linux-kernel - Re: [PATCH v2] virtiofs: use GFP_NOFS when enqueuing request through kworker

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Date: Sat, 6 Jan 2024 10:48:37 +0800
From: Hou Tao <houtao@...weicloud.com>
To: Matthew Wilcox <willy@...radead.org>, Vivek Goyal <vgoyal@...hat.com>
Cc: linux-fsdevel@...r.kernel.org, Miklos Szeredi <miklos@...redi.hu>,
 Stefan Hajnoczi <stefanha@...hat.com>, linux-kernel@...r.kernel.org,
 virtualization@...ts.linux.dev, houtao1@...wei.com
Subject: Re: [PATCH v2] virtiofs: use GFP_NOFS when enqueuing request through
 kworker



On 1/6/2024 4:21 AM, Matthew Wilcox wrote:
> On Fri, Jan 05, 2024 at 03:17:19PM -0500, Vivek Goyal wrote:
>> On Fri, Jan 05, 2024 at 06:53:05PM +0800, Hou Tao wrote:
>>> From: Hou Tao <houtao1@...wei.com>
>>>
>>> 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 both the sg array and the bounce buffer may be
>>> greater than PAGE_SIZE, use GFP_NOFS instead of GFP_ATOMIC to lower the
>>> possibility of memory allocation failure.
>>>
>> What's the practical benefit of this patch. Looks like if memory
>> allocation fails, we keep retrying at interval of 1ms and don't
>> return error to user space.
> You don't deplete the atomic reserves unnecessarily?
Beside that, I think the proposed GFP_NOFS may reduce unnecessary
retries. I Should mention that in the commit message. Should I post a v3
to do that ?