linux-kernel - Re: [PATCH 2/2] mm: drop PF_MEMALLOC

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Message-ID: <ZsyKQSesqc5rDFmg@casper.infradead.org>
Date: Mon, 26 Aug 2024 14:59:29 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Michal Hocko <mhocko@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Hellwig <hch@....de>, Yafang Shao <laoar.shao@...il.com>,
	Kent Overstreet <kent.overstreet@...ux.dev>, jack@...e.cz,
	Christian Brauner <brauner@...nel.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
	"Serge E. Hallyn" <serge@...lyn.com>, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org, linux-bcachefs@...r.kernel.org,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org,
	Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH 2/2] mm: drop PF_MEMALLOC_NORECLAIM

On Mon, Aug 26, 2024 at 10:47:13AM +0200, Michal Hocko wrote:
> From: Michal Hocko <mhocko@...e.com>
> 
> There is no existing user of the flag and the flag is dangerous because
> a nested allocation context can use GFP_NOFAIL which could cause
> unexpected failure. Such a code would be hard to maintain because it
> could be deeper in the call chain.
> 
> PF_MEMALLOC_NORECLAIM has been added even when it was pointed out [1]
> that such a allocation contex is inherently unsafe if the context
> doesn't fully control all allocations called from this context.

Wouldn't a straight-up revert of eab0af905bfc be cleaner?  Or is there
a reason to keep PF_MEMALLOC_NOWARN?