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b=XMNHGDunAL2ROl6ZH05LV6ePww0er0HEGB6KXTCa1LSzaqIHkg2w+DYblTi6A4w64 nM19hkZyotNbVnUHaU4uIMKNwmgobuGOn/yFD+MCyZoQyBbVOSqYrT1Eac5WGaESfX E/VAseYRw6+B61BDDRGmni0hh5vQKFQa5OLvan1Y= Date: Mon, 18 Aug 2025 22:20:09 -0700 From: Andrew Morton To: Matthew Wilcox Cc: Boris Burkov , linux-btrfs@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, kernel-team@fb.com, shakeel.butt@linux.dev, wqu@suse.com, mhocko@kernel.org, muchun.song@linux.dev, roman.gushchin@linux.dev, hannes@cmpxchg.org Subject: Re: [PATCH v3 4/4] memcg: remove warning from folio_lruvec Message-Id: <20250818222009.7f03b557e6e1b58cb0a100ef@linux-foundation.org> In-Reply-To: References: <0cf22669a203b8671b6774408bfa4864ba3dbf60.1755562487.git.boris@bur.io> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: B0C02A000B X-Stat-Signature: 55qk9emwyh3zg5ynkj5bumwfazgh6obg X-Rspam-User: X-HE-Tag: 1755580812-627591 X-HE-Meta: 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 fPnSRYWM GqO1nClZrkPikKfg5og6gLW3sCLFbFfd72Rmge5+uTiaeQCgWZKYqdDVS7TZ06bRq+bIEBbGu3mRTnKf35iylQv4t21/KtmFwI2SseGmohO7LAHTPBGcjbLM9aGO7NBVOBb9ESNG18lWp0ESIUnYL3X18sMSSZ+a++F/f3zXQQILuuU6epW3Gb/yVNfUm5XPU5j3j65X1FMfpXOJ2RTfPuQap5sl71K+Dx4xor5EvHQpe45SUalHoJ62WRlAI4eRuJ+vr5w9bthr4XWmOc80dFFoQLgBslt+OM8JXAlFLdTgDFyu3e19n3T5VD4MlmvtP7qYwt+65+hKVZkeR4VkNXZccI1uuKKxa2LL6 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 Tue, 19 Aug 2025 03:41:30 +0100 Matthew Wilcox wrote: > On Mon, Aug 18, 2025 at 05:36:56PM -0700, Boris Burkov wrote: > > Commit a4055888629bc ("mm/memcg: warning on !memcg after readahead page > > charged") added the warning in folio_lruvec (older name was > > mem_cgroup_page_lruvec) for !memcg when charging of readahead pages were > > added to the kernel. Basically lru pages on a memcg enabled system were > > always expected to be charged to a memcg. > > > > However a recent functionality to allow metadata of btrfs, which is in > > page cache, to be uncharged is added to the kernel. We can either change > > the condition to only check anon pages or file pages which does not have > > AS_UNCHARGED in their mapping. Instead of such complicated check, let's > > just remove the warning as it is not really helpful anymore. > > This has to go before patch 3 (and I'd put it before patch 1) in order > to preserve bisectability.. Thanks, I'll move it to [2/4] ? That requires changing the tenses in the > commit message, but that's perfectly acceptable. I'm not spottig this. a4055888629bc was added in 2020 and the btrfs change is in a preceding series. I'll describe that by name, so : Commit a4055888629bc ("mm/memcg: warning on !memcg after readahead page : charged") added the warning in folio_lruvec (older name was : mem_cgroup_page_lruvec) for !memcg when charging of readahead pages were : added to the kernel. Basically lru pages on a memcg enabled system were : always expected to be charged to a memcg. : : However a recent functionality to allow metadata of btrfs, which is in : page cache, to be uncharged was added to the kernel : ("btrfs-set-as_uncharged-on-the-btree_inode.patch"). We can either change : the condition to only check anon pages or file pages which does not have : AS_UNCHARGED in their mapping. Instead of such complicated check, let's : just remove the warning as it is not really helpful anymore.