Re: [PATCH v11 01/13] mm/vmalloc: fix HUGE_VMAP regression by enabling huge pages in vmalloc_to_page
Excerpts from Ding Tianhong's message of January 28, 2021 1:13 pm:
> On 2021/1/26 12:44, Nicholas Piggin wrote:
>> 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")
>>
>> Reviewed-by: Christoph Hellwig
>> Signed-off-by: Nicholas Piggin
>> ---
>> mm/vmalloc.c | 41 ++---
>> 1 file changed, 26 insertions(+), 15 deletions(-)
>>
>> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
>> index e6f352bf0498..62372f9e0167 100644
>> --- a/mm/vmalloc.c
>> +++ b/mm/vmalloc.c
>> @@ -34,7 +34,7 @@
>> #include
>> #include
>> #include
>> -
>> +#include
>> #include
>> #include
>> #include
>> @@ -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);
>
> Hi Nicho:
>
> /builds/1mzfdQzleCy69KZFb5qHNSEgabZ/mm/vmalloc.c: In function
> 'vmalloc_to_page':
> /builds/1mzfdQzleCy69KZFb5qHNSEgabZ/include/asm-generic/pgtable-nop4d-hack.h:48:27:
> error: implicit declaration of function 'pud_page'; did you mean 'put_page'?
> [-Werror=implicit-function-declaration]
>48 | #define pgd_page(pgd)(pud_page((pud_t){ pgd }))
> | ^~~~
>
> the pug_page is not defined for aarch32 when enabling 2-level page config, it
> break the system building.
Hey thanks for finding that, not sure why that didn't trigger any CI.
Anyway newer kernels don't have the ptable-*-hack.h headers, but even so
it still breaks upstream. arm is using some hand-rolled 2-level folding
of its own (which is fair enough because most 32-bit archs were 2 level
at the time I added pgtable-nopud.h header).
This patch seems to at least make it build.
Thanks,
Nick
---
arch/arm/include/asm/pgtable-3level.h | 2 --
arch/arm/include/asm/pgtable.h| 3 +++
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/arm/include/asm/pgtable-3level.h
b/arch/arm/include/asm/pgtable-3level.h
index 2b85d175e999..d4edab51a77c 100644
--- a/arch/arm/include/asm/pgtable-3level.h
+++ b/arch/arm/include/asm/pgtable-3level.h
@@ -186,8 +186,6 @@ static inline pte_t pte_mkspecial(pte_t pte)
#define pmd_write(pmd) (pmd_isclear((pmd), L_PMD_SECT_RDONLY))
#define pmd_dirty(pmd) (pmd_isset((pmd), L_PMD_SECT_DIRTY))
-#define pud_page(pud) pmd_page(__pmd(pud_val(pud)))
-#define pud_write(pud) pmd_write(__pmd(pud_val(pud)))
#define pmd_hugewillfault(pmd) (!pmd_young(pmd) || !pmd_write(pmd))
#define pmd_thp_or_huge(pmd) (pmd_huge(pmd) || pmd_trans_huge(pmd))
diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
index c02f24400369..d63a5bb6bd0c 100644
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h
@@ -166,6 +166,9 @@ extern struct page *empty_zero_page;
extern
Re: [PATCH v11 01/13] mm/vmalloc: fix HUGE_VMAP regression by enabling huge pages in vmalloc_to_page
On 2021/1/26 12:44, Nicholas Piggin wrote:
> 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")
>
> Reviewed-by: Christoph Hellwig
> Signed-off-by: Nicholas Piggin
> ---
> mm/vmalloc.c | 41 ++---
> 1 file changed, 26 insertions(+), 15 deletions(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index e6f352bf0498..62372f9e0167 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -34,7 +34,7 @@
> #include
> #include
> #include
> -
> +#include
> #include
> #include
> #include
> @@ -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);
Hi Nicho:
/builds/1mzfdQzleCy69KZFb5qHNSEgabZ/mm/vmalloc.c: In function 'vmalloc_to_page':
/builds/1mzfdQzleCy69KZFb5qHNSEgabZ/include/asm-generic/pgtable-nop4d-hack.h:48:27:
error: implicit declaration of function 'pud_page'; did you mean 'put_page'?
[-Werror=implicit-function-declaration]
48 | #define pgd_page(pgd)(pud_page((pud_t){ pgd }))
| ^~~~
the pug_page is not defined for aarch32 when enabling 2-level page config, it
break the system building.
> + 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);
>
Re: [PATCH v11 01/13] mm/vmalloc: fix HUGE_VMAP regression by enabling huge pages in vmalloc_to_page
Hi:
On 2021/1/26 12:44, Nicholas Piggin wrote:
> 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")
>
> Reviewed-by: Christoph Hellwig
> Signed-off-by: Nicholas Piggin
> ---
> mm/vmalloc.c | 41 ++---
> 1 file changed, 26 insertions(+), 15 deletions(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index e6f352bf0498..62372f9e0167 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -34,7 +34,7 @@
> #include
> #include
> #include
> -
> +#include
> #include
> #include
> #include
> @@ -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);
>
LGTM. Thanks.
Reviewed-by: Miaohe Lin
[PATCH v11 01/13] 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")
Reviewed-by: Christoph Hellwig
Signed-off-by: Nicholas Piggin
---
mm/vmalloc.c | 41 ++---
1 file changed, 26 insertions(+), 15 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index e6f352bf0498..62372f9e0167 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -34,7 +34,7 @@
#include
#include
#include
-
+#include
#include
#include
#include
@@ -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
