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Subject[PATCH 1/7] mm, x86, PAT: rework linear pfn-mmap tracking
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This patch replaces generic vma-flag VM_PFN_AT_MMAP with x86-only VM_PAT.

We can toss mapping address from remap_pfn_range() into track_pfn_vma_new(),
and collect all PAT-related logic together in arch/x86/.

This patch also restores orignal frustration-free is_cow_mapping() check in
remap_pfn_range(), as it was before commit v2.6.28-rc8-88-g3c8bb73
("x86: PAT: store vm_pgoff for all linear_over_vma_region mappings - v3")

is_linear_pfn_mapping() checks can be removed from mm/huge_memory.c,
because it already handled by VM_PFNMAP in VM_NO_THP bit-mask.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Pallipadi Venkatesh <venkatesh.pallipadi@intel.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Ingo Molnar <mingo@redhat.com>
---
arch/x86/mm/pat.c | 25 +++++++++++++++++--------
include/asm-generic/pgtable.h | 4 ++--
include/linux/mm.h | 15 +--------------
mm/huge_memory.c | 7 +++----
mm/memory.c | 15 ++++++++-------
5 files changed, 31 insertions(+), 35 deletions(-)
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index f6ff57b..5c8eb19 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -665,7 +665,7 @@ int track_pfn_vma_copy(struct vm_area_struct *vma)
unsigned long vma_size = vma->vm_end - vma->vm_start;
pgprot_t pgprot;

- if (is_linear_pfn_mapping(vma)) {
+ if (vma->vm_flags & VM_PAT) {
/*
* reserve the whole chunk covered by vma. We need the
* starting address and protection from pte.
@@ -690,16 +690,26 @@ int track_pfn_vma_copy(struct vm_area_struct *vma)
* single reserve_pfn_range call.
*/
int track_pfn_vma_new(struct vm_area_struct *vma, pgprot_t *prot,
- unsigned long pfn, unsigned long size)
+ unsigned long pfn, unsigned long addr, unsigned long size)
{
unsigned long flags;
resource_size_t paddr;
unsigned long vma_size = vma->vm_end - vma->vm_start;
+ int ret;

- if (is_linear_pfn_mapping(vma)) {
- /* reserve the whole chunk starting from vm_pgoff */
- paddr = (resource_size_t)vma->vm_pgoff << PAGE_SHIFT;
- return reserve_pfn_range(paddr, vma_size, prot, 0);
+ if (addr == vma->vm_start && size == vma_size) {
+ /* reserve the whole chunk starting from pfn */
+ paddr = (resource_size_t)pfn << PAGE_SHIFT;
+ ret = reserve_pfn_range(paddr, vma_size, prot, 0);
+ if (!ret) {
+ vma->vm_flags |= VM_PAT;
+ /*
+ * Save starting pfn in vm_pgoff for untrack_pfn_vma(),
+ * remap_pfn_range() do this only for cow-mappings.
+ */
+ vma->vm_pgoff = pfn;
+ }
+ return ret;
}

if (!pat_enabled)
@@ -724,11 +734,10 @@ void untrack_pfn_vma(struct vm_area_struct *vma, unsigned long pfn,
resource_size_t paddr;
unsigned long vma_size = vma->vm_end - vma->vm_start;

- if (is_linear_pfn_mapping(vma)) {
+ if (vma->vm_flags & VM_PAT) {
/* free the whole chunk starting from vm_pgoff */
paddr = (resource_size_t)vma->vm_pgoff << PAGE_SHIFT;
free_pfn_range(paddr, vma_size);
- return;
}
}

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 125c54e..688a2a5 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -389,7 +389,7 @@ static inline void ptep_modify_prot_commit(struct mm_struct *mm,
* for physical range indicated by pfn and size.
*/
static inline int track_pfn_vma_new(struct vm_area_struct *vma, pgprot_t *prot,
- unsigned long pfn, unsigned long size)
+ unsigned long pfn, unsigned long addr, unsigned long size)
{
return 0;
}
@@ -420,7 +420,7 @@ static inline void untrack_pfn_vma(struct vm_area_struct *vma,
}
#else
extern int track_pfn_vma_new(struct vm_area_struct *vma, pgprot_t *prot,
- unsigned long pfn, unsigned long size);
+ unsigned long pfn, unsigned long addr, unsigned long size);
extern int track_pfn_vma_copy(struct vm_area_struct *vma);
extern void untrack_pfn_vma(struct vm_area_struct *vma, unsigned long pfn,
unsigned long size);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index d8738a4..b8e5fe5 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -117,7 +117,7 @@ extern unsigned int kobjsize(const void *objp);
#define VM_CAN_NONLINEAR 0x08000000 /* Has ->fault & does nonlinear pages */
#define VM_MIXEDMAP 0x10000000 /* Can contain "struct page" and pure PFN pages */
#define VM_SAO 0x20000000 /* Strong Access Ordering (powerpc) */
-#define VM_PFN_AT_MMAP 0x40000000 /* PFNMAP vma that is fully mapped at mmap time */
+#define VM_PAT 0x40000000 /* PAT reserves whole VMA at once (x86) */
#define VM_MERGEABLE 0x80000000 /* KSM may merge identical pages */

