From: Nicholas Piggin <npiggin@gmail.com>
To: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>
Cc: Nicholas Piggin <npiggin@gmail.com>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, Zefan Li <lizefan@huawei.com>,
Jonathan Cameron <Jonathan.Cameron@Huawei.com>,
Christoph Hellwig <hch@infradead.org>,
Christophe Leroy <christophe.leroy@csgroup.eu>
Subject: [PATCH v6 01/12] mm/vmalloc: fix vmalloc_to_page for huge vmap mappings
Date: Sat, 22 Aug 2020 01:12:05 +1000 [thread overview]
Message-ID: <20200821151216.1005117-2-npiggin@gmail.com> (raw)
In-Reply-To: <20200821151216.1005117-1-npiggin@gmail.com>
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")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
mm/vmalloc.c | 41 ++++++++++++++++++++++++++---------------
1 file changed, 26 insertions(+), 15 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index b482d240f9a2..4e9b21adc73d 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -36,7 +36,7 @@
#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 *x)
}
/*
- * 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 *vmalloc_addr)
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 *vmalloc_addr)
if (pte_present(pte))
page = pte_page(pte);
pte_unmap(ptep);
+
return page;
}
EXPORT_SYMBOL(vmalloc_to_page);
--
2.23.0
next prev parent reply other threads:[~2020-08-21 15:12 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-21 15:12 [PATCH v6 00/12] huge vmalloc mappings Nicholas Piggin
2020-08-21 15:12 ` Nicholas Piggin [this message]
2020-08-21 20:07 ` [PATCH v6 01/12] mm/vmalloc: fix vmalloc_to_page for huge vmap mappings Andrew Morton
2020-08-21 22:42 ` Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 02/12] mm: apply_to_pte_range warn and fail if a large pte is encountered Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 03/12] mm/vmalloc: rename vmap_*_range vmap_pages_*_range Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 04/12] mm/ioremap: rename ioremap_*_range to vmap_*_range Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 05/12] mm: HUGE_VMAP arch support cleanup Nicholas Piggin
2020-08-21 20:14 ` Andrew Morton
2020-08-21 22:45 ` Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 06/12] powerpc: inline huge vmap supported functions Nicholas Piggin
2020-08-21 20:15 ` Andrew Morton
2020-08-21 15:12 ` [PATCH v6 07/12] arm64: " Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 08/12] x86: " Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 09/12] mm: Move vmap_range from mm/ioremap.c to mm/vmalloc.c Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 10/12] mm/vmalloc: add vmap_range_noflush variant Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 11/12] mm/vmalloc: Hugepage vmalloc mappings Nicholas Piggin
2020-08-21 15:38 ` Eric Dumazet
2020-08-21 16:05 ` Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 12/12] powerpc/64s/radix: Enable huge " Nicholas Piggin
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