Re: [PATCH v2 1/3] btrfs: avoid double clean up when submit_one_bio() failed

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 2022/4/15 14:28, Christoph Hellwig wrote:
> Btw, btrfs_submit_compressed_write also seems to do some double cleanups,
> even if the pattern is slightly different as the bio is allocated inside
> btrfs_submit_compressed_write itself.  Can someone who is more familiar
> with that code look into that?

I just checked the code, it's indeed causing problems.

If btrfs_csum_one_bio() or submit_compressed_bio() failed (either ENOMEM
or failed some sanity checks), then we have one bio for writing the
compressed data back to disk.

Finish_cb label will call endio on it, which will call:
  -> end_compressed_bio_write()
     -> finish_compressed_bio() (this needs the compressed write bio not
be split)

Then finish_cb tag will also call finish_compressed_bio() directly.
Double freeing cb, and double clearing writeback flags.

The only relief is, regular EIO won't trigger the bug for write path.


But this can not be said to btrfs_submit_compressed_read(), which has
the same problem and can be triggered by EIO error easily.

Do you want to give it a try? Or mind to me fix it?

Thanks,
Qu