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ksm: prepare to new THP semantics

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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>
This commit is contained in:
Kirill A. Shutemov 2016-01-15 16:53:03 -08:00 committed by Linus Torvalds
parent 14d27abd1d
commit f765f54059
1 changed files with 10 additions and 47 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

57
mm/ksm.c
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@ -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,