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. And remove the ClearPageSwapBacked from
read_swap_cache_async()'s and zswap_get_swap_cache_page()'s error
paths: it's not an error to free a page with PG_swapbacked set.
(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 <hu...@google.com>
---
mm/migrate.c | 6 +++---
mm/rmap.c | 2 +-
mm/shmem.c | 4 ++--
mm/swap_state.c | 3 +--
mm/zswap.c | 3 +--
5 files changed, 8 insertions(+), 10 deletions(-)
--- thpfs.orig/mm/migrate.c 2015-02-08 18:54:22.000000000 -0800
+++ thpfs/mm/migrate.c 2015-02-20 19:33:35.676074594 -0800
@@ -763,7 +763,7 @@ static int move_to_new_page(struct page
newpage->index = page->index;
newpage->mapping = page->mapping;
if (PageSwapBacked(page))
- SetPageSwapBacked(newpage);
+ __SetPageSwapBacked(newpage);
mapping = page_mapping(page);
if (!mapping)
@@ -978,7 +978,7 @@ out:
* during isolation.
*/
if (rc != MIGRATEPAGE_SUCCESS && put_new_page) {
- ClearPageSwapBacked(newpage);
+ __ClearPageSwapBacked(newpage);
put_new_page(newpage, private);
} else if (unlikely(__is_movable_balloon_page(newpage))) {
/* drop our reference, page already in the balloon */
@@ -1792,7 +1792,7 @@ int migrate_misplaced_transhuge_page(str
/* Prepare a page as a migration target */
__set_page_locked(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;
--- thpfs.orig/mm/rmap.c 2015-02-08 18:54:22.000000000 -0800
+++ thpfs/mm/rmap.c 2015-02-20 19:33:35.676074594 -0800
@@ -1068,7 +1068,7 @@ void page_add_new_anon_rmap(struct page
struct vm_area_struct *vma, unsigned long address)
{
VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
- SetPageSwapBacked(page);
+ __SetPageSwapBacked(page);
atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */
if (PageTransHuge(page))
__inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
--- thpfs.orig/mm/shmem.c 2015-02-08 18:54:22.000000000 -0800
+++ thpfs/mm/shmem.c 2015-02-20 19:33:35.676074594 -0800
@@ -987,8 +987,8 @@ static int shmem_replace_page(struct pag
flush_dcache_page(newpage);
__set_page_locked(newpage);
+ __SetPageSwapBacked(newpage);
SetPageUptodate(newpage);
- SetPageSwapBacked(newpage);
set_page_private(newpage, swap_index);
SetPageSwapCache(newpage);
@@ -1177,8 +1177,8 @@ repeat:
goto decused;
}
- __SetPageSwapBacked(page);
__set_page_locked(page);
+ __SetPageSwapBacked(page);
if (sgp == SGP_WRITE)
__SetPageReferenced(page);
--- thpfs.orig/mm/swap_state.c 2015-02-08 18:54:22.000000000 -0800
+++ thpfs/mm/swap_state.c 2015-02-20 19:33:35.676074594 -0800
@@ -364,7 +364,7 @@ struct page *read_swap_cache_async(swp_e
/* May fail (-ENOMEM) if radix-tree node allocation failed. */
__set_page_locked(new_page);
- SetPageSwapBacked(new_page);
+ __SetPageSwapBacked(new_page);
err = __add_to_swap_cache(new_page, entry);
if (likely(!err)) {
radix_tree_preload_end();
@@ -376,7 +376,6 @@ struct page *read_swap_cache_async(swp_e
return new_page;
}
radix_tree_preload_end();
- ClearPageSwapBacked(new_page);
__clear_page_locked(new_page);
/*
* add_to_swap_cache() doesn't return -EEXIST, so we can safely
--- thpfs.orig/mm/zswap.c 2015-02-08 18:54:22.000000000 -0800
+++ thpfs/mm/zswap.c 2015-02-20 19:33:35.676074594 -0800
@@ -491,7 +491,7 @@ static int zswap_get_swap_cache_page(swp
/* May fail (-ENOMEM) if radix-tree node allocation failed. */
__set_page_locked(new_page);
- SetPageSwapBacked(new_page);
+ __SetPageSwapBacked(new_page);
err = __add_to_swap_cache(new_page, entry);
if (likely(!err)) {
radix_tree_preload_end();
@@ -500,7 +500,6 @@ static int zswap_get_swap_cache_page(swp
return ZSWAP_SWAPCACHE_NEW;
}
radix_tree_preload_end();
- ClearPageSwapBacked(new_page);
__clear_page_locked(new_page);
/*
* add_to_swap_cache() doesn't return -EEXIST, so we can safely
--
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