linux-kernel - Re: [PATCH 2/3] dm bufio: remove redundant __GFP

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Message-ID: <4fe735d7-736c-7bbb-173a-1bee27bbe92b@redhat.com>
Date: Mon, 11 Aug 2025 17:10:29 +0200 (CEST)
From: Mikulas Patocka <mpatocka@...hat.com>
To: Qianfeng Rong <rongqianfeng@...o.com>
cc: Alasdair Kergon <agk@...hat.com>, Mike Snitzer <snitzer@...nel.org>, 
    "open list:DEVICE-MAPPER (LVM)" <dm-devel@...ts.linux.dev>, 
    open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] dm bufio: remove redundant __GFP_NOWARN



On Mon, 11 Aug 2025, Qianfeng Rong wrote:

> 
> 在 2025/8/11 20:44, Mikulas Patocka 写道:
> > Hi
> > 
> > I think that GFP_NOWAIT already includes __GFP_NORETRY too. So, should we
> > drop __GFP_NORETRY as well?
>
> GFP_NOWAIT does not include __GFP_NORETRY:
> #define GFP_NOWAIT (__GFP_KSWAPD_RECLAIM | __GFP_NOWARN)
> 
> GFP_NOWAIT tells the memory manager to only wake up kswapd to perform
> memory reclamation, not to perform direct memory reclaim.  Even if the
> request fails, no error message is printed.
> 
> Best regards,
> Qianfeng

Yes, but if GFP_NOWAIT allocation can't sleep, it can't retry - thus 
GFP_NOWAIT should imply __GFP_NORETRY.

Mikulas