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authorMichal Hocko <mhocko@suse.com>2018-12-28 00:38:36 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2018-12-28 12:11:51 -0800
commite0975b2aae0e669f995f7d5f11db25c3080ae11c (patch)
tree85ef72a9df87997d6b35f298a0cb5230da7f1552
parentbb8965bd82fd4ed433a888f1383016ab3fa0d7de (diff)
mm, fault_around: do not take a reference to a locked page
filemap_map_pages takes a speculative reference to each page in the range before it tries to lock that page. While this is correct it also can influence page migration which will bail out when seeing an elevated reference count. The faultaround code would bail on seeing a locked page so we can pro-actively check the PageLocked bit before page_cache_get_speculative and prevent from pointless reference count churn. Link: http://lkml.kernel.org/r/20181211142741.2607-4-mhocko@kernel.org Signed-off-by: Michal Hocko <mhocko@suse.com> Suggested-by: Jan Kara <jack@suse.cz> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reviewed-by: David Hildenbrand <david@redhat.com> Acked-by: Hugh Dickins <hughd@google.com> Reviewed-by: William Kucharski <william.kucharski@oracle.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/filemap.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index 8cec52968e83..29655fb47a2c 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2614,6 +2614,13 @@ void filemap_map_pages(struct vm_fault *vmf,
goto next;
head = compound_head(page);
+
+ /*
+ * Check for a locked page first, as a speculative
+ * reference may adversely influence page migration.
+ */
+ if (PageLocked(head))
+ goto next;
if (!page_cache_get_speculative(head))
goto next;