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Thu, 11 Sep 2025 14:51:36 -0700 (PDT) MIME-Version: 1.0 References: <20250909233409.1013367-1-surenb@google.com> <20250909233409.1013367-4-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Thu, 11 Sep 2025 14:51:25 -0700 X-Gm-Features: AS18NWAYJD7p3_wAWHt6t9BtXnrobKcobygiyfTNh5kX10qBbZB119SkJzlYs_E Message-ID: Subject: Re: [PATCH 3/3] alloc_tag: avoid warnings when freeing non-compound "tail" pages To: Shakeel Butt 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: B92DD40005 X-Stat-Signature: px1mup83k8qnunugaqm8g8awfrce3izh X-HE-Tag: 1757627497-382929 X-HE-Meta: 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 nH0XsqLP 8idZrEgmIQnGCf8ApXfd+2Mc6SF9fgCm8lAh6mTXhjX/S2Z9/SuNRd0d5VA0ilZ24nIdpcxqMqjWQ4rWfDmQW1lPrup/UOSQqf4vZSyQ4ncm2+Mfb+UGMSKTTxcZW6XCXdavIsTEZSX5gLtFdUdunTa7gfQlS6eCu1MXPXz3Hv5QlwEoqpumhVWMIPixmBwcrvm4sZ1oYgt00KaLRr+yBpgFK/+m4YParJkH3VgajsmZzgVmVMHifhqWuD86PhzN+3coCzFQ5zPX/JU0VCuYxW6P3YXpZ5dLGJcD7ofmuz8kuwKkUnfDccr9FHg== 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 2:45=E2=80=AFPM Shakeel Butt wrote: > > On Thu, Sep 11, 2025 at 01:12:11PM -0700, Suren Baghdasaryan wrote: > > On Thu, Sep 11, 2025 at 1:01=E2=80=AFPM 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 pro= perly > > > > subtract the allocation tag counters, however later when these page= s are > > > > released, alloc_tag_sub() will issue warnings because tags for thes= e 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-ba73d63db4b= 8@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 w= arnings > > > > + * 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? Yes, these are independent fixes.