[PATCH 2/2] btrfs: zoned: skip reporting zone for new block group

Naohiro Aota
2025-03-12T01:32:22Z

There is a potential deadlock if we do report zones in an IO context. When one
process do a report zones and another process freezes the block device, the
report zones side cannot allocate a tag because the freeze is already started.
This can thus result in new block group creation to hang forever, blocking the
write path.

Thankfully, a new block group should be created on empty zones. So, reporting
the zones is not necessary and we can set the write pointer = 0 and load the
zone capacity from the block layer using bdev_zone_capacity() helper.

CC: stable@vger.kernel.org # 6.13+
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
---
fs/btrfs/zoned.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index 4956baf8220a..6c730f6bce10 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -1277,7 +1277,7 @@ struct zone_info {

static int btrfs_load_zone_info(struct btrfs_fs_info *fs_info, int zone_idx,
struct zone_info *info, unsigned long *active,
- struct btrfs_chunk_map *map)
+ struct btrfs_chunk_map *map, bool new)
{
struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
struct btrfs_device *device;
@@ -1307,6 +1307,8 @@ static int btrfs_load_zone_info(struct btrfs_fs_info *fs_info, int zone_idx,
return 0;
}

+ ASSERT(!new || btrfs_dev_is_empty_zone(device, info->physical));
+
/* This zone will be used for allocation, so mark this zone non-empty. */
btrfs_dev_clear_zone_empty(device, info->physical);

@@ -1319,6 +1321,18 @@ static int btrfs_load_zone_info(struct btrfs_fs_info *fs_info, int zone_idx,
* to determine the allocation offset within the zone.
*/
WARN_ON(!IS_ALIGNED(info->physical, fs_info->zone_size));
+
+ if (new) {
+ sector_t capacity;
+
+ capacity = bdev_zone_capacity(device->bdev, info->physical >> SECTOR_SHIFT);
+ up_read(&dev_replace->rwsem);
+ info->alloc_offset = 0;
+ info->capacity = capacity << SECTOR_SHIFT;
+
+ return 0;
+ }
+
nofs_flag = memalloc_nofs_save();
ret = btrfs_get_dev_zone(device, info->physical, &zone);
memalloc_nofs_restore(nofs_flag);
@@ -1588,7 +1602,7 @@ int btrfs_load_block_group_zone_info(struct btrfs_block_group *cache, bool new)
}

for (i = 0; i < map->num_stripes; i++) {
- ret = btrfs_load_zone_info(fs_info, i, &zone_info[i], active, map);
+ ret = btrfs_load_zone_info(fs_info, i, &zone_info[i], active, map, new);
if (ret)
goto out;

--
2.48.1