From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-pj1-x1031.google.com ([2607:f8b0:4864:20::1031]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1n24hb-000Cfo-M9 for kexec@lists.infradead.org; Tue, 28 Dec 2021 05:07:13 +0000 Received: by mail-pj1-x1031.google.com with SMTP id lr15-20020a17090b4b8f00b001b19671cbebso16064866pjb.1 for ; Mon, 27 Dec 2021 21:07:06 -0800 (PST) Date: Tue, 28 Dec 2021 05:06:58 +0000 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> Subject: Re: [PATCH v4 3/3] mm/page_alloc.c: do not warn allocation failure on zone DMA if no managed pages Message-ID: <20211228050658.GA2115590@odroid> References: <20211223094435.248523-1-bhe@redhat.com> <20211223094435.248523-4-bhe@redhat.com> <20211227083253.GA24172@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20211227083253.GA24172@MiWiFi-R3L-srv> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Baoquan He Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, hch@lst.de, cl@linux.com, John.p.donnelly@oracle.com, kexec@lists.infradead.org, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, vbabka@suse.cz, David.Laight@aculab.com, david@redhat.com, x86@kernel.org, bp@alien8.de On Mon, Dec 27, 2021 at 04:32:53PM +0800, Baoquan He wrote: > On 12/25/21 at 05:53am, Hyeonggon Yoo wrote: > > On Thu, Dec 23, 2021 at 05:44:35PM +0800, Baoquan He wrote: > ...... > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > > index 7c7a0b5de2ff..843bc8e5550a 100644 > > > --- a/mm/page_alloc.c > > > +++ b/mm/page_alloc.c > > > @@ -4204,7 +4204,8 @@ void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...) > > > va_list args; > > > static DEFINE_RATELIMIT_STATE(nopage_rs, 10*HZ, 1); > > > > > > - if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs)) > > > + if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs) || > > > + (gfp_mask & __GFP_DMA) && !has_managed_dma()) > > > return; > > > > > > > Warning when there's always no page in DMA zone is unnecessary > > and it confuses user. > > > > The patch looks good. > > Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> > > > > And there is some driers that allocate memory with GFP_DMA > > even if that flag is unnecessary. We need to do cleanup later. > > Thanks for reviewing and giving out some awesome suggestions. > You're welcome. Impressed to see you keep following the issue. > > > > Baoquan Are you planning to do it soon? > > I want to help that. > > Yes, I had the plan and have done a little part. I talked to Christoph > about my thought. I planned to collect all kmalloc(GFP_DMA) callsite and > post a RFC mail, CC mailing list and maintainers related. Anyone > interested or know one or several callsites well can help. > Good to hear that. I want to help by reviewing and discussing your patches. > Now, Christoph has handled all under drviers/scsi, and post patches to > fix them. Oh, didn't know he was already doing that work. > I have gone throug those places and found out below callsites > where we can remove GFP_DMA directly when calling kmalloc() since not > necessary. Note that some of them might have 24bit addressing limitation. we need to ask maintainer or read its specification to know GFP_DMA is unnecessary. > And even found one place kmalloc(GFP_DMA32). kmalloc(GFP_DMA32) is wrong because we do not create DMA32 kmalloc caches. > (HEAD -> master) vxge: don't use GFP_DMA > mtd: rawnand: marvell: don't use GFP_DMA > HID: intel-ish-hid: remove wrong GFP_DMA32 flag > ps3disk: don't use GFP_DMA > atm: iphase: don't use GFP_DMA > Next, I will send a RFC mail to contain those suspect callsites. We can > track them and can help if needed. Suggest to change them with: > 1) using dma_alloc_xx , or dma_map_xx after kmalloc() > 2) using alloc_pages(GFP_DMA) instead Well if the buffer is not sensitive to performance, we can just allocate with kmalloc(GFP_KERNEL) so that dma api can use proper bounce buffer. if the buffer is for fastpath, I think we should convert them to use dma_alloc_pages() to get a proper buffer. Note that most of devices are already calling dma_map_xx directly or indirectly (think about block layer for example) if they don't use deprecated virt_to_bus() or friends. But if the device do not use DMA API at all, we have few choices. maybe convert them to use alloc_pages(GFP_DMA/GFP_DMA32) I guess? > When we fix, we all post patch with subject key words as > 'xxxx: don't use GFP_DMA'. Christoph has posted patch with the similar > subject, we can search subject to get all related patches for later back > porting. > > I will add you to CC when sending. Could be tomorrow. Any suggestion or thought? > > Thanks > Baoquan > Thank you! Hyeonggon _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec