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

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

[Naohiro Aota]

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: 568220fa9657 ("btrfs: zoned: support RAID0/1/10 on top of raid stripe tree")
CC: stable@vger.kernel.org # 6.12+
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
---
 fs/btrfs/zoned.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index 359a98e6de85..17dde95eb3e7 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -1490,6 +1490,23 @@ 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);
 
+	if (last_alloc) {
+		/*
+		 * 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;
-- 
2.52.0

Re: [PATCH] btrfs: zoned: fixup last alloc pointer after extent removal for RAID1

[Naohiro Aota]

On Wed Dec 17, 2025 at 7:34 PM JST, Naohiro Aota wrote:
> 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: 568220fa9657 ("btrfs: zoned: support RAID0/1/10 on top of raid stripe tree")
> CC: stable@vger.kernel.org # 6.12+
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
> ---
>  fs/btrfs/zoned.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
>
> diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
> index 359a98e6de85..17dde95eb3e7 100644
> --- a/fs/btrfs/zoned.c
> +++ b/fs/btrfs/zoned.c
> @@ -1490,6 +1490,23 @@ 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);
>  
> +	if (last_alloc) {

Oops, we don't need this "if" because we need to run this even if we
have no extents (alloc_offset == 0) and the write pointer > 0.

> +		/*
> +		 * 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;