Commit 785a3fab authored by Dan Williams's avatar Dan Williams
Browse files

mm, dax: introduce pfn_t_special() 



In support of removing the VM_MIXEDMAP indication from DAX VMAs,
introduce pfn_t_special() for drivers to indicate that _PAGE_SPECIAL
should be used for DAX ptes. This also helps identify drivers like
dccssblk that only want to use DAX in a read-only fashion without
get_user_pages() support.

Ideally we could delete axonram and dcssblk DAX support, but if we need
to keep it better make it explicit that axonram and dcssblk only support
a sub-set of DAX due to missing _PAGE_DEVMAP support.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent 77dd66a3

arch/powerpc/sysdev/axonram.c

+1 −1
Original line number Diff line number Diff line
@@ -151,7 +151,7 @@ __axon_ram_direct_access(struct axon_ram_bank *bank, pgoff_t pgoff, long nr_page 
	resource_size_t offset = pgoff * PAGE_SIZE;



	*kaddr = (void *) bank->io_addr + offset;

	*pfn = phys_to_pfn_t(bank->ph_addr + offset, PFN_DEV);

	*pfn = phys_to_pfn_t(bank->ph_addr + offset, PFN_DEV|PFN_SPECIAL);

	return (bank->size - offset) / PAGE_SIZE;

}

drivers/s390/block/dcssblk.c

+2 −1
Original line number Diff line number Diff line
@@ -916,7 +916,8 @@ __dcssblk_direct_access(struct dcssblk_dev_info *dev_info, pgoff_t pgoff, 


	dev_sz = dev_info->end - dev_info->start + 1;

	*kaddr = (void *) dev_info->start + offset;

	*pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset), PFN_DEV);

	*pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset),

			PFN_DEV|PFN_SPECIAL);



	return (dev_sz - offset) / PAGE_SIZE;

}

include/linux/pfn_t.h

+13 −0
Original line number Diff line number Diff line
@@ -15,8 +15,10 @@ 
#define PFN_SG_LAST (1ULL << (BITS_PER_LONG_LONG - 2))

#define PFN_DEV (1ULL << (BITS_PER_LONG_LONG - 3))

#define PFN_MAP (1ULL << (BITS_PER_LONG_LONG - 4))

#define PFN_SPECIAL (1ULL << (BITS_PER_LONG_LONG - 5))



#define PFN_FLAGS_TRACE \

	{ PFN_SPECIAL,	"SPECIAL" }, \

	{ PFN_SG_CHAIN,	"SG_CHAIN" }, \

	{ PFN_SG_LAST,	"SG_LAST" }, \

	{ PFN_DEV,	"DEV" }, \
@@ -120,4 +122,15 @@ pud_t pud_mkdevmap(pud_t pud); 
#endif

#endif /* __HAVE_ARCH_PTE_DEVMAP */



#ifdef __HAVE_ARCH_PTE_SPECIAL

static inline bool pfn_t_special(pfn_t pfn)

{

	return (pfn.val & PFN_SPECIAL) == PFN_SPECIAL;

}

#else

static inline bool pfn_t_special(pfn_t pfn)

{

	return false;

}

#endif /* __HAVE_ARCH_PTE_SPECIAL */

#endif /* _LINUX_PFN_T_H_ */

mm/memory.c

+15 −1
Original line number Diff line number Diff line
@@ -1897,12 +1897,26 @@ int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr, 
}

EXPORT_SYMBOL(vm_insert_pfn_prot);



static bool vm_mixed_ok(struct vm_area_struct *vma, pfn_t pfn)

{

	/* these checks mirror the abort conditions in vm_normal_page */

	if (vma->vm_flags & VM_MIXEDMAP)

		return true;

	if (pfn_t_devmap(pfn))

		return true;

	if (pfn_t_special(pfn))

		return true;

	if (is_zero_pfn(pfn_t_to_pfn(pfn)))

		return true;

	return false;

}



static int __vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,

			pfn_t pfn, bool mkwrite)

{

	pgprot_t pgprot = vma->vm_page_prot;



	BUG_ON(!(vma->vm_flags & VM_MIXEDMAP));

	BUG_ON(!vm_mixed_ok(vma, pfn));



	if (addr < vma->vm_start || addr >= vma->vm_end)

		return -EFAULT;

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