+ mm-vmalloc-fix-huge_vmap-regression-by-enabling-huge-pages-in-vmalloc_to_page.patch added to -mm tree

+ mm-vmalloc-fix-huge_vmap-regression-by-enabling-huge-pages-in-vmalloc_to_page.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm/vmalloc: fix HUGE_VMAP regression by enabling huge pages in vmalloc_to_page
has been added to the -mm tree.  Its filename is
     mm-vmalloc-fix-huge_vmap-regression-by-enabling-huge-pages-in-vmalloc_to_page.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-vmalloc-fix-huge_vmap-regression-by-enabling-huge-pages-in-vmalloc_to_page.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-vmalloc-fix-huge_vmap-regression-by-enabling-huge-pages-in-vmalloc_to_page.patch

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------------------------------------------------------
From: Nicholas Piggin <npiggin@gmail.com>
Subject: mm/vmalloc: fix HUGE_VMAP regression by enabling huge pages in vmalloc_to_page

vmalloc_to_page returns NULL for addresses mapped by larger pages[*]. 
Whether or not a vmap is huge depends on the architecture details,
alignments, boot options, etc., which the caller can not be expected to
know.  Therefore HUGE_VMAP is a regression for vmalloc_to_page.

This change teaches vmalloc_to_page about larger pages, and returns the
struct page that corresponds to the offset within the large page.  This
makes the API agnostic to mapping implementation details.

[*] As explained by commit 029c54b095995 ("mm/vmalloc.c: huge-vmap:
    fail gracefully on unexpected huge vmap mappings")

Link: https://lkml.kernel.org/r/20210317062402.533919-3-npiggin@gmail.com
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ding Tianhong <dingtianhong@huawei.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmalloc.c |   41 ++++++++++++++++++++++++++---------------
 1 file changed, 26 insertions(+), 15 deletions(-)

--- a/mm/vmalloc.c~mm-vmalloc-fix-huge_vmap-regression-by-enabling-huge-pages-in-vmalloc_to_page
+++ a/mm/vmalloc.c
@@ -34,7 +34,7 @@
 #include <linux/bitops.h>
 #include <linux/rbtree_augmented.h>
 #include <linux/overflow.h>
-
+#include <linux/pgtable.h>
 #include <linux/uaccess.h>
 #include <asm/tlbflush.h>
 #include <asm/shmparam.h>
@@ -343,7 +343,9 @@ int is_vmalloc_or_module_addr(const void
 }
 
 /*
- * Walk a vmap address to the struct page it maps.
+ * Walk a vmap address to the struct page it maps. Huge vmap mappings will
+ * return the tail page that corresponds to the base page address, which
+ * matches small vmap mappings.
  */
 struct page *vmalloc_to_page(const void *vmalloc_addr)
 {
@@ -363,25 +365,33 @@ struct page *vmalloc_to_page(const void
 
 	if (pgd_none(*pgd))
 		return NULL;
+	if (WARN_ON_ONCE(pgd_leaf(*pgd)))
+		return NULL; /* XXX: no allowance for huge pgd */
+	if (WARN_ON_ONCE(pgd_bad(*pgd)))
+		return NULL;
+
 	p4d = p4d_offset(pgd, addr);
 	if (p4d_none(*p4d))
 		return NULL;
-	pud = pud_offset(p4d, addr);
+	if (p4d_leaf(*p4d))
+		return p4d_page(*p4d) + ((addr & ~P4D_MASK) >> PAGE_SHIFT);
+	if (WARN_ON_ONCE(p4d_bad(*p4d)))
+		return NULL;
 
-	/*
-	 * Don't dereference bad PUD or PMD (below) entries. This will also
-	 * identify huge mappings, which we may encounter on architectures
-	 * that define CONFIG_HAVE_ARCH_HUGE_VMAP=y. Such regions will be
-	 * identified as vmalloc addresses by is_vmalloc_addr(), but are
-	 * not [unambiguously] associated with a struct page, so there is
-	 * no correct value to return for them.
-	 */
-	WARN_ON_ONCE(pud_bad(*pud));
-	if (pud_none(*pud) || pud_bad(*pud))
+	pud = pud_offset(p4d, addr);
+	if (pud_none(*pud))
+		return NULL;
+	if (pud_leaf(*pud))
+		return pud_page(*pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
+	if (WARN_ON_ONCE(pud_bad(*pud)))
 		return NULL;
+
 	pmd = pmd_offset(pud, addr);
-	WARN_ON_ONCE(pmd_bad(*pmd));
-	if (pmd_none(*pmd) || pmd_bad(*pmd))
+	if (pmd_none(*pmd))
+		return NULL;
+	if (pmd_leaf(*pmd))
+		return pmd_page(*pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
+	if (WARN_ON_ONCE(pmd_bad(*pmd)))
 		return NULL;
 
 	ptep = pte_offset_map(pmd, addr);
@@ -389,6 +399,7 @@ struct page *vmalloc_to_page(const void
 	if (pte_present(pte))
 		page = pte_page(pte);
 	pte_unmap(ptep);
+
 	return page;
 }
 EXPORT_SYMBOL(vmalloc_to_page);
_

Patches currently in -mm which might be from npiggin@gmail.com are

arm-mm-add-missing-pud_page-define-to-2-level-page-tables.patch
mm-vmalloc-fix-huge_vmap-regression-by-enabling-huge-pages-in-vmalloc_to_page.patch
mm-apply_to_pte_range-warn-and-fail-if-a-large-pte-is-encountered.patch
mm-vmalloc-rename-vmap__range-vmap_pages__range.patch
mm-ioremap-rename-ioremap__range-to-vmap__range.patch
mm-huge_vmap-arch-support-cleanup.patch
powerpc-inline-huge-vmap-supported-functions.patch
arm64-inline-huge-vmap-supported-functions.patch
x86-inline-huge-vmap-supported-functions.patch
mm-vmalloc-provide-fallback-arch-huge-vmap-support-functions.patch
mm-move-vmap_range-from-mm-ioremapc-to-mm-vmallocc.patch
mm-vmalloc-add-vmap_range_noflush-variant.patch
mm-vmalloc-hugepage-vmalloc-mappings.patch
powerpc-64s-radix-enable-huge-vmalloc-mappings.patch