From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id B20CEC5321D for ; Mon, 26 Aug 2024 19:20:16 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3F9E96B007B; Mon, 26 Aug 2024 15:20:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3AA2C6B0082; Mon, 26 Aug 2024 15:20:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 271F96B0088; Mon, 26 Aug 2024 15:20:16 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 07B966B007B for ; Mon, 26 Aug 2024 15:20:16 -0400 (EDT) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 7B94F81497 for ; Mon, 26 Aug 2024 19:20:15 +0000 (UTC) X-FDA: 82495362390.20.D2308D7 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf14.hostedemail.com (Postfix) with ESMTP id 247FB100011 for ; Mon, 26 Aug 2024 19:20:12 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=JWEURzJp; spf=none (imf14.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1724699946; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=yjKrCodld8mbOV/lM4+5WUcrI6600Kgbv5GVWkH6l9I=; b=VNYDQecyNyoOqVDgjqgDl1k5/bFFDN4+vZlq7UqNJctukHOzGR5W3AofTgeBnzzD1NRYSy hZ7Bawep951UAC3juvjnk/kIz+HGiyOQ0dynfZaZKOE9dS6Y8yuTarcTtJNOM7x4n2cvmN kGNg/U4s9ukYRvMZTLS/D4flbKxJHVM= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=JWEURzJp; spf=none (imf14.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1724699946; a=rsa-sha256; cv=none; b=Mlg0VXfEPsQWUo1wJ1aZZqRyzly7iZFBk+ciCqGde2n9dHFrZDwo2WzR11CpOvmY4SWPxa UerrPuWRoXiMiijNHiiWoivtHMiB3AUv55kygaEK9yOIhzgZqM1HG/DCRXvQ8+Z7+zmAO8 iFklZuPGLr2dcB0xnVzHC3FioJQ3hgo= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=yjKrCodld8mbOV/lM4+5WUcrI6600Kgbv5GVWkH6l9I=; b=JWEURzJp5Uaqr7feHKFvhix5DO pW2WNEtWNsMJK99Z25yikjA4azTuEY5eCa8HC6WdG577dPxsJsjWZTureRmNt/frzwJCPccjNvzQQ 2aCfU4WkOP+drKkSEcOs8jul4tJq9iW1JypZBytn9GYCGtvoCjo92SIlL83t0QsVCLoNexbqLphuv 2WuufdPHfhbITSDR/dCS1n3fH6pjp2f4E4LRlKbUUqPqfXOcXJx6QS+ISMKYbkECoZaEHVtftYpfI b2kw7EQVKWJX+Y2q6+TqJNFamTZIfrAA8WfUCVRcaLN0LEDQhsbL9kZbPrZWjXr9SFY9lmMeHDSll VR19Q7Jw==; Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1sifFz-0000000FujW-1zIQ; Mon, 26 Aug 2024 19:20:03 +0000 Date: Mon, 26 Aug 2024 20:20:03 +0100 From: Matthew Wilcox To: Michal Hocko Cc: Andrew Morton , Christoph Hellwig , Yafang Shao , Kent Overstreet , jack@suse.cz, Christian Brauner , Alexander Viro , Paul Moore , James Morris , "Serge E. Hallyn" , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-bcachefs@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] mm: drop PF_MEMALLOC_NORECLAIM Message-ID: References: <20240826085347.1152675-1-mhocko@kernel.org> <20240826085347.1152675-3-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: gcc4k6se5br6fdczpaoeucksjj1qws9g X-Rspam-User: X-Rspamd-Queue-Id: 247FB100011 X-Rspamd-Server: rspam02 X-HE-Tag: 1724700012-430767 X-HE-Meta: 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 o6ORwcYS 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Aug 26, 2024 at 09:18:01PM +0200, Michal Hocko wrote: > On Mon 26-08-24 18:49:23, Matthew Wilcox wrote: > > On Mon, Aug 26, 2024 at 06:51:55PM +0200, Michal Hocko wrote: > [...] > > > If a plan revert is preferably, I will go with it. > > > > There aren't any other users of PF_MEMALLOC_NOWARN and it definitely > > seems