mm: add vm_insert_mixed

vm_insert_mixed will insert either a raw pfn or a refcounted struct page into
the page tables, depending on whether vm_normal_page() will return the page or
not.  With the introduction of the new pte bit, this is now a too tricky for
drivers to be doing themselves.

filemap_xip uses this in a subsequent patch.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Jared Hulbert <jaredeh@gmail.com>
Cc: Carsten Otte <cotte@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 62 insertions, 26 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index ba86ddaa2bb8..bc0ad24cf8c0 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1152,6 +1152,8 @@ int remap_pfn_range(struct vm_area_struct *, unsigned long addr,
 int vm_insert_page(struct vm_area_struct *, unsigned long addr, struct page *);
 int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
                         unsigned long pfn);
+int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
+                        unsigned long pfn);
 
 struct page *follow_page(struct vm_area_struct *, unsigned long address,
                         unsigned int foll_flags);
diff --git a/mm/memory.c b/mm/memory.c
index c5e88bcd8ec3..bbab1e37055e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1176,8 +1176,10 @@ pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr,
  * old drivers should use this, and they needed to mark their
  * pages reserved for the old functions anyway.
  */
-static int insert_page(struct mm_struct *mm, unsigned long addr, struct page *page, pgprot_t prot)
+static int insert_page(struct vm_area_struct *vma, unsigned long addr,
+                        struct page *page, pgprot_t prot)
 {
+        struct mm_struct *mm = vma->vm_mm;
         int retval;
         pte_t *pte;
         spinlock_t *ptl;
@@ -1237,17 +1239,46 @@ out:
  *
  * The page does not need to be reserved.
  */
-int vm_insert_page(struct vm_area_struct *vma, unsigned long addr, struct page *page)
+int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
+                        struct page *page)
 {
         if (addr < vma->vm_start || addr >= vma->vm_end)
                 return -EFAULT;
         if (!page_count(page))
                 return -EINVAL;
         vma->vm_flags |= VM_INSERTPAGE;
-        return insert_page(vma->vm_mm, addr, page, vma->vm_page_prot);
+        return insert_page(vma, addr, page, vma->vm_page_prot);
 }
 EXPORT_SYMBOL(vm_insert_page);
 
+static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
+                        unsigned long pfn, pgprot_t prot)
+{
+        struct mm_struct *mm = vma->vm_mm;
+        int retval;
+        pte_t *pte, entry;
+        spinlock_t *ptl;
+
+        retval = -ENOMEM;
+        pte = get_locked_pte(mm, addr, &ptl);
+        if (!pte)
+                goto out;
+        retval = -EBUSY;
+        if (!pte_none(*pte))
+                goto out_unlock;
+
+        /* Ok, finally just insert the thing.. */
+        entry = pte_mkspecial(pfn_pte(pfn, prot));
+        set_pte_at(mm, addr, pte, entry);
+        update_mmu_cache(vma, addr, entry); /* XXX: why not for insert_page? */
+
+        retval = 0;
+out_unlock:
+        pte_unmap_unlock(pte, ptl);
+out:
+        return retval;
+}
+
 /**
  * vm_insert_pfn - insert single pfn into user vma
  * @vma: user vma to map to
@@ -1261,13 +1292,8 @@ EXPORT_SYMBOL(vm_insert_page);
  * in that case the handler should return NULL.
  */
 int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
-                unsigned long pfn)
+                        unsigned long pfn)
 {
-        struct mm_struct *mm = vma->vm_mm;
-        int retval;
-        pte_t *pte, entry;
-        spinlock_t *ptl;
-
         /*
          * Technically, architectures with pte_special can avoid all these
          * restrictions (same for remap_pfn_range).  However we would like
@@ -1280,27 +1306,35 @@ int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
         BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
 
-        retval = -ENOMEM;
-        pte = get_locked_pte(mm, addr, &ptl);
-        if (!pte)
-                goto out;
-        retval = -EBUSY;
-        if (!pte_none(*pte))
-                goto out_unlock;
+        if (addr < vma->vm_start || addr >= vma->vm_end)
+                return -EFAULT;
+        return insert_pfn(vma, addr, pfn, vma->vm_page_prot);
+}
+EXPORT_SYMBOL(vm_insert_pfn);
 
-        /* Ok, finally just insert the thing.. */
-        entry = pte_mkspecial(pfn_pte(pfn, vma->vm_page_prot));
-        set_pte_at(mm, addr, pte, entry);
-        update_mmu_cache(vma, addr, entry);
+int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
+                        unsigned long pfn)
+{
+        BUG_ON(!(vma->vm_flags & VM_MIXEDMAP));
 
-        retval = 0;
-out_unlock:
-        pte_unmap_unlock(pte, ptl);
+        if (addr < vma->vm_start || addr >= vma->vm_end)
+                return -EFAULT;
 
-out:
-        return retval;
+        /*
+         * If we don't have pte special, then we have to use the pfn_valid()
+         * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must*
+         * refcount the page if pfn_valid is true (hence insert_page rather
+         * than insert_pfn).
+         */
+        if (!HAVE_PTE_SPECIAL && pfn_valid(pfn)) {
+                struct page *page;
+
+                page = pfn_to_page(pfn);
+                return insert_page(vma, addr, page, vma->vm_page_prot);
+        }
+        return insert_pfn(vma, addr, pfn, vma->vm_page_prot);
 }
-EXPORT_SYMBOL(vm_insert_pfn);
+EXPORT_SYMBOL(vm_insert_mixed);
 
 /*
  * maps a range of physical memory into the requested pages. the old