mm/debug.c: PageAnon() is true for PageKsm() pages

PageAnon() and PageKsm() use the low two bits of the page->mapping
pointer to indicate the page type.  PageAnon() only checks the LSB while
PageKsm() checks the least significant 2 bits are equal to 3.

Therefore, PageAnon() is true for KSM pages.  __dump_page() incorrectly
will never print "ksm" because it checks PageAnon() first.  Fix this by
checking PageKsm() first.

Link: http://lkml.kernel.org/r/20191113000651.20677-1-rcampbell@nvidia.com
Fixes: 1c6fb1d89e73 ("mm: print more information about mapping in __dump_page")
Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/debug.c b/mm/debug.c
index 772d4cf..0461df1 100644 (file)
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -77,10 +77,10 @@ void __dump_page(struct page *page, const char *reason)
                pr_warn("page:%px refcount:%d mapcount:%d mapping:%px index:%#lx\n",
                        page, page_ref_count(page), mapcount,
                        page->mapping, page_to_pgoff(page));
-       if (PageAnon(page))
-               pr_warn("anon flags: %#lx(%pGp)\n", page->flags, &page->flags);
-       else if (PageKsm(page))
+       if (PageKsm(page))
                pr_warn("ksm flags: %#lx(%pGp)\n", page->flags, &page->flags);
+       else if (PageAnon(page))
+               pr_warn("anon flags: %#lx(%pGp)\n", page->flags, &page->flags);
        else if (mapping) {
                if (mapping->host && mapping->host->i_dentry.first) {
                        struct dentry *dentry;