like something you want at a callsite rather than blanket for every > > allocation below this point. We don't seem to have many PF_ flags left, > > so let's not keep it around if there's no immediate plans for it. > > Good point. What about this? Looks clean to me. Reviewed-by: Matthew Wilcox (Oracle) > >From 923cd429d4b1a3520c93bcf46611ae74a3158865 Mon Sep 17 00:00:00 2001 > From: Michal Hocko > Date: Mon, 26 Aug 2024 21:15:02 +0200 > Subject: [PATCH] Revert "mm: introduce PF_MEMALLOC_NORECLAIM, > PF_MEMALLOC_NOWARN" > > This reverts commit eab0af905bfc3e9c05da2ca163d76a1513159aa4. > > There is no existing user of those flags. PF_MEMALLOC_NOWARN 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. > > While PF_MEMALLOC_NOWARN is not dangerous the way PF_MEMALLOC_NORECLAIM > is it doesn't have any user and as Matthew has pointed out we are > running out of those flags so better reclaim it without any real users. > > [1] https://lore.kernel.org/all/ZcM0xtlKbAOFjv5n@tiehlicka/ > > Signed-off-by: Michal Hocko > --- > include/linux/sched.h | 4 ++-- > include/linux/sched/mm.h | 17 ++++------------- > 2 files changed, 6 insertions(+), 15 deletions(-) > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index f8d150343d42..731ff1078c9e 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -1657,8 +1657,8 @@ extern struct pid *cad_pid; > * I am cleaning dirty pages from some other bdi. */ > #define PF_KTHREAD 0x00200000 /* I am a kernel thread */ > #define PF_RANDOMIZE 0x00400000 /* Randomize virtual address space */ > -#define PF_MEMALLOC_NORECLAIM 0x00800000 /* All allocation requests will clear __GFP_DIRECT_RECLAIM */ > -#define PF_MEMALLOC_NOWARN 0x01000000 /* All allocation requests will inherit __GFP_NOWARN */ > +#define PF__HOLE__00800000 0x00800000 > +#define PF__HOLE__01000000 0x01000000 > #define PF__HOLE__02000000 0x02000000 > #define PF_NO_SETAFFINITY 0x04000000 /* Userland is not allowed to meddle with cpus_mask */ > #define PF_MCE_EARLY 0x08000000 /* Early kill for mce process policy */ > diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h > index 91546493c43d..07c4fde32827 100644 > --- a/include/linux/sched/mm.h > +++ b/include/linux/sched/mm.h > @@ -258,25 +258,16 @@ static inline gfp_t current_gfp_context(gfp_t flags) > { > unsigned int pflags = READ_ONCE(current->flags); > > - if (unlikely(pflags & (PF_MEMALLOC_NOIO | > - PF_MEMALLOC_NOFS | > - PF_MEMALLOC_NORECLAIM | > - PF_MEMALLOC_NOWARN | > - PF_MEMALLOC_PIN))) { > + if (unlikely(pflags & (PF_MEMALLOC_NOIO | PF_MEMALLOC_NOFS | PF_MEMALLOC_PIN))) { > /* > - * Stronger flags before weaker flags: > - * NORECLAIM implies NOIO, which in turn implies NOFS > + * NOIO implies both NOIO and NOFS and it is a weaker context > + * so always make sure it makes precedence > */ > - if (pflags & PF_MEMALLOC_NORECLAIM) > - flags &= ~__GFP_DIRECT_RECLAIM; > - else if (pflags & PF_MEMALLOC_NOIO) > + if (pflags & PF_MEMALLOC_NOIO) > flags &= ~(__GFP_IO | __GFP_FS); > else if (pflags & PF_MEMALLOC_NOFS) > flags &= ~__GFP_FS; > > - if (pflags & PF_MEMALLOC_NOWARN) > - flags |= __GFP_NOWARN; > - > if (pflags & PF_MEMALLOC_PIN) > flags &= ~__GFP_MOVABLE; > } > -- > 2.46.0 > > > -- > Michal Hocko > SUSE Labs