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@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
arch/powerpc/sysdev/axonram.c | 2 +-
drivers/s390/block/dcssblk.c | 3 ++-
include/linux/pfn_t.h | 13 +++++++++++++
mm/memory.c | 16 +++++++++++++++-
4 files changed, 31 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/sysdev/axonram.c b/arch/powerpc/sysdev/axonram.c
index c60e84e4558d..aaf540efb92c 100644
--- a/arch/powerpc/sysdev/axonram.c
+++ b/arch/powerpc/sysdev/axonram.c
@@ -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;
}
diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
index 7abb240847c0..87756e28c29b 100644
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -915,7 +915,8 @@ __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;
}
diff --git a/include/linux/pfn_t.h b/include/linux/pfn_t.h
index a49b3259cad7..2a16386725b2 100644
--- a/include/linux/pfn_t.h
+++ b/include/linux/pfn_t.h
@@ -14,8 +14,10 @@
#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" }, \
@@ -119,4 +121,15 @@ 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_ */
diff --git a/mm/memory.c b/mm/memory.c
index a728bed16c20..e764dc5d8a87 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1896,12 +1896,26 @@ 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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