linux-kernel - RE: [PATCH v1] writback: remove WQ_MEM_RECLAIM flag in bdi

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Message-ID: <000001dbfa1a$a2a1ad80$e7e50880$@samsung.com>
Date: Mon, 21 Jul 2025 17:37:03 +0900
From: "hoyoung seo" <hy50.seo@...sung.com>
To: "'Christoph Hellwig'" <hch@...radead.org>
Cc: <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<alim.akhtar@...sung.com>, <avri.altman@....com>, <jejb@...ux.ibm.com>,
	<martin.petersen@...cle.com>, <beanhuo@...ron.com>, <bvanassche@....org>,
	<kwangwon.min@...sung.com>, <kwmad.kim@...sung.com>, <cpgs@...sung.com>,
	<h10.kim@...sung.com>, <willdeacon@...gle.com>, <jaegeuk@...gle.com>,
	<chao@...nel.org>, <linux-fsdevel@...r.kernel.org>
Subject: RE: [PATCH v1] writback: remove WQ_MEM_RECLAIM flag in bdi_wq



> -----Original Message-----
> From: Christoph Hellwig <hch@...radead.org>
> Sent: Monday, July 21, 2025 4:14 PM
> To: hy50.seo <hy50.seo@...sung.com>
> Cc: linux-scsi@...r.kernel.org; linux-kernel@...r.kernel.org;
> alim.akhtar@...sung.com; avri.altman@....com; jejb@...ux.ibm.com;
> martin.petersen@...cle.com; beanhuo@...ron.com; bvanassche@....org;
> kwangwon.min@...sung.com; kwmad.kim@...sung.com; cpgs@...sung.com;
> h10.kim@...sung.com; willdeacon@...gle.com; jaegeuk@...gle.com;
> chao@...nel.org; linux-fsdevel@...r.kernel.org
> Subject: Re: [PATCH v1] writback: remove WQ_MEM_RECLAIM flag in bdi_wq
> 
> On Mon, Jul 21, 2025 at 03:40:24PM +0900, hy50.seo wrote:
> > if it write with the write back option with f2fs, kernel panic occurs.
> > Because the write back function uses bdi_wq and WQ_MEM_RECLAIM flag is
> > included and created.
> > However, this function calls f2fs_do_quota() of f2fs and finally tries
> > to perform quota_release_work.
> > the quota_release_work is performed in the events_unbound workqueue,
> > but the WQ_MEM_RECLAIM flag is not included.
> 
> And what makes you assume the WQ_MEM_RECLAIM was added just for fun and
> can simply be deleted?

No way..
It's because i just don't know much about this part.
And WQ_MEM_RECLAIM flag is absolutely necessary.
Because it is necessary for stable write back operation when memory is
insufficient. 
is it right?
I'll find another way for fix bug.
Thanks for your reply.