Re: [PATCH v3 2/2] virtiofs: use GFP_NOFS when enqueuing request through kworker

[Miklos Szeredi]

On Fri, 26 Apr 2024 at 16:38, Hou Tao <houtao@xxxxxxxxxxxxxxx> wrote:
>
> From: Hou Tao <houtao1@xxxxxxxxxx>
>
> When invoking virtio_fs_enqueue_req() through kworker, both the
> allocation of the sg array and the bounce buffer still use GFP_ATOMIC.
> Considering the size of the sg array may be greater than PAGE_SIZE, use
> GFP_NOFS instead of GFP_ATOMIC to lower the possibility of memory
> allocation failure and to avoid unnecessarily depleting the atomic
> reserves. GFP_NOFS is not passed to virtio_fs_enqueue_req() directly,
> GFP_KERNEL and memalloc_nofs_{save|restore} helpers are used instead.

Makes sense.

However, I don't understand why the GFP_NOFS behavior is optional. It
should work when queuing the request for the first time as well, no?

Thanks,
Miklos