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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2016-01-15 16:53:03 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-01-15 17:56:32 -0800
commitf765f540598a129dc4bb6f698fd4acc92f296c14 (patch)
treec7d11ce64f3849985a56412ffd543f0d419d2deb
parent14d27abd1d12a64c89df1ce8c00ef1403226db5a (diff)
ksm: prepare to new THP semantics
We don't need special code to stabilize THP. If you've got reference to any subpage of THP it will not be split under you. New split_huge_page() also accepts tail pages: no need in special code to get reference to head page. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Tested-by: Sasha Levin <sasha.levin@oracle.com> Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Jerome Marchand <jmarchan@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Steve Capper <steve.capper@linaro.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/ksm.c57
1 files changed, 10 insertions, 47 deletions
diff --git a/mm/ksm.c b/mm/ksm.c
index b4f7b69efad0..80c29b1b2b8a 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -441,20 +441,6 @@ static void break_cow(struct rmap_item *rmap_item)
up_read(&mm->mmap_sem);
}
-static struct page *page_trans_compound_anon(struct page *page)
-{
- if (PageTransCompound(page)) {
- struct page *head = compound_head(page);
- /*
- * head may actually be splitted and freed from under
- * us but it's ok here.
- */
- if (PageAnon(head))
- return head;
- }
- return NULL;
-}
-
static struct page *get_mergeable_page(struct rmap_item *rmap_item)
{
struct mm_struct *mm = rmap_item->mm;
@@ -470,7 +456,7 @@ static struct page *get_mergeable_page(struct rmap_item *rmap_item)
page = follow_page(vma, addr, FOLL_GET);
if (IS_ERR_OR_NULL(page))
goto out;
- if (PageAnon(page) || page_trans_compound_anon(page)) {
+ if (PageAnon(page)) {
flush_anon_page(vma, page, addr);
flush_dcache_page(page);
} else {
@@ -975,33 +961,6 @@ out:
return err;
}
-static int page_trans_compound_anon_split(struct page *page)
-{
- int ret = 0;
- struct page *transhuge_head = page_trans_compound_anon(page);
- if (transhuge_head) {
- /* Get the reference on the head to split it. */
- if (get_page_unless_zero(transhuge_head)) {
- /*
- * Recheck we got the reference while the head
- * was still anonymous.
- */
- if (PageAnon(transhuge_head))
- ret = split_huge_page(transhuge_head);
- else
- /*
- * Retry later if split_huge_page run
- * from under us.
- */
- ret = 1;
- put_page(transhuge_head);
- } else
- /* Retry later if split_huge_page run from under us. */
- ret = 1;
- }
- return ret;
-}
-
/*
* try_to_merge_one_page - take two pages and merge them into one
* @vma: the vma that holds the pte pointing to page
@@ -1020,9 +979,6 @@ static int try_to_merge_one_page(struct vm_area_struct *vma,
if (page == kpage) /* ksm page forked */
return 0;
- if (PageTransCompound(page) && page_trans_compound_anon_split(page))
- goto out;
- BUG_ON(PageTransCompound(page));
if (!PageAnon(page))
goto out;
@@ -1035,6 +991,13 @@ static int try_to_merge_one_page(struct vm_area_struct *vma,
*/
if (!trylock_page(page))
goto out;
+
+ if (PageTransCompound(page)) {
+ err = split_huge_page(page);
+ if (err)
+ goto out_unlock;
+ }
+
/*
* If this anonymous page is mapped only here, its pte may need
* to be write-protected. If it's mapped elsewhere, all of its
@@ -1065,6 +1028,7 @@ static int try_to_merge_one_page(struct vm_area_struct *vma,
}
}
+out_unlock:
unlock_page(page);
out:
return err;
@@ -1635,8 +1599,7 @@ next_mm:
cond_resched();
continue;
}
- if (PageAnon(*page) ||
- page_trans_compound_anon(*page)) {
+ if (PageAnon(*page)) {
flush_anon_page(vma, *page, ksm_scan.address);
flush_dcache_page(*page);
rmap_item = get_next_rmap_item(slot,