linux-kernel - Re: [PATCH v2 1/6] workqueue: Inherit NOIO and NOFS alloc flags

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Date: Wed, 15 May 2024 06:54:11 -1000
From: Tejun Heo <tj@...nel.org>
To: Håkon Bugge <haakon.bugge@...cle.com>
Cc: linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, rds-devel@....oracle.com,
	Jason Gunthorpe <jgg@...pe.ca>, Leon Romanovsky <leon@...nel.org>,
	Saeed Mahameed <saeedm@...dia.com>,
	Tariq Toukan <tariqt@...dia.com>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Allison Henderson <allison.henderson@...cle.com>,
	Manjunath Patil <manjunath.b.patil@...cle.com>,
	Mark Zhang <markzhang@...dia.com>,
	Chuck Lever <chuck.lever@...cle.com>,
	Shiraz Saleem <shiraz.saleem@...el.com>,
	Yang Li <yang.lee@...ux.alibaba.com>
Subject: Re: [PATCH v2 1/6] workqueue: Inherit NOIO and NOFS alloc flags

> @@ -5583,6 +5600,10 @@ struct workqueue_struct *alloc_workqueue(const char *fmt,
>  
>  	/* init wq */
>  	wq->flags = flags;
> +	if (current->flags & PF_MEMALLOC_NOIO)
> +		wq->flags |= __WQ_NOIO;
> +	if (current->flags & PF_MEMALLOC_NOFS)
> +		wq->flags |= __WQ_NOFS;

So, yeah, please don't do this. What if a NOIO callers wants to scheduler a
work item so that it can user GFP_KERNEL allocations. I don't mind a
convenience feature to workqueue for this but this doesn't seem like the
right way. Also, memalloc_noio_save() and memalloc_nofs_save() are
convenience wrappers around memalloc_flags_save(), so it'd probably be
better to deal with gfp flags directly rather than singling out these two
flags.

Thanks.

-- 
tejun