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[109.81.31.109]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b723fb057e5sm410190966b.57.2025.11.05.00.05.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Nov 2025 00:05:04 -0800 (PST) Date: Wed, 5 Nov 2025 09:05:02 +0100 From: Michal Hocko To: libaokun@huaweicloud.com Cc: linux-mm@kvack.org, akpm@linux-foundation.org, vbabka@suse.cz, surenb@google.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, willy@infradead.org, shakeel.butt@linux.dev, jack@suse.cz, yi.zhang@huawei.com, yangerkun@huawei.com, libaokun1@huawei.com Subject: Re: [PATCH] mm/page_alloc: don't warn about large allocations with __GFP_NOFAIL Message-ID: References: <20251105074106.3508870-1-libaokun@huaweicloud.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251105074106.3508870-1-libaokun@huaweicloud.com> X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: E24EBA000D X-Stat-Signature: wu1zg6w1u6q1frstfw4k5xga3784igd6 X-HE-Tag: 1762329905-229487 X-HE-Meta: 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 qdRig0rW 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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 Wed 05-11-25 15:41:06, libaokun@huaweicloud.com wrote: > From: Baokun Li > > Filesystems use __GFP_NOFAIL to allocate block-sized folios for metadata > reads at critical points, since they cannot afford to go read-only, > shut down, or enter an inconsistent state due to memory pressure. > > Currently, attempting to allocate page units greater than order-1 with > the __GFP_NOFAIL flag triggers a WARN_ON() in __alloc_pages_slowpath(). > However, filesystems supporting large block sizes (blocksize > PAGE_SIZE) > can easily require allocations larger than order-1. > > As Matthew Wilcox noted, if we have a filesystem with 64KiB sectors, there > will be many clean folios in the page cache that are 64KiB or larger. > > With gfp flags and order already included in the OOM report, both > Vlastimil Babka and Michal Hocko suggested that we can take the risk of > removing this warning first and then observe whether a large number of > related OOM reports appear. > > If that happens, we can consider adding special handling in other places. > > Suggested-by: Matthew Wilcox > Link: https://lore.kernel.org/all/aQPX1-XWQjKaMTZB@casper.infradead.org > Suggested-by: Vlastimil Babka > Link: https://lore.kernel.org/all/188a95ba-6384-4319-bb74-c0d9ec6c4079@suse.cz > Suggested-by: Michal Hocko > Link: https://lore.kernel.org/all/aQotQBjnDDeL_wHx@tiehlicka > Signed-off-by: Baokun Li Thanks for referencing above links which are providing a useful insight for future reference. I would just add a link to Matthew explanation why kvmalloc is not an option Link: https://lore.kernel.org/all/aQTHMI3t5mNXp0M1@casper.infradead.org/T/#u Acked-by: Michal Hocko > --- > > RFC: https://lore.kernel.org/all/20251031061350.2052509-1-libaokun@huaweicloud.com > > mm/page_alloc.c | 5 ----- > 1 file changed, 5 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index fb91c566327c..e4efda1158b2 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -4683,11 +4683,6 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, > int reserve_flags; > > if (unlikely(nofail)) { > - /* > - * We most definitely don't want callers attempting to > - * allocate greater than order-1 page units with __GFP_NOFAIL. > - */ > - WARN_ON_ONCE(order > 1); > /* > * Also we don't support __GFP_NOFAIL without __GFP_DIRECT_RECLAIM, > * otherwise, we may result in lockup. > -- > 2.46.1 -- Michal Hocko SUSE Labs