[PATCH 6.1 106/118] mm: extend max struct page size for kmsan

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

From: Arnd Bergmann <arnd@xxxxxxxx>

commit 3770e52fd4ec40ebee16ba19ad6c09dc0b52739b upstream.

After x86 enabled support for KMSAN, it has become possible to have larger
'struct page' than was expected when commit 5470dea49f53 ("mm: use
mm_zero_struct_page from SPARC on all 64b architectures") was merged:

include/linux/mm.h:156:10: warning: no case matching constant switch condition '96'
        switch (sizeof(struct page)) {

Extend the maximum accordingly.

Link: https://lkml.kernel.org/r/20230130130739.563628-1-arnd@xxxxxxxxxx
Fixes: 5470dea49f53 ("mm: use mm_zero_struct_page from SPARC on all 64b architectures")
Fixes: 4ca8cc8d1bbe ("x86: kmsan: enable KMSAN builds for x86")
Fixes: f80be4571b19 ("kmsan: add KMSAN runtime core")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Reviewed-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Alex Sierra <alex.sierra@xxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 include/linux/mm.h |   12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -136,7 +136,7 @@ extern int mmap_rnd_compat_bits __read_m
  * define their own version of this macro in <asm/pgtable.h>
  */
 #if BITS_PER_LONG == 64
-/* This function must be updated when the size of struct page grows above 80
+/* This function must be updated when the size of struct page grows above 96
  * or reduces below 56. The idea that compiler optimizes out switch()
  * statement, and only leaves move/store instructions. Also the compiler can
  * combine write statements if they are both assignments and can be reordered,
@@ -147,12 +147,18 @@ static inline void __mm_zero_struct_page
 {
 	unsigned long *_pp = (void *)page;
 
-	 /* Check that struct page is either 56, 64, 72, or 80 bytes */
+	 /* Check that struct page is either 56, 64, 72, 80, 88 or 96 bytes */
 	BUILD_BUG_ON(sizeof(struct page) & 7);
 	BUILD_BUG_ON(sizeof(struct page) < 56);
-	BUILD_BUG_ON(sizeof(struct page) > 80);
+	BUILD_BUG_ON(sizeof(struct page) > 96);
 
 	switch (sizeof(struct page)) {
+	case 96:
+		_pp[11] = 0;
+		fallthrough;
+	case 88:
+		_pp[10] = 0;
+		fallthrough;
 	case 80:
 		_pp[9] = 0;
 		fallthrough;