author: naota

fs/btrfs/zoned.c

@@ -1491,6 +1491,21 @@ static int btrfs_load_block_group_raid1(struct btrfs_block_group *bg,
 	/* In case a device is missing we have a cap of 0, so don't use it. */
 	bg->zone_capacity = min_not_zero(zone_info[0].capacity, zone_info[1].capacity);
 
+	/*
+	 * When the last extent is removed, last_alloc can be smaller than the other write
+	 * pointer. In that case, last_alloc should be moved to the corresponding write
+	 * pointer position.
+	 */
+	for (i = 0; i < map->num_stripes; i++) {
+		if (zone_info[i].alloc_offset == WP_MISSING_DEV ||
+		    zone_info[i].alloc_offset == WP_CONVENTIONAL)
+			continue;
+		if (last_alloc <= zone_info[i].alloc_offset) {
+			last_alloc = zone_info[i].alloc_offset;
+			break;
+		}
+	}
+
 	for (i = 0; i < map->num_stripes; i++) {
 		if (zone_info[i].alloc_offset == WP_MISSING_DEV)
 			continue;