Re: [PATCH] dm-crypt: defer async write submission to write thread

[Mikulas Patocka <mpatocka@redhat.com>]

On Mon, 9 Nov 2026, Damien Le Moal wrote:

> On 11/5/26 16:27, Josef Schlehofer wrote:
> > With no_write_workqueue, kcryptd_crypt_write_io_submit() submits the
> > bio directly, even when called from kcryptd_async_done(). An async
> > cipher may run this callback in softirq or with BH disabled, where
> > submit_bio_noacct() must not be called because it can sleep.
> > 
> > Submit inline only when async is false. Async completions are sent to
> > the write thread, as is already done for submit_from_crypt_cpus. Use
> > the async flag rather than in_interrupt(), since callback context
> > depends on the cipher driver. Sync ciphers still submit inline.
> > 
> > Tested with cryptd in QEMU (x86_64 and arm64) with
> > CONFIG_DEBUG_ATOMIC_SLEEP, and on a P2020 running 6.18.55 without it.
> 
> Originally, this was added to avoid write reordering for zoned block devices.
> So did you test this change with that (scsi_debug or null-blk) ? You can also
> use an emulated NVMe ZNS device in QEMU.

So, should we disable asynchronous crypto operations for zoned devices? 
Would you send a patch for that?

Mikulas