From: Johannes Thumshirn Date: Fri, 3 Jul 2026 05:54:45 +0000 (+0200) Subject: btrfs: zoned: reset meta_write_pointer on zone reset X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5fabb1cf25d723274009d7b759545fd59f230c9d;p=thirdparty%2Flinux.git btrfs: zoned: reset meta_write_pointer on zone reset btrfs_reset_unused_block_groups() resets a block group's zone and sets alloc_offset back to 0 so the space can be reused, but it leaves meta_write_pointer pointing at the previous end of the zone. Once the block group is reactivated and reused for metadata, newly allocated tree blocks live before that stale write pointer. btrfs_check_meta_write_pointer() then sees them behind the write pointer, so they can never be written out in sequential order: the dirty extent buffers are stranded and pin their btree_inode folios until unmount. Reset meta_write_pointer back to the start of the block group for metadata and system block groups. Fixes: 453a73c3069a ("btrfs: zoned: reclaim unused zone by zone resetting") Reviewed-by: Naohiro Aota Signed-off-by: Johannes Thumshirn Signed-off-by: David Sterba --- diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c index 44a13ed6b8b2..0706c0788cb2 100644 --- a/fs/btrfs/zoned.c +++ b/fs/btrfs/zoned.c @@ -3189,6 +3189,17 @@ int btrfs_reset_unused_block_groups(struct btrfs_space_info *space_info, u64 num reclaimed = bg->alloc_offset; bg->zone_unusable = bg->length - bg->zone_capacity; bg->alloc_offset = 0; + /* + * The zone was just reset to empty, so alloc_offset went back to + * the start of the zone. For metadata/system block groups the + * write pointer must follow it back to the start of the zone; + * otherwise it stays stale at the previous (finished) zone end, + * and metadata written into the reused zone would sit behind the + * write pointer, could never be written out in sequential order, + * and would be stranded (pinning its folio) until unmount. + */ + if (bg->flags & (BTRFS_BLOCK_GROUP_METADATA | BTRFS_BLOCK_GROUP_SYSTEM)) + bg->meta_write_pointer = bg->start; /* * This holds because we currently reset fully used then freed * block group.