+ xen-grant-table-stop-setting-pg_private-on-pages-for-grant-mapping.patch added to mm-new branch

+ xen-grant-table-stop-setting-pg_private-on-pages-for-grant-mapping.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: xen/grant-table: stop setting PG_private on pages for grant mapping
has been added to the -mm mm-new branch.  Its filename is
     xen-grant-table-stop-setting-pg_private-on-pages-for-grant-mapping.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/xen-grant-table-stop-setting-pg_private-on-pages-for-grant-mapping.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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   b) Prefer to cc a suitable mailing list as well
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

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and is updated there most days

------------------------------------------------------
From: Zi Yan <ziy@nvidia.com>
Subject: xen/grant-table: stop setting PG_private on pages for grant mapping
Date: Sun, 13 Sep 2026 22:24:01 -0400

gnttab_alloc_pages() stores xen_page_foreign in page->private.  On 32-bit,
a pointer to an allocated xen_page_foreign is stored; on 64-bit,
xen_page_foreign is stored inline.  Checking page->private != NULL is
enough to tell whether a xen_page_foreign needs to be freed on 32-bit and
page->private is zeroed unconditionally on 64-bit.

It prepares for a future commit that remove PG_private.

No functional change intended.

Assisted-by: LLM
Link: https://lore.kernel.org/20260913-remove-pg_private-v4-3-848550f7574e@nvidia.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
---

 drivers/xen/grant-table.c |   11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

--- a/drivers/xen/grant-table.c~xen-grant-table-stop-setting-pg_private-on-pages-for-grant-mapping
+++ a/drivers/xen/grant-table.c
@@ -863,10 +863,10 @@ EXPORT_SYMBOL_GPL(gnttab_free_auto_xlat_
 
 int gnttab_pages_set_private(int nr_pages, struct page **pages)
 {
+#if BITS_PER_LONG < 64
 	int i;
 
 	for (i = 0; i < nr_pages; i++) {
-#if BITS_PER_LONG < 64
 		struct xen_page_foreign *foreign;
 
 		foreign = kzalloc_obj(*foreign);
@@ -874,9 +874,9 @@ int gnttab_pages_set_private(int nr_page
 			return -ENOMEM;
 
 		set_page_private(pages[i], (unsigned long)foreign);
-#endif
-		SetPagePrivate(pages[i]);
 	}
+#endif
+	/* Data is stored in page->private on 64-bit */
 
 	return 0;
 }
@@ -1031,12 +1031,11 @@ void gnttab_pages_clear_private(int nr_p
 	int i;
 
 	for (i = 0; i < nr_pages; i++) {
-		if (PagePrivate(pages[i])) {
 #if BITS_PER_LONG < 64
+		if (page_private(pages[i]))
 			kfree((void *)page_private(pages[i]));
 #endif
-			ClearPagePrivate(pages[i]);
-		}
+		set_page_private(pages[i], 0);
 	}
 }
 EXPORT_SYMBOL_GPL(gnttab_pages_clear_private);
_

Patches currently in -mm which might be from ziy@nvidia.com are

mm-zsmalloc-replace-pg_private-with-pointer-comparison.patch
perf-ring_buffer-stop-using-pg_private-as-aux-page-high-order-marker.patch
xen-grant-table-stop-setting-pg_private-on-pages-for-grant-mapping.patch
fscrypt-stop-setting-pg_private-on-bounce-page.patch
mm-hugetlb-use-direct-assignment-instead-of-folio_change_private.patch
f2fs-stop-using-pg_private.patch
f2fs-convert-the-private-flag-helpers-to-folio-only.patch
erofs-mm-pagemap-add-readahead_folio_last-to-avoid-folio-private.patch
erofs-use-folio_attach-detach_private-instead-of-direct-assignment.patch
mm-page-flags-check-page-folio-private-instead-of-pg_private.patch
treewide-remove-folio_set-clear_private-usage.patch
ceph-replace-pageprivate-with-page_private.patch
md-md-bitmap-replace-pageprivate-with-page_private.patch
buffer-replace-page_buffer-with-page_private-and-delete-it.patch
treewide-remove-pageprivate-and-pg_private-from-comments-and-docs.patch
mm-page-flags-remove-pg_private.patch
usb-gadgetfs-do-not-warn-about-excessively-large-memory-allocations.patch