The function prep_new_page() sets almost everything in the struct page of the
page being allocated, except page->pfmemalloc. This is not obvious and has at
least once led to a bug where page->pfmemalloc was forgotten to be set
correctly, see commit 8fb74b9fb2b1 ("mm: compaction: partially revert capture
of suitable high-order page").
This patch moves the pfmemalloc setting to prep_new_page(), which means it
needs to gain alloc_flags parameter. The call to prep_new_page is moved from
buffered_rmqueue() to get_page_from_freelist(), which also leads to simpler
code. An obsolete comment for buffered_rmqueue() is replaced.
In addition to better maintainability there is a small reduction of code and
stack usage for get_page_from_freelist(), which inlines the other functions
involved.
add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-145 (-145)
function old new delta
get_page_from_freelist 2670 2525 -145
Stack usage is reduced from 184 to 168 bytes.
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
---
mm/page_alloc.c | 37 ++++++++++++++++---------------------
1 file changed, 16 insertions(+), 21 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1bb65e6..0c77a97 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -970,7 +970,8 @@ static inline int check_new_page(struct page *page)
return 0;
}
-static int prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags)
+static int prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,
+ int alloc_flags)
{
int i;
@@ -994,6 +995,14 @@ static int prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags)
set_page_owner(page, order, gfp_flags);
+ /*
+ * page->pfmemalloc is set when ALLOC_NO_WATERMARKS was necessary to
+ * allocate the page. The expectation is that the caller is taking
+ * steps that will free more memory. The caller should avoid the page
+ * being used for !PFMEMALLOC purposes.
+ */
+ page->pfmemalloc = !!(alloc_flags & ALLOC_NO_WATERMARKS);
+
return 0;
}
@@ -1642,9 +1651,7 @@ int split_free_page(struct page *page)
}
/*
- * Really, prep_compound_page() should be called from __rmqueue_bulk(). But
- * we cheat by calling it from here, in the order > 0 path. Saves a branch
- * or two.
+ * Allocate a page from the given zone. Use pcplists for order-0 allocations.
*/
static inline
struct page *buffered_rmqueue(struct zone *preferred_zone,
@@ -1655,7 +1662,6 @@ struct page *buffered_rmqueue(struct zone *preferred_zone,
struct page *page;
bool cold = ((gfp_flags & __GFP_COLD) != 0);
-again:
if (likely(order == 0)) {
struct per_cpu_pages *pcp;
struct list_head *list;
@@ -1711,8 +1717,6 @@ again:
local_irq_restore(flags);
VM_BUG_ON_PAGE(bad_range(zone, page), page);
- if (prep_new_page(page, order, gfp_flags))
- goto again;
return page;
failed:
@@ -2177,25 +2181,16 @@ zonelist_scan:
try_this_zone:
page = buffered_rmqueue(preferred_zone, zone, order,
gfp_mask, migratetype);
- if (page)
- break;
+ if (page) {
+ if (prep_new_page(page, order, gfp_mask, alloc_flags))
+ goto try_this_zone;
+ return page;
+ }
this_zone_full:
if (IS_ENABLED(CONFIG_NUMA) && zlc_active)
zlc_mark_zone_full(zonelist, z);
}
- if (page) {
- /*
- * page->pfmemalloc is set when ALLOC_NO_WATERMARKS was
- * necessary to allocate the page. The expectation is
- * that the caller is taking steps that will free more
- * memory. The caller should avoid the page being used
- * for !PFMEMALLOC purposes.
- */
- page->pfmemalloc = !!(alloc_flags & ALLOC_NO_WATERMARKS);
- return page;
- }
-
/*
* The first pass makes sure allocations are spread fairly within the
* local node. However, the local node might have free pages left
--
2.1.2
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