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authorAnthony Yznaga <anthony.yznaga@oracle.com>2018-12-28 00:37:31 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2018-12-28 12:11:50 -0800
commit144552ff8995dd34d049a203d636b259ab751137 (patch)
tree3e3ed4aa4afc2e22c12120be581e1846b864b4db
parentb6fb87b8e3ff1ef6bcf68470f24a97c984554d5a (diff)
downloadlinux-144552ff8995dd34d049a203d636b259ab751137.tar.bz2
/proc/kpagecount: return 0 for special pages that are never mapped
Certain pages that are never mapped to userspace have a type indicated in the page_type field of their struct pages (e.g. PG_buddy). page_type overlaps with _mapcount so set the count to 0 and avoid calling page_mapcount() for these pages. [anthony.yznaga@oracle.com: incorporate feedback from Matthew Wilcox] Link: http://lkml.kernel.org/r/1544481313-27318-1-git-send-email-anthony.yznaga@oracle.com Link: http://lkml.kernel.org/r/1543963526-27917-1-git-send-email-anthony.yznaga@oracle.com Signed-off-by: Anthony Yznaga <anthony.yznaga@oracle.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Matthew Wilcox <willy@infradead.org> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: David Rientjes <rientjes@google.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Miles Chen <miles.chen@mediatek.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/proc/page.c2
-rw-r--r--include/linux/page-flags.h6
2 files changed, 7 insertions, 1 deletions
diff --git a/fs/proc/page.c b/fs/proc/page.c
index 6c517b11acf8..40b05e0d4274 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -46,7 +46,7 @@ static ssize_t kpagecount_read(struct file *file, char __user *buf,
ppage = pfn_to_page(pfn);
else
ppage = NULL;
- if (!ppage || PageSlab(ppage))
+ if (!ppage || PageSlab(ppage) || page_has_type(ppage))
pcount = 0;
else
pcount = page_mapcount(ppage);
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 50ce1bddaf56..39b4494e29f1 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -669,6 +669,7 @@ PAGEFLAG_FALSE(DoubleMap)
#define PAGE_TYPE_BASE 0xf0000000
/* Reserve 0x0000007f to catch underflows of page_mapcount */
+#define PAGE_MAPCOUNT_RESERVE -128
#define PG_buddy 0x00000080
#define PG_balloon 0x00000100
#define PG_kmemcg 0x00000200
@@ -677,6 +678,11 @@ PAGEFLAG_FALSE(DoubleMap)
#define PageType(page, flag) \
((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE)
+static inline int page_has_type(struct page *page)
+{
+ return (int)page->page_type < PAGE_MAPCOUNT_RESERVE;
+}
+
#define PAGE_TYPE_OPS(uname, lname) \
static __always_inline int Page##uname(struct page *page) \
{ \