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From: Shakeel Butt To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, kent.overstreet@linux.dev, vbabka@suse.cz, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, usamaarif642@gmail.com, 00107082@163.com, pasha.tatashin@soleen.com, souravpanda@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/3] alloc_tag: avoid warnings when freeing non-compound "tail" pages Message-ID: References: <20250909233409.1013367-1-surenb@google.com> <20250909233409.1013367-4-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 19114100013 X-Rspamd-Server: rspam05 X-Stat-Signature: nrcfypr4iddjhjoameqji6nfebqmrzyu X-Rspam-User: X-HE-Tag: 1757627097-396930 X-HE-Meta: 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 w3UGHoWA kOxt5zEsTiD63H3m3BVidKSk17VWPXJiJzojqISimUk5l/aLzzu8ZyXW4cUFiKDXlTtCznytyNHIjLmnNCvXHAk3/GGVytFOMMzx0SCVQ+xTdaPkd2e8HwcDn9dx2n1+jFuRwDaadqLruKEBr+3tFzXvB50jFi1lYEb7I20inUlzznM8Gh2VBhKg78BpPMNnyXYXKFrJLnlgYrVoXLRUvIIV7ajIxjXbO1CJ6a4MrjO4PaZvgw7q1iQffLdmmWU0sovt8fkXX0cMq7p86ZmhPbP+HtRe4N39J/sl3zEncbz3nw33+9dAQC7+6vB0YSAbkaRANZoPB/ao/NKNOXbduad1b0tpZ+dvoP9nI 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 Thu, Sep 11, 2025 at 01:12:11PM -0700, Suren Baghdasaryan wrote: > On Thu, Sep 11, 2025 at 1:01 PM Shakeel Butt wrote: > > > > On Tue, Sep 09, 2025 at 04:34:09PM -0700, Suren Baghdasaryan wrote: > > > When freeing "tail" pages of a non-compount high-order page, we properly > > > subtract the allocation tag counters, however later when these pages are > > > released, alloc_tag_sub() will issue warnings because tags for these pages > > > are NULL. > > > This issue was originally anticipated by Vlastimil in his review [1] and > > > then recently reported by David. > > > Prevent warnings by marking the tags empty. > > > > > > [1] https://lore.kernel.org/all/6db0f0c8-81cb-4d04-9560-ba73d63db4b8@suse.cz/ > > > > > > Suggested-by: David Wang <00107082@163.com> > > > Signed-off-by: Suren Baghdasaryan > > > --- > > > mm/page_alloc.c | 9 ++++++++- > > > 1 file changed, 8 insertions(+), 1 deletion(-) > > > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > > index 1760346bbd24..d21a411e807e 100644 > > > --- a/mm/page_alloc.c > > > +++ b/mm/page_alloc.c > > > @@ -5240,9 +5240,16 @@ static void ___free_pages(struct page *page, unsigned int order, > > > __free_frozen_pages(page, order, fpi_flags); > > > else if (!head) { > > > pgalloc_tag_sub_pages(tag, (1 << order) - 1); > > > - while (order-- > 0) > > > + while (order-- > 0) { > > > + /* > > > + * The "tail" pages of this non-compound high-order > > > + * page will have no code tags, so to avoid warnings > > > + * mark them as empty. > > > + */ > > > + clear_page_tag_ref(page + (1 << order)); > > > > Do we need something similar for the release_pages() code path or is it > > happening already? > > Pages released with release_pages() should have valid tags, so I > expect no warnings. > Oh so this is orthogonal to your first patch which is replacing __free_page with release_pages(). This non-compound high-order page is not an issue in the codepath vm_module_tags_populate(), correct?