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

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Message-ID: <ZZhkrOdbau2O/B59@casper.infradead.org>
Date: Fri, 5 Jan 2024 20:21:00 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Vivek Goyal <vgoyal@...hat.com>
Cc: Hou Tao <houtao@...weicloud.com>, 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 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?