[PATCH] Direct Migration V9: migrate_pages() extension

Add direct migration support with fall back to swap.

Direct migration support on top of the swap based page migration facility.

This allows the direct migration of anonymous pages and the migration of file
backed pages by dropping the associated buffers (requires writeout).

Fall back to swap out if necessary.

The patch is based on lots of patches from the hotplug project but the code
was restructured, documented and simplified as much as possible.

Note that an additional patch that defines the migrate_page() method for
filesystems is necessary in order to avoid writeback for anonymous and file
backed pages.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Mike Kravetz <kravetz@us.ibm.com>
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 12 insertions, 9 deletions

diff --git a/mm/rmap.c b/mm/rmap.c
index d85a99d28c03..13fad5fcdf79 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -52,6 +52,7 @@
 #include <linux/init.h>
 #include <linux/rmap.h>
 #include <linux/rcupdate.h>
+#include <linux/module.h>
 
 #include <asm/tlbflush.h>
 
@@ -541,7 +542,8 @@ void page_remove_rmap(struct page *page)
  * Subfunctions of try_to_unmap: try_to_unmap_one called
  * repeatedly from either try_to_unmap_anon or try_to_unmap_file.
  */
-static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma)
+static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
+                                int ignore_refs)
 {
         struct mm_struct *mm = vma->vm_mm;
         unsigned long address;
@@ -564,7 +566,8 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma)
          * skipped over this mm) then we should reactivate it.
          */
         if ((vma->vm_flags & VM_LOCKED) ||
-                        ptep_clear_flush_young(vma, address, pte)) {
+                        (ptep_clear_flush_young(vma, address, pte)
+                                && !ignore_refs)) {
                 ret = SWAP_FAIL;
                 goto out_unmap;
         }
@@ -698,7 +701,7 @@ static void try_to_unmap_cluster(unsigned long cursor,
         pte_unmap_unlock(pte - 1, ptl);
 }
 
-static int try_to_unmap_anon(struct page *page)
+static int try_to_unmap_anon(struct page *page, int ignore_refs)
 {
         struct anon_vma *anon_vma;
         struct vm_area_struct *vma;
@@ -709,7 +712,7 @@ static int try_to_unmap_anon(struct page *page)
                 return ret;
 
         list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
-                ret = try_to_unmap_one(page, vma);
+                ret = try_to_unmap_one(page, vma, ignore_refs);
                 if (ret == SWAP_FAIL || !page_mapped(page))
                         break;
         }
@@ -726,7 +729,7 @@ static int try_to_unmap_anon(struct page *page)
  *
  * This function is only called from try_to_unmap for object-based pages.
  */
-static int try_to_unmap_file(struct page *page)
+static int try_to_unmap_file(struct page *page, int ignore_refs)
 {
         struct address_space *mapping = page->mapping;
         pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
@@ -740,7 +743,7 @@ static int try_to_unmap_file(struct page *page)
 
         spin_lock(&mapping->i_mmap_lock);
         vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
-                ret = try_to_unmap_one(page, vma);
+                ret = try_to_unmap_one(page, vma, ignore_refs);
                 if (ret == SWAP_FAIL || !page_mapped(page))
                         goto out;
         }
@@ -825,16 +828,16 @@ out:
  * SWAP_AGAIN   - we missed a mapping, try again later
  * SWAP_FAIL    - the page is unswappable
  */
-int try_to_unmap(struct page *page)
+int try_to_unmap(struct page *page, int ignore_refs)
 {
         int ret;
 
         BUG_ON(!PageLocked(page));
 
         if (PageAnon(page))
-                ret = try_to_unmap_anon(page);
+                ret = try_to_unmap_anon(page, ignore_refs);
         else
-                ret = try_to_unmap_file(page);
+                ret = try_to_unmap_file(page, ignore_refs);
 
         if (!page_mapped(page))
                 ret = SWAP_SUCCESS;