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>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index ba86ddaa2bb80f396d52884183de530dc0887b85..bc0ad24cf8c0d85cc0e9a8283c4ebf4c2be4f41a 100644 (file)
--- 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 c5e88bcd8ec389c93cd64be220419f69ec44923f..bbab1e37055e22df235af61ddd201fe4b9832283 100644 (file)
--- 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