From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 65C0E7A15A; Mon, 26 Aug 2024 19:20:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724700014; cv=none; b=NgZ8ZxJkL5vi9iuNjQOwMIKrrGXN5kiQ/JbiyyNp+kBfa5Afwc05J54ByVAKjxIUYfBYs1Amz99xnzMesfeJ31uoa/iyfHrad751xcMqs3IU/EZ/fEYdE4vZBiciwkRMA27/Gt+JUx1LhfN/fkpppO5TBLqtm4av0WYulmjs5J0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724700014; c=relaxed/simple; bh=eTLrYsdmdBE+wLoLDRD8KNqEIQ+NOGihDOwUj8S32FE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=rrK1qgVnN9qJaGpz8aHRQJkMbC9MoITV1d+ICFAuZCN1kYWJjl/XA0lEbGfOre0P0ECEwecSJUVX7mkxLOKErNlVrnt/vPaO/YgGs+66428EGCMSRRXfKaQlh+OAUTuDZc90FmU6QglgfP4btMwy/yBJePb27m/QDQAYNWR7JE8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=JWEURzJp; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="JWEURzJp" 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> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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