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b=FC22dvTmruFfxpWA6NszR02HUo2o/qCQ0KdUmuj7ED8Er/3uYpMui5k5QgE4IY6WQ EGmUsIR4S72LF/kMcaxN9t669WYnACus4K3IOV+2wXDFFwMsbdnn9j6NhWdl8oeNoK 8oIq+df8Y7QHFsyOauk+pIwvlmjL4AhKZcMySpOJb7iiekjHby2I3ssMur6IDNk7wV Rol8lxycOQ6UIUSMtt8Qv17v36qJhsfb8lCXSxUgvksbk4XjOzIIQQYP6qdwT8wYAW ZnvRyA4BnwmIGdqnp0Zw9OPLq5fZgBsrlzuu/bRSrfi/5d/1Ne54tIyA3r715O/wvu kNrwR26Zee/zg== Message-ID: Date: Fri, 6 Mar 2026 17:02:49 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 11/13] mm/util: Add flag to track device private pages in page snapshots To: Jordan Niethe , linux-mm@kvack.org Cc: balbirs@nvidia.com, matthew.brost@intel.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, ziy@nvidia.com, apopple@nvidia.com, lorenzo.stoakes@oracle.com, lyude@redhat.com, dakr@kernel.org, airlied@gmail.com, simona@ffwll.ch, rcampbell@nvidia.com, mpenttil@redhat.com, jgg@nvidia.com, willy@infradead.org, linuxppc-dev@lists.ozlabs.org, intel-xe@lists.freedesktop.org, jgg@ziepe.ca, Felix.Kuehling@amd.com, jhubbard@nvidia.com, maddy@linux.ibm.com, mpe@ellerman.id.au, ying.huang@linux.alibaba.com References: <20260202113642.59295-1-jniethe@nvidia.com> <20260202113642.59295-12-jniethe@nvidia.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 64ACA140010 X-Stat-Signature: ksuid6ggmbtjhfjrcwcftdokbzqy7pdz X-Rspam-User: X-HE-Tag: 1772812981-586371 X-HE-Meta: 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 yZCllOd7 BGC4wN+oOEd4My6rgMaEojmzmPo5kZHezB1PQuEJCS83SuEXyWXUelCXR6fMxvkU67+x7oRHLBXd4HqCPTOqNMD2YOy51ft1wQWrr9YKqlDPjj8s8ZZfpOgmOJMRHEXoR/fDEieBu4kE/bhIbrhOqcOjj4+8KsDFZzM/Oqme+lWRdq88P5K/OBFGmA+/By2kSTp5OvQ50QFSF7BNwlpEeiDernGPClZ/OYIFGgXzZujtxOtuvE/VNfwWIDo5TEqhCeXFSkoX8Gs26TvwsYSmHJGKMJnXWQr0MxuNN+nJuJ85N16S0RM1uwJQszsFYpNpWIxiV Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/2/26 12:36, Jordan Niethe wrote: > A future change will remove device private pages from the physical > address space. This will mean that device private pages no longer have > normal pfns and must be handled separately. > > Add a new flag PAGE_SNAPSHOT_DEVICE_PRIVATE to track when the pfn of a > page snapshot is a device private page. > > Signed-off-by: Jordan Niethe > Signed-off-by: Alistair Popple > --- > v1: > - No change > v2: > - No change > v3: > - No change > v4: > - Move logical continuation to previous line > --- > fs/proc/page.c | 6 ++++-- > include/linux/mm.h | 7 ++++--- > mm/util.c | 3 +++ > 3 files changed, 11 insertions(+), 5 deletions(-) > > diff --git a/fs/proc/page.c b/fs/proc/page.c > index f9b2c2c906cd..bc14f7ebc369 100644 > --- a/fs/proc/page.c > +++ b/fs/proc/page.c > @@ -191,10 +191,12 @@ u64 stable_page_flags(const struct page *page) > folio_test_large_rmappable(folio)) { > /* Note: we indicate any THPs here, not just PMD-sized ones */ > u |= 1 << KPF_THP; > - } else if (is_huge_zero_pfn(ps.pfn)) { > + } else if (!(ps.flags & PAGE_SNAPSHOT_DEVICE_PRIVATE) && > + is_huge_zero_pfn(ps.pfn)) { > u |= 1 << KPF_ZERO_PAGE; > u |= 1 << KPF_THP; > - } else if (is_zero_pfn(ps.pfn)) { > + } else if (!(ps.flags & PAGE_SNAPSHOT_DEVICE_PRIVATE) && > + is_zero_pfn(ps.pfn)) { > u |= 1 << KPF_ZERO_PAGE; > } > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index f0d5be9dc736..a52979536a5e 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -4627,9 +4627,10 @@ static inline bool page_pool_page_is_pp(const struct page *page) > } > #endif > > -#define PAGE_SNAPSHOT_FAITHFUL (1 << 0) > -#define PAGE_SNAPSHOT_PG_BUDDY (1 << 1) > -#define PAGE_SNAPSHOT_PG_IDLE (1 << 2) > +#define PAGE_SNAPSHOT_FAITHFUL (1 << 0) > +#define PAGE_SNAPSHOT_PG_BUDDY (1 << 1) > +#define PAGE_SNAPSHOT_PG_IDLE (1 << 2) > +#define PAGE_SNAPSHOT_DEVICE_PRIVATE (1 << 3) > > struct page_snapshot { > struct folio folio_snapshot; > diff --git a/mm/util.c b/mm/util.c > index 97cae40c0209..65e3f1a97d76 100644 > --- a/mm/util.c > +++ b/mm/util.c > @@ -1218,6 +1218,9 @@ static void set_ps_flags(struct page_snapshot *ps, const struct folio *folio, > > if (folio_test_idle(folio)) > ps->flags |= PAGE_SNAPSHOT_PG_IDLE; > + > + if (is_device_private_page(page)) > + ps->flags |= PAGE_SNAPSHOT_DEVICE_PRIVATE; stable_page_flags() has access to the page and can simply test that instead? -- Cheers, David