/* Bits set in the VMA until the stack is in its final location */
@@ -158,19 +158,6 @@ extern pgprot_t protection_map[16];
#define FAULT_FLAG_RETRY_NOWAIT 0x10 /* Don't drop mmap_sem and wait when retrying */
#define FAULT_FLAG_KILLABLE 0x20 /* The fault task is in SIGKILL killable region */

-/*
- * This interface is used by x86 PAT code to identify a pfn mapping that is
- * linear over entire vma. This is to optimize PAT code that deals with
- * marking the physical region with a particular prot. This is not for generic
- * mm use. Note also that this check will not work if the pfn mapping is
- * linear for a vma starting at physical address 0. In which case PAT code
- * falls back to slow path of reserving physical range page by page.
- */
-static inline int is_linear_pfn_mapping(struct vm_area_struct *vma)
-{
- return !!(vma->vm_flags & VM_PFN_AT_MMAP);
-}
-
static inline int is_pfn_mapping(struct vm_area_struct *vma)
{
return !!(vma->vm_flags & VM_PFNMAP);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f0e5306..cf827da 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1650,7 +1650,7 @@ int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
* If is_pfn_mapping() is true is_learn_pfn_mapping() must be
* true too, verify it here.
*/
- VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
+ VM_BUG_ON(vma->vm_flags & VM_NO_THP);
hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
hend = vma->vm_end & HPAGE_PMD_MASK;
if (hstart < hend)
@@ -1908,7 +1908,7 @@ static void collapse_huge_page(struct mm_struct *mm,
* If is_pfn_mapping() is true is_learn_pfn_mapping() must be
* true too, verify it here.
*/
- VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
+ VM_BUG_ON(vma->vm_flags & VM_NO_THP);

pgd = pgd_offset(mm, address);
if (!pgd_present(*pgd))
@@ -2150,8 +2150,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
* If is_pfn_mapping() is true is_learn_pfn_mapping()
* must be true too, verify it here.
*/
- VM_BUG_ON(is_linear_pfn_mapping(vma) ||
- vma->vm_flags & VM_NO_THP);
+ VM_BUG_ON(vma->vm_flags & VM_NO_THP);

hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
hend = vma->vm_end & HPAGE_PMD_MASK;
diff --git a/mm/memory.c b/mm/memory.c
index 6105f47..e6e4dfd 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2145,7 +2145,7 @@ int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,

if (addr < vma->vm_start || addr >= vma->vm_end)
return -EFAULT;
- if (track_pfn_vma_new(vma, &pgprot, pfn, PAGE_SIZE))
+ if (track_pfn_vma_new(vma, &pgprot, pfn, addr, PAGE_SIZE))
return -EINVAL;

ret = insert_pfn(vma, addr, pfn, pgprot);
@@ -2285,23 +2285,24 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
* There's a horrible special case to handle copy-on-write
* behaviour that some programs depend on. We mark the "original"
* un-COW'ed pages by matching them up with "vma->vm_pgoff".
+ * See vm_normal_page() for details.
*/
- if (addr == vma->vm_start && end == vma->vm_end) {
+
+ if (is_cow_mapping(vma->vm_flags)) {
+ if (addr != vma->vm_start || end != vma->vm_end)
+ return -EINVAL;
vma->vm_pgoff = pfn;
- vma->vm_flags |= VM_PFN_AT_MMAP;
- } else if (is_cow_mapping(vma->vm_flags))
- return -EINVAL;
+ }

vma->vm_flags |= VM_IO | VM_RESERVED | VM_PFNMAP;

- err = track_pfn_vma_new(vma, &prot, pfn, PAGE_ALIGN(size));
+ err = track_pfn_vma_new(vma, &prot, pfn, addr, PAGE_ALIGN(size));
if (err) {
/*
* To indicate that track_pfn related cleanup is not
* needed from higher level routine calling unmap_vmas
*/
vma->vm_flags &= ~(VM_IO | VM_RESERVED | VM_PFNMAP);
- vma->vm_flags &= ~VM_PFN_AT_MMAP;
return -EINVAL;
}



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