On 2021/11/29 19:21, Christoph Hellwig wrote:

On Sun, Nov 28, 2021 at 04:42:35PM +0900, Tetsuo Handa wrote:

quoted

Is dropping disk->open_mutex inside lo_release()
( https://lkml.kernel.org/r/e4bdc6b1-701d-6cc1-5d42-65564d2aa089@I-love.SAKURA.ne.jp ) possible?

I don't think we can drop open_mutex inside ->release. What is the
problem with offloading the clearing to a different context than the
one that calls ->release?

Offloading to a WQ context?

If the caller just want to call ioctl(LOOP_CTL_GET_FREE) followed by
ioctl(LOOP_CONFIGURE), deferring __loop_clr_fd() would be fine.

But the caller might want to unmount as soon as fput(filp) from __loop_clr_fd() completes.
I think we need to wait for __loop_clr_fd() from lo_release() to complete.