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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2016-10-07 17:01:40 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-10-07 18:46:29 -0700
commit9996f05eac09815121bb718249f21914a667791f (patch)
tree5895100f41462c5aa2c68a8b992ba2f2845b134b /mm
parent8f26e0b176f3484c49d55d88fe6083a9cf9ff443 (diff)
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mm: clarify why we avoid page_mapcount() for slab pages in dump_page()
Let's add comment on why we skip page_mapcount() for sl[aou]b pages. Link: http://lkml.kernel.org/r/20160922105532.GB24593@node Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/debug.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/mm/debug.c b/mm/debug.c
index 74c7cae4f683..9feb699c5d25 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -42,6 +42,11 @@ const struct trace_print_flags vmaflag_names[] = {
void __dump_page(struct page *page, const char *reason)
{
+ /*
+ * Avoid VM_BUG_ON() in page_mapcount().
+ * page->_mapcount space in struct page is used by sl[aou]b pages to
+ * encode own info.
+ */
int mapcount = PageSlab(page) ? 0 : page_mapcount(page);
pr_emerg("page:%p count:%d mapcount:%d mapping:%p index:%#lx",