mm, x86, pat: rework linear pfn-mmap tracking

Replace the 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.

[suresh.b.siddha@intel.com: Reset the VM_PAT flag as part of untrack_pfn_vma()]
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Venkatesh Pallipadi <venki@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Carsten Otte <cotte@de.ibm.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Eric Paris <eparis@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: James Morris <james.l.morris@oracle.com>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Kentaro Takeda <takedakn@nttdata.co.jp>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Robert Richter <robert.richter@amd.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Venkatesh Pallipadi <venki@google.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

5 files changed, 30 insertions, 58 deletions

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 74a702674e8..0eb572eda40 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -677,7 +677,7 @@ int track_pfn_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.
@@ -699,14 +699,20 @@ int track_pfn_copy(struct vm_area_struct *vma)
  * single reserve_pfn_range call.
  */
 int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot,
-                    unsigned long pfn, unsigned long size)
+                    unsigned long pfn, unsigned long addr, unsigned long size)
 {
         resource_size_t paddr = (resource_size_t)pfn << PAGE_SHIFT;
         unsigned long flags;
 
         /* reserve the whole chunk starting from paddr */
-        if (is_linear_pfn_mapping(vma))
-                return reserve_pfn_range(paddr, size, prot, 0);
+        if (addr == vma->vm_start && size == (vma->vm_end - vma->vm_start)) {
+                int ret;
+
+                ret = reserve_pfn_range(paddr, size, prot, 0);
+                if (!ret)
+                        vma->vm_flags |= VM_PAT;
+                return ret;
+        }
 
         if (!pat_enabled)
                 return 0;
@@ -758,7 +764,7 @@ void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
         resource_size_t paddr;
         unsigned long prot;
 
-        if (!is_linear_pfn_mapping(vma))
+        if (!(vma->vm_flags & VM_PAT))
                 return;
 
         /* free the chunk starting from pfn or the whole chunk */
@@ -772,6 +778,7 @@ void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
                 size = vma->vm_end - vma->vm_start;
         }
         free_pfn_range(paddr, size);
+        vma->vm_flags &= ~VM_PAT;
 }
 
 pgprot_t pgprot_writecombine(pgprot_t prot)
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index d4d4592c97f..c9a612069c8 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -391,7 +391,8 @@ static inline void ptep_modify_prot_commit(struct mm_struct *mm,
  * by remap_pfn_range() for physical range indicated by pfn and size.
  */
 static inline int track_pfn_remap(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;
 }
@@ -426,7 +427,8 @@ static inline void untrack_pfn(struct vm_area_struct *vma,
 }
 #else
 extern int track_pfn_remap(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_insert(struct vm_area_struct *vma, pgprot_t *prot,
                             unsigned long pfn);
 extern int track_pfn_copy(struct vm_area_struct *vma);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 311be906b57..75d1632d347 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 */
@@ -159,24 +159,6 @@ extern pgprot_t protection_map[16];
 #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);
-}
-
-/*
  * vm_fault is filled by the the pagefault handler and passed to the vma's
  * ->fault function. The vma's ->fault is responsible for returning a bitmask
  * of VM_FAULT_xxx flags that give details about how the fault was handled.
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 141dbb69509..73cb22ee966 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1655,11 +1655,7 @@ int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
         if (vma->vm_ops)
                 /* khugepaged not yet working on file or special mappings */
                 return 0;
-        /*
-         * 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)
@@ -1912,11 +1908,7 @@ static void collapse_huge_page(struct mm_struct *mm,
                 goto out;
         if (is_vma_temporary_stack(vma))
                 goto out;
-        /*
-         * 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))
@@ -2154,12 +2146,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
                         goto skip;
                 if (is_vma_temporary_stack(vma))
                         goto skip;
-                /*
-                 * 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 6bef278ad30..655e1429388 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1055,7 +1055,7 @@ int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
         if (is_vm_hugetlb_page(vma))
                 return copy_hugetlb_page_range(dst_mm, src_mm, vma);
 
-        if (unlikely(is_pfn_mapping(vma))) {
+        if (unlikely(vma->vm_flags & VM_PFNMAP)) {
                 /*
                  * We do not free on error cases below as remove_vma
                  * gets called on error from higher level routine
@@ -1327,7 +1327,7 @@ static void unmap_single_vma(struct mmu_gather *tlb,
         if (vma->vm_file)
                 uprobe_munmap(vma, start, end);
 
-        if (unlikely(is_pfn_mapping(vma)))
+        if (unlikely(vma->vm_flags & VM_PFNMAP))
                 untrack_pfn(vma, 0, 0);
 
         if (start != end) {
@@ -2299,26 +2299,20 @@ 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))
+        }
+
+        err = track_pfn_remap(vma, &prot, pfn, addr, PAGE_ALIGN(size));
+        if (err)
                 return -EINVAL;
 
         vma->vm_flags |= VM_IO | VM_RESERVED | VM_PFNMAP;
 
-        err = track_pfn_remap(vma, &prot, pfn, 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;
-        }
-
         BUG_ON(addr >= end);
         pfn -= addr >> PAGE_SHIFT;
         pgd = pgd_offset(mm, addr);