Commit c0eb315a authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Linus Torvalds
Browse files

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 029c54b0 ("mm/vmalloc.c: huge-vmap:
    fail gracefully on unexpected huge vmap mappings")

[npiggin@gmail.com: sparc32: add stub pud_page define for walking huge vmalloc page tables]
  Link: https://lkml.kernel.org/r/20210324232825.1157363-1-npiggin@gmail.com

Link: https://lkml.kernel.org/r/20210317062402.533919-3-npiggin@gmail.com


Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Reviewed-by: default avatarMiaohe Lin <linmiaohe@huawei.com>
Reviewed-by: default avatarChristoph 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>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 972472c7

arch/sparc/include/asm/pgtable_32.h

+3 −0
Original line number Diff line number Diff line
@@ -321,6 +321,9 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot) 
		pgprot_val(newprot));

}



/* only used by the huge vmap code, should never be called */

#define pud_page(pud)			NULL



struct seq_file;

void mmu_info(struct seq_file *m);

mm/vmalloc.c

+26 −15
Original line number Diff line number Diff line
@@ -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 *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);