linux-kernel - Re: [PATCH 1/1] mm: bdi: Initialize bdi_min

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Date:   Fri, 22 Oct 2021 03:58:13 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Manjong Lee <mj0123.lee@...sung.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, seunghwan.hyun@...sung.com,
        sookwan7.kim@...sung.com, nanich.lee@...sung.com,
        yt0928.kim@...sung.com, junho89.kim@...sung.com,
        jisoo2146.oh@...sung.com
Subject: Re: [PATCH 1/1] mm: bdi: Initialize bdi_min_ratio when bdi unregister

On Thu, Oct 21, 2021 at 07:45:30PM -0700, Andrew Morton wrote:
> On Thu, 21 Oct 2021 13:01:30 +0100 Matthew Wilcox <willy@...radead.org> wrote:
> 
> > On Thu, Oct 21, 2021 at 04:16:52AM -0700, Christoph Hellwig wrote:
> > > On Fri, Oct 22, 2021 at 01:19:43AM +0900, Manjong Lee wrote:
> > > > Because when sdcard is removed, bdi_min_ratio value will remain.
> > > > Currently, the only way to reset bdi_ min_ratio is to reboot.
> > > 
> > > But bdis that are unregistered are never re-registered.  What is
> > > the problem you're trying to solve?
> > 
> > The global bdi_min_ratio needs to be adjusted.  See
> > bdi_set_min_ratio() in mm/page-writeback.c.
> 
> I added cc:stable to this and tweaked the comment & coding style a bit:

Definitely improvements on that front.

I don't know the BDI code particularly well, and the implementation of
bdi_set_min_ratio() confuses me, so I can't say whether the original
patch is clearly correct or not.