Eric Lee / smarc-ti-linux-kernel

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Commit b79bc0a0c79e06cc87e17530e9c1c56c6f297e17

Authored by Hugh Dickins
Committed by Linus Torvalds
1 parent 4146d2d673
Exists in master and in 20 other branches dlt-processor-sdk-linux-03.00.00.04, newt-ti-linux-3.12.y, processor-sdk-linux-01.00.00, processor-sdk-linux-02.00.01, smarc-ti-linux-3.12.10, smarc-ti-linux-3.12.y, smarc-ti-linux-3.14.y, smarc-ti-linux-3.15.y, smarc-ti-lsk-linux-4.1.y, smarct3x-processor-sdk-04.01.00.06, smarct3x-processor-sdk-linux-02.00.01, smarct3x-processor-sdk-linux-03.00.00.04, smarct4x-800-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-04.01.00.06, smarct4x-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-linux-03.00.00.04, ti-linux-3.12.y, ti-linux-3.14.y, ti-linux-3.15.y, ti-lsk-linux-4.1.y

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>

Showing 2 changed files with 4 additions and 20 deletions Side-by-side Diff

... ... @@ -496,9 +496,8 @@
496 496 /*
497 497 * vm_normal_page() filters out zero pages, but there might
498 498 * still be PageReserved pages to skip, perhaps in a VDSO.
499   - * And we cannot move PageKsm pages sensibly or safely yet.
500 499 */
501   - if (PageReserved(page) || PageKsm(page))
  500 + if (PageReserved(page))
502 501 continue;
503 502 nid = page_to_nid(page);
504 503 if (node_isset(nid, *nodes) == !!(flags & MPOL_MF_INVERT))
... ... @@ -731,20 +731,6 @@
731 731 lock_page(page);
732 732 }
733 733  
734   - /*
735   - * Only memory hotplug's offline_pages() caller has locked out KSM,
736   - * and can safely migrate a KSM page. The other cases have skipped
737   - * PageKsm along with PageReserved - but it is only now when we have
738   - * the page lock that we can be certain it will not go KSM beneath us
739   - * (KSM will not upgrade a page from PageAnon to PageKsm when it sees
740   - * its pagecount raised, but only here do we take the page lock which
741   - * serializes that).
742   - */
743   - if (PageKsm(page) && !offlining) {
744   - rc = -EBUSY;
745   - goto unlock;
746   - }
747   -
748 734 /* charge against new page */
749 735 mem_cgroup_prepare_migration(page, newpage, &mem);
750 736  
... ... @@ -771,7 +757,7 @@
771 757 * File Caches may use write_page() or lock_page() in migration, then,
772 758 * just care Anon page here.
773 759 */
774   - if (PageAnon(page)) {
  760 + if (PageAnon(page) && !PageKsm(page)) {
775 761 /*
776 762 * Only page_lock_anon_vma_read() understands the subtleties of
777 763 * getting a hold on an anon_vma from outside one of its mms.
... ... @@ -851,7 +837,6 @@
851 837 mem_cgroup_end_migration(mem, page, newpage,
852 838 (rc == MIGRATEPAGE_SUCCESS ||
853 839 rc == MIGRATEPAGE_BALLOON_SUCCESS));
854   -unlock:
855 840 unlock_page(page);
856 841 out:
857 842 return rc;
... ... @@ -1155,7 +1140,7 @@
1155 1140 goto set_status;
1156 1141  
1157 1142 /* Use PageReserved to check for zero page */
1158   - if (PageReserved(page) || PageKsm(page))
  1143 + if (PageReserved(page))
1159 1144 goto put_and_set;
1160 1145  
1161 1146 pp->page = page;
... ... @@ -1317,7 +1302,7 @@
1317 1302  
1318 1303 err = -ENOENT;
1319 1304 /* Use PageReserved to check for zero page */
1320   - if (!page || PageReserved(page) || PageKsm(page))
  1305 + if (!page || PageReserved(page))
1321 1306 goto set_status;
1322 1307  
1323 1308 err = page_to_nid(page);