mm/gup: check p4d presence before going on

Currently there should have no p4d swap entries so it may not matter much,
however this may help us to rule out swap entries in pXd_huge() API, which
will include p4d_huge().  The p4d_present() checks make it 100% clear that
we won't rely on p4d_huge() for swap entries.

Link: https://lkml.kernel.org/r/20240318200404.448346-4-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bjorn Andersson <andersson@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Fabio Estevam <festevam@denx.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Konrad Dybcio <konrad.dybcio@linaro.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Mark Salter <msalter@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/gup.c b/mm/gup.c
index 19f6a458683d45a312afdc783ecdb38f5740fd1f..7ed2c99fb72c9d6446ff75caf8299d6e34754a0f 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -776,7 +776,7 @@ static struct page *follow_p4d_mask(struct vm_area_struct *vma,
 
        p4dp = p4d_offset(pgdp, address);
        p4d = READ_ONCE(*p4dp);
-       if (p4d_none(p4d))
+       if (!p4d_present(p4d))
                return no_page_table(vma, flags);
        BUILD_BUG_ON(p4d_huge(p4d));
        if (unlikely(p4d_bad(p4d)))
@@ -3081,7 +3081,7 @@ static int gup_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr, unsigned lo
                p4d_t p4d = READ_ONCE(*p4dp);
 
                next = p4d_addr_end(addr, end);
-               if (p4d_none(p4d))
+               if (!p4d_present(p4d))
                        return 0;
                BUILD_BUG_ON(p4d_huge(p4d));
                if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {