The patch titled
Subject: mm: improve dump_page() for compound pages
has been added to the -mm tree. Its filename is
mm-improve-dump_page-for-compound-pages.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-improve-dump_page-for-compound-pages.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-improve-dump_page-for-compound-pages.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Subject: mm: improve dump_page() for compound pages
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
Link: http://lkml.kernel.org/r/20200211001536.1027652-12-jhubbard@xxxxxxxxxx
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
Co-developed-by: John Hubbard <jhubbard@xxxxxxxxxx>
Suggested-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Jérôme Glisse <jglisse@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/debug.c | 33 +++++++++++++++++++++++----------
1 file changed, 23 insertions(+), 10 deletions(-)
--- a/mm/debug.c~mm-improve-dump_page-for-compound-pages
+++ a/mm/debug.c
@@ -44,8 +44,10 @@ const struct trace_print_flags vmaflag_n
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, cons
goto hex_only;
}
- mapping = page_mapping(page);
+ 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);
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
mm-improve-dump_page-for-compound-pages.patch
