mm: improve dump_page() for compound pages (6197ab98) · Commits · 戴 / test

There was no protection against a corrupted struct page having an implausible compound_head(). Sanity check that a compound page has a head within reach of the maximum allocatable page (this will need to be adjusted if one of the plans to allocate 1GB pages comes to fruition). In addition, - Print the mapping pointer using %p insted of %px. The actual value of the pointer can be read out of the raw page dump and using %p gives a chance to correlate it with an earlier printk of the mapping pointer - Print the mapping pointer from the head page, not the tail page (the tail ->mapping pointer may be in use for other purposes, eg part of a list_head) - Print the order of the page for compound pages - Dump the raw head page as well as the raw page - Print the refcount from the head page, not the tail page Suggested-by:

Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Co-developed-by:

John Hubbard <jhubbard@nvidia.com> Signed-off-by:

Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by:

John Hubbard <jhubbard@nvidia.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Cc: Ira Weiny <ira.weiny@intel.com> Cc: Jan Kara <jack@suse.cz> Cc: Jérôme Glisse <jglisse@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@infradead.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Vlastimil Babka <vbabka@suse.cz> Link: http://lkml.kernel.org/r/20200211001536.1027652-12-jhubbard@nvidia.com Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/debug.c

+23 −10

Original line number	Diff line number	Diff line
		@@ -44,8 +44,10 @@ const struct trace_print_flags vmaflag_names[] = {

		void __dump_page(struct page page, const char reason)
		{
		struct page *head = compound_head(page);
		struct address_space *mapping;
		bool page_poisoned = PagePoisoned(page);
		bool compound = PageCompound(page);
		/*
		* Accessing the pageblock without the zone lock. It could change to
		* "isolate" again in the meantime, but since we are just dumping the
		@@ -66,25 +68,32 @@ void __dump_page(struct page page, const char reason)
		goto hex_only;
		}

		if (page < head \|\| (page >= head + MAX_ORDER_NR_PAGES)) {
		/* Corrupt page, cannot call page_mapping */
		mapping = page->mapping;
		head = page;
		compound = false;
		} else {
		mapping = page_mapping(page);
		}

		/*
		* Avoid VM_BUG_ON() in page_mapcount().
		* page->_mapcount space in struct page is used by sl[aou]b pages to
		* encode own info.
		*/
		mapcount = PageSlab(page) ? 0 : page_mapcount(page);
		mapcount = PageSlab(head) ? 0 : page_mapcount(page);

		if (PageCompound(page))
		pr_warn("page:%px refcount:%d mapcount:%d mapping:%px "
		"index:%#lx compound_mapcount: %d\n",
		page, page_ref_count(page), mapcount,
		page->mapping, page_to_pgoff(page),
		compound_mapcount(page));
		if (compound)
		pr_warn("page:%px refcount:%d mapcount:%d mapping:%p "
		"index:%#lx head:%px order:%u compound_mapcount:%d\n",
		page, page_ref_count(head), mapcount,
		mapping, page_to_pgoff(page), head,
		compound_order(head), compound_mapcount(page));
		else
		pr_warn("page:%px refcount:%d mapcount:%d mapping:%px index:%#lx\n",
		pr_warn("page:%px refcount:%d mapcount:%d mapping:%p index:%#lx\n",
		page, page_ref_count(page), mapcount,
		page->mapping, page_to_pgoff(page));
		mapping, page_to_pgoff(page));
		if (PageKsm(page))
		type = "ksm ";
		else if (PageAnon(page))
		@@ -106,6 +115,10 @@ hex_only:
		print_hex_dump(KERN_WARNING, "raw: ", DUMP_PREFIX_NONE, 32,
		sizeof(unsigned long), page,
		sizeof(struct page), false);
		if (head != page)
		print_hex_dump(KERN_WARNING, "head: ", DUMP_PREFIX_NONE, 32,
		sizeof(unsigned long), head,
		sizeof(struct page), false);

		if (reason)
		pr_warn("page dumped because: %s\n", reason);

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