This is a note to let you know that I've just added the patch titled
mm: split huge PUD on wp_huge_pud fallback
to the 5.18-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-split-huge-pud-on-wp_huge_pud-fallback.patch
and it can be found in the queue-5.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 14c99d65941538aa33edd8dc7b1bbbb593c324a2 Mon Sep 17 00:00:00 2001
From: "Gowans, James" <jgowans@xxxxxxxxxx>
Date: Thu, 23 Jun 2022 05:24:03 +0000
Subject: mm: split huge PUD on wp_huge_pud fallback
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
From: Gowans, James <jgowans@xxxxxxxxxx>
commit 14c99d65941538aa33edd8dc7b1bbbb593c324a2 upstream.
Currently the implementation will split the PUD when a fallback is taken
inside the create_huge_pud function. This isn't where it should be done:
the splitting should be done in wp_huge_pud, just like it's done for PMDs.
Reason being that if a callback is taken during create, there is no PUD
yet so nothing to split, whereas if a fallback is taken when encountering
a write protection fault there is something to split.
It looks like this was the original intention with the commit where the
splitting was introduced, but somehow it got moved to the wrong place
between v1 and v2 of the patch series. Rebase mistake perhaps.
Link: https://lkml.kernel.org/r/6f48d622eb8bce1ae5dd75327b0b73894a2ec407.camel@xxxxxxxxxx
Fixes: 327e9fd48972 ("mm: Split huge pages on write-notify or COW")
Signed-off-by: James Gowans <jgowans@xxxxxxxxxx>
Reviewed-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Cc: Christian König <christian.koenig@xxxxxxx>
Cc: Jan H. Schönherr <jschoenh@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 27 ++++++++++++++-------------
1 file changed, 14 insertions(+), 13 deletions(-)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4528,6 +4528,19 @@ static vm_fault_t create_huge_pud(struct
defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
/* No support for anonymous transparent PUD pages yet */
if (vma_is_anonymous(vmf->vma))
+ return VM_FAULT_FALLBACK;
+ if (vmf->vma->vm_ops->huge_fault)
+ return vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PUD);
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+ return VM_FAULT_FALLBACK;
+}
+
+static vm_fault_t wp_huge_pud(struct vm_fault *vmf, pud_t orig_pud)
+{
+#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && \
+ defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
+ /* No support for anonymous transparent PUD pages yet */
+ if (vma_is_anonymous(vmf->vma))
goto split;
if (vmf->vma->vm_ops->huge_fault) {
vm_fault_t ret = vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PUD);
@@ -4538,19 +4551,7 @@ static vm_fault_t create_huge_pud(struct
split:
/* COW or write-notify not handled on PUD level: split pud.*/
__split_huge_pud(vmf->vma, vmf->pud, vmf->address);
-#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
- return VM_FAULT_FALLBACK;
-}
-
-static vm_fault_t wp_huge_pud(struct vm_fault *vmf, pud_t orig_pud)
-{
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- /* No support for anonymous transparent PUD pages yet */
- if (vma_is_anonymous(vmf->vma))
- return VM_FAULT_FALLBACK;
- if (vmf->vma->vm_ops->huge_fault)
- return vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PUD);
-#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE && CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
return VM_FAULT_FALLBACK;
}
Patches currently in stable-queue which might be from jgowans@xxxxxxxxxx are
queue-5.18/mm-split-huge-pud-on-wp_huge_pud-fallback.patch
