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

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Date: Mon, 08 Jan 2024 10:48:24 -0500
From: Benjamin Coddington <bcodding@...hat.com>
To: Hou Tao <houtao@...weicloud.com>
Cc: linux-fsdevel@...r.kernel.org, Miklos Szeredi <miklos@...redi.hu>,
 Vivek Goyal <vgoyal@...hat.com>, Stefan Hajnoczi <stefanha@...hat.com>,
 Matthew Wilcox <willy@...radead.org>, 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 5 Jan 2024, at 5:53, 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.

Perhaps not appropriate for this case, but are you aware of
memalloc_nofs_save/restore?  NFS has been converting over and cleaning out
our GFP_NOFS usage:

Documentation/core-api/gfp_mask-from-fs-io.rst

Ben