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mm: improve dump_page() for compound pages

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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>
This commit is contained in:
Matthew Wilcox (Oracle) 2020-04-01 21:05:49 -07:00 committed by Linus Torvalds
parent be87141108
commit 6197ab984b
1 changed files with 23 additions and 10 deletions
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33
mm/debug.c
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@ -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;
}
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 @@ void __dump_page(struct page *page, const char *reason)
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);