From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm: use __SetPageSwapBacked and dont ClearPageSwapBacked
v3.16 commit 07a427884348 ("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 <hughd@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Andres Lagar-Cavilla <andreslc@xxxxxxxxxx>
Cc: Yang Shi <yang.shi@xxxxxxxxxx>
Cc: Ning Qu <quning@xxxxxxxxx>
Reviewed-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/migrate.c | 6 +++---
mm/rmap.c | 2 +-
mm/shmem.c | 4 ++--
mm/swap_state.c | 3 +--
4 files changed, 7 insertions(+), 8 deletions(-)
diff -puN mm/migrate.c~mm-use-__setpageswapbacked-and-dont-clearpageswapbacked mm/migrate.c
--- a/mm/migrate.c~mm-use-__setpageswapbacked-and-dont-clearpageswapbacked
+++ a/mm/migrate.c
@@ -332,7 +332,7 @@ int migrate_page_move_mapping(struct add
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 add
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(str
/* 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;
diff -puN mm/rmap.c~mm-use-__setpageswapbacked-and-dont-clearpageswapbacked mm/rmap.c
--- a/mm/rmap.c~mm-use-__setpageswapbacked-and-dont-clearpageswapbacked
+++ a/mm/rmap.c
@@ -1249,7 +1249,7 @@ void page_add_new_anon_rmap(struct 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) */
diff -puN mm/shmem.c~mm-use-__setpageswapbacked-and-dont-clearpageswapbacked mm/shmem.c
--- a/mm/shmem.c~mm-use-__setpageswapbacked-and-dont-clearpageswapbacked
+++ a/mm/shmem.c
@@ -1085,8 +1085,8 @@ static int shmem_replace_page(struct pag
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);
diff -puN mm/swap_state.c~mm-use-__setpageswapbacked-and-dont-clearpageswapbacked mm/swap_state.c
--- a/mm/swap_state.c~mm-use-__setpageswapbacked-and-dont-clearpageswapbacked
+++ a/mm/swap_state.c
@@ -358,7 +358,7 @@ struct page *__read_swap_cache_async(swp
/* 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
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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