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mm: use __SetPageSwapBacked and dont ClearPageSwapBacked

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v3.16 commit 07a4278843 ("mm: shmem: avoid atomic operation during
shmem_getpage_gfp") rightly replaced one instance of SetPageSwapBacked
by __SetPageSwapBacked, pointing out that the newly allocated page is
not yet visible to other users (except speculative get_page_unless_zero-
ers, who may not update page flags before their further checks).

That was part of a series in which Mel was focused on tmpfs profiles:
but almost all SetPageSwapBacked uses can be so optimized, with the same
justification.

Remove ClearPageSwapBacked from __read_swap_cache_async() error path:
it's not an error to free a page with PG_swapbacked set.

Follow a convention of __SetPageLocked, __SetPageSwapBacked instead of
doing it differently in different places; but that's for tidiness - if
the ordering actually mattered, we should not be using the __variants.

There's probably scope for further __SetPageFlags in other places, but
SwapBacked is the one I'm interested in at the moment.

Signed-off-by: Hugh Dickins <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Andres Lagar-Cavilla <[email protected]>
Cc: Yang Shi <[email protected]>
Cc: Ning Qu <[email protected]>
Reviewed-by: Mel Gorman <[email protected]>
Cc: Konstantin Khlebnikov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Hugh Dickins 2016-05-19 17:12:41 -07:00 • committed by Linus Torvalds
commit fa9949da59
4 changed files with 7 additions and 8 deletions
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6
mm/migrate.c
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@ -332,7 +332,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
newpage->index = page->index;
newpage->mapping = page->mapping;
if (PageSwapBacked(page))
SetPageSwapBacked(newpage);
__SetPageSwapBacked(newpage);
return MIGRATEPAGE_SUCCESS;
}
@ -378,7 +378,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
newpage->index = page->index;
newpage->mapping = page->mapping;
if (PageSwapBacked(page))
SetPageSwapBacked(newpage);
__SetPageSwapBacked(newpage);
get_page(newpage); /* add cache reference */
if (PageSwapCache(page)) {
@ -1791,7 +1791,7 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
/* Prepare a page as a migration target */
__SetPageLocked(new_page);
SetPageSwapBacked(new_page);
__SetPageSwapBacked(new_page);
/* anon mapping, we can simply copy page->mapping to the new page: */
new_page->mapping = page->mapping;