Patch "mm/migrate: set swap entry values of THP tail pages properly." has been added to the 5.15-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    mm/migrate: set swap entry values of THP tail pages properly.

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mm-migrate-set-swap-entry-values-of-thp-tail-pages-properly.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From stable+bounces-27000-greg=kroah.com@vger.kernel.org Wed Mar  6 16:52:16 2024
From: Zi Yan <zi.yan@sent.com>
Date: Wed,  6 Mar 2024 10:51:57 -0500
Subject: mm/migrate: set swap entry values of THP tail pages properly.
To: gregkh@linuxfoundation.org, stable@vger.kernel.org
Cc: Zi Yan <ziy@nvidia.com>, linux-mm@kvack.org, Charan Teja Kalla <quic_charante@quicinc.com>, "Matthew Wilcox (Oracle)" <willy@infradead.org>, David Hildenbrand <david@redhat.com>, Andrew Morton <akpm@linux-foundation.org>, Huang Ying <ying.huang@intel.com>, Naoya Horiguchi <naoya.horiguchi@linux.dev>
Message-ID: <20240306155157.118343-1-zi.yan@sent.com>

From: Zi Yan <ziy@nvidia.com>

The tail pages in a THP can have swap entry information stored in their
private field. When migrating to a new page, all tail pages of the new
page need to update ->private to avoid future data corruption.

This fix is stable-only, since after commit 07e09c483cbe ("mm/huge_memory:
work on folio->swap instead of page->private when splitting folio"),
subpages of a swapcached THP no longer requires the maintenance.

Adding THPs to the swapcache was introduced in commit
38d8b4e6bdc87 ("mm, THP, swap: delay splitting THP during swap out"),
where each subpage of a THP added to the swapcache had its own swapcache
entry and required the ->private field to point to the correct swapcache
entry. Later, when THP migration functionality was implemented in commit
616b8371539a6 ("mm: thp: enable thp migration in generic path"),
it initially did not handle the subpages of swapcached THPs, failing to
update their ->private fields or replace the subpage pointers in the
swapcache. Subsequently, commit e71769ae5260 ("mm: enable thp migration
for shmem thp") addressed the swapcache update aspect. This patch fixes
the update of subpage ->private fields.

Closes: https://lore.kernel.org/linux-mm/1707814102-22682-1-git-send-email-quic_charante@quicinc.com/
Fixes: 616b8371539a ("mm: thp: enable thp migration in generic path")
Signed-off-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 mm/migrate.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -424,8 +424,12 @@ int migrate_page_move_mapping(struct add
 	if (PageSwapBacked(page)) {
 		__SetPageSwapBacked(newpage);
 		if (PageSwapCache(page)) {
+			int i;
+
 			SetPageSwapCache(newpage);
-			set_page_private(newpage, page_private(page));
+			for (i = 0; i < (1 << compound_order(page)); i++)
+				set_page_private(newpage + i,
+						 page_private(page + i));
 		}
 	} else {
 		VM_BUG_ON_PAGE(PageSwapCache(page), page);


Patches currently in stable-queue which might be from kroah.com@vger.kernel.org are

queue-5.15/x86-rfds-mitigate-register-file-data-sampling-rfds.patch
queue-5.15/vfio-pci-create-persistent-intx-handler.patch
queue-5.15/x86-entry_32-add-verw-just-before-userspace-transition.patch
queue-5.15/vfio-fsl-mc-block-calling-interrupt-handler-without-trigger.patch
queue-5.15/x86-bugs-add-asm-helpers-for-executing-verw.patch
queue-5.15/x86-asm-differentiate-between-code-and-function-alignment.patch
queue-5.15/vfio-pci-disable-auto-enable-of-exclusive-intx-irq.patch
queue-5.15/vfio-pci-lock-external-intx-masking-ops.patch
queue-5.15/x86-alternatives-teach-text_poke_bp-to-patch-jcc.d32-instructions.patch
queue-5.15/vfio-introduce-interface-to-flush-virqfd-inject-workqueue.patch
queue-5.15/kvm-x86-export-rfds_no-and-rfds_clear-to-guests.patch
queue-5.15/x86-asm-add-_asm_rip-macro-for-x86-64-rip-suffix.patch
queue-5.15/x86-entry_64-add-verw-just-before-userspace-transition.patch
queue-5.15/x86-alternatives-introduce-int3_emulate_jcc.patch
queue-5.15/x86-mmio-disable-kvm-mitigation-when-x86_feature_clear_cpu_buf-is-set.patch
queue-5.15/x86-bugs-use-alternative-instead-of-mds_user_clear-static-key.patch
queue-5.15/documentation-hw-vuln-add-documentation-for-rfds.patch
queue-5.15/kvm-vmx-use-bt-jnc-i.e.-eflags.cf-to-select-vmresume-vs.-vmlaunch.patch
queue-5.15/mm-migrate-set-swap-entry-values-of-thp-tail-pages-properly.patch
queue-5.15/kvm-vmx-move-verw-closer-to-vmentry-for-mds-mitigation.patch
queue-5.15/arch-introduce-config_function_alignment.patch
queue-5.15/x86-static_call-add-support-for-jcc-tail-calls.patch
queue-5.15/vfio-platform-create-persistent-irq-handlers.patch