Re: [PATCH 2/5] btrfs: zoned: drop stale dirty btree buffers at close_ctree()

On 17.07.26 00:49, Qu Wenruo wrote:
> 
> 
> 在 2026/7/16 21:26, Johannes Thumshirn 写道:
>> On a zoned filesystem btrfs_clear_buffer_dirty() keeps a freed-but-dirty
>> tree block dirty (EXTENT_BUFFER_ZONED_ZEROOUT) so its zero-out keeps the
>> zone write pointer moving. A block left ahead of the block group's
>> meta_write_pointer (e.g. a tree-log block freed before being written) can
>> never be written by btree_writepages() and survives to unmount.
>>
>> close_ctree() stops the endio workqueues before the final iput() of the
>> btree inode but frees the block groups only afterwards. Once the block
>> group is gone btrfs_check_meta_write_pointer() no longer defers the 
>> buffer,
>> so the iput() submits it for writeback; its completion can no longer be
>> queued on the destroyed endio_meta_workers and umount hangs on writeback
>> that never finishes.
> 
> Can we just trigger a btree inode write back for zoned cases?
> 
> That sounds much simpler and less hacky.
I tried freeing the stale ebs in btrfs_reset_unused_block_groups() 
before actually resetting the bg, but then the WARN() in 
invalidate_and_check_btree_folios() triggered again. So that doesn't 
work sorry.