Commit fa9949da authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

mm: use __SetPageSwapBacked and dont ClearPageSwapBacked 



v3.16 commit 07a42788 ("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: default avatarHugh Dickins <hughd@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Yang Shi <yang.shi@linaro.org>
Cc: Ning Qu <quning@gmail.com>
Reviewed-by: default avatarMel Gorman <mgorman@techsingularity.net>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9d5e6a9f

mm/migrate.c

+3 −3
Original line number Diff line number Diff line
@@ -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;

mm/rmap.c

+1 −1
Original line number Diff line number Diff line
@@ -1249,7 +1249,7 @@ void page_add_new_anon_rmap(struct page *page, 
	int nr = compound ? hpage_nr_pages(page) : 1;



	VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);

	SetPageSwapBacked(page);

	__SetPageSwapBacked(page);

	if (compound) {

		VM_BUG_ON_PAGE(!PageTransHuge(page), page);

		/* increment count (starts at -1) */

mm/shmem.c

+2 −2
Original line number Diff line number Diff line
@@ -1085,8 +1085,8 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp, 
	flush_dcache_page(newpage);



	__SetPageLocked(newpage);

	__SetPageSwapBacked(newpage);

	SetPageUptodate(newpage);

	SetPageSwapBacked(newpage);

	set_page_private(newpage, swap_index);

	SetPageSwapCache(newpage);
@@ -1276,8 +1276,8 @@ repeat: 
			goto decused;

		}



		__SetPageSwapBacked(page);

		__SetPageLocked(page);

		__SetPageSwapBacked(page);

		if (sgp == SGP_WRITE)

			__SetPageReferenced(page);

mm/swap_state.c

+1 −2
Original line number Diff line number Diff line
@@ -358,7 +358,7 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, 


		/* May fail (-ENOMEM) if radix-tree node allocation failed. */

		__SetPageLocked(new_page);

		SetPageSwapBacked(new_page);

		__SetPageSwapBacked(new_page);

		err = __add_to_swap_cache(new_page, entry);

		if (likely(!err)) {

			radix_tree_preload_end();
@@ -370,7 +370,6 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, 
			return new_page;

		}

		radix_tree_preload_end();

		ClearPageSwapBacked(new_page);

		__ClearPageLocked(new_page);

		/*

		 * add_to_swap_cache() doesn't return -EEXIST, so we can safely

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