linux-kernel - Re: [PATCH] maple_tree: use GFP_KERNEL on mas_node

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Message-ID: <ZPlNPGpAPy+7oQay@casper.infradead.org>
Date:   Thu, 7 Sep 2023 05:10:36 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Peng Zhang <zhangpeng.00@...edance.com>
Cc:     심재선 <jason.sim@...sung.com>,
        "liam.howlett@...cle.com" <liam.howlett@...cle.com>,
        "surenb@...gle.com" <surenb@...gle.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jaewon31.kim@...il.com" <jaewon31.kim@...il.com>,
        "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>
Subject: Re: [PATCH] maple_tree: use GFP_KERNEL on mas_node_count

On Thu, Sep 07, 2023 at 12:02:02PM +0800, Peng Zhang wrote:
> 
> 
> 在 2023/9/7 11:49, Matthew Wilcox 写道:
> > On Thu, Sep 07, 2023 at 12:39:14PM +0900, 심재선 wrote:
> > > Use GFP_KERNEL on mas_node_count instead of GFP_NOWAIT | __GFP_NOWARN
> > > in order to allow memory reclaim.
> There are many paths that call maple tree's mas_node_count(). Some paths
> cannot reclaim memory.

Right ... but we should be handling the ENOMEM inside the maple tree and
allocating some nodes with GFP_KERNEL instead of failing fork().

> > What testing did you do of this patch?  In particular, did you try it
> > with lockdep enabled?