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authorHugh Dickins <hughd@google.com>2013-02-22 16:35:13 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2013-02-23 17:50:19 -0800
commitb79bc0a0c79e06cc87e17530e9c1c56c6f297e17 (patch)
tree617d8e3b2d8be512373c3351a92630c28248ecee /mm/migrate.c
parentksm: make !merge_across_nodes migration safe (diff)
downloadlinux-dev-b79bc0a0c79e06cc87e17530e9c1c56c6f297e17.tar.xz
linux-dev-b79bc0a0c79e06cc87e17530e9c1c56c6f297e17.zip
ksm: enable KSM page migration
Migration of KSM pages is now safe: remove the PageKsm restrictions from mempolicy.c and migrate.c. But keep PageKsm out of __unmap_and_move()'s anon_vma contortions, which are irrelevant to KSM: it looks as if that code was preventing hotremove migration of KSM pages, unless they happened to be in swapcache. There is some question as to whether enforcing a NUMA mempolicy migration ought to migrate KSM pages, mapped into entirely unrelated processes; but moving page_mapcount > 1 is only permitted with MPOL_MF_MOVE_ALL anyway, and it seems reasonable to assume that you wouldn't set MADV_MERGEABLE on any area where this is a worry. Signed-off-by: Hugh Dickins <hughd@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Petr Holasek <pholasek@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Izik Eidus <izik.eidus@ravellosystems.com> Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to '')
-rw-r--r--mm/migrate.c21
1 files changed, 3 insertions, 18 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index e545ce7ddc17..20a03eb0667f 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -731,20 +731,6 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
lock_page(page);
}
- /*
- * Only memory hotplug's offline_pages() caller has locked out KSM,
- * and can safely migrate a KSM page. The other cases have skipped
- * PageKsm along with PageReserved - but it is only now when we have
- * the page lock that we can be certain it will not go KSM beneath us
- * (KSM will not upgrade a page from PageAnon to PageKsm when it sees
- * its pagecount raised, but only here do we take the page lock which
- * serializes that).
- */
- if (PageKsm(page) && !offlining) {
- rc = -EBUSY;
- goto unlock;
- }
-
/* charge against new page */
mem_cgroup_prepare_migration(page, newpage, &mem);
@@ -771,7 +757,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
* File Caches may use write_page() or lock_page() in migration, then,
* just care Anon page here.
*/
- if (PageAnon(page)) {
+ if (PageAnon(page) && !PageKsm(page)) {
/*
* Only page_lock_anon_vma_read() understands the subtleties of
* getting a hold on an anon_vma from outside one of its mms.
@@ -851,7 +837,6 @@ uncharge:
mem_cgroup_end_migration(mem, page, newpage,
(rc == MIGRATEPAGE_SUCCESS ||
rc == MIGRATEPAGE_BALLOON_SUCCESS));
-unlock:
unlock_page(page);
out:
return rc;
@@ -1155,7 +1140,7 @@ static int do_move_page_to_node_array(struct mm_struct *mm,
goto set_status;
/* Use PageReserved to check for zero page */
- if (PageReserved(page) || PageKsm(page))
+ if (PageReserved(page))
goto put_and_set;
pp->page = page;
@@ -1317,7 +1302,7 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
err = -ENOENT;
/* Use PageReserved to check for zero page */
- if (!page || PageReserved(page) || PageKsm(page))
+ if (!page || PageReserved(page))
goto set_status;
err = page_to_nid(page);