From: John Hubbard <jhubbard@nvidia.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Al Viro" <viro@zeniv.linux.org.uk>,
"Christoph Hellwig" <hch@infradead.org>,
"Dan Williams" <dan.j.williams@intel.com>,
"Dave Chinner" <david@fromorbit.com>,
"Ira Weiny" <ira.weiny@intel.com>, "Jan Kara" <jack@suse.cz>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
"Jonathan Corbet" <corbet@lwn.net>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
"Michal Hocko" <mhocko@suse.com>,
"Mike Kravetz" <mike.kravetz@oracle.com>,
"Shuah Khan" <shuah@kernel.org>,
"Vlastimil Babka" <vbabka@suse.cz>,
"Matthew Wilcox" <willy@infradead.org>,
linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kselftest@vger.kernel.org, linux-rdma@vger.kernel.org,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
"John Hubbard" <jhubbard@nvidia.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Subject: [PATCH v4 01/12] mm: dump_page(): better diagnostics for compound pages
Date: Tue, 4 Feb 2020 15:41:06 -0800 [thread overview]
Message-ID: <20200204234117.2974687-2-jhubbard@nvidia.com> (raw)
In-Reply-To: <20200204234117.2974687-1-jhubbard@nvidia.com>
A compound page collects the refcount in the head page, while leaving
the refcount of each tail page at zero. Therefore, when debugging a
problem that involves compound pages, it's best to have diagnostics that
reflect that situation. However, dump_page() is oblivious to these
points.
Change dump_page() as follows:
1) For tail pages, print relevant head page information: refcount, in
particular. But only do this if the page is not corrupted so badly
that the pointer to the head page is all wrong.
2) Do a separate check to catch any (rare) cases of the tail page's
refcount being non-zero, and issue a separate, clear pr_warn() if
that ever happens.
Suggested-by: Matthew Wilcox <willy@infradead.org>
Suggested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
mm/debug.c | 35 +++++++++++++++++++++++++++++------
1 file changed, 29 insertions(+), 6 deletions(-)
diff --git a/mm/debug.c b/mm/debug.c
index ecccd9f17801..f074077eee11 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -42,6 +42,33 @@ const struct trace_print_flags vmaflag_names[] = {
{0, NULL}
};
+static void __dump_tail_page(struct page *page, int mapcount)
+{
+ struct page *head = compound_head(page);
+
+ if ((page < head) || (page >= head + MAX_ORDER_NR_PAGES)) {
+ /*
+ * Page is hopelessly corrupted, so limit any reporting to
+ * information about the page itself. Do not attempt to look at
+ * the head page.
+ */
+ pr_warn("page:%px refcount:%d mapcount:%d mapping:%px "
+ "index:%#lx (corrupted tail page case)\n",
+ page, page_ref_count(page), mapcount, page->mapping,
+ page_to_pgoff(page));
+ } else {
+ pr_warn("page:%px compound refcount:%d mapcount:%d mapping:%px "
+ "index:%#lx compound_mapcount:%d\n",
+ page, page_ref_count(head), mapcount, head->mapping,
+ page_to_pgoff(head), compound_mapcount(page));
+ }
+
+ if (page_ref_count(page) != 0) {
+ pr_warn("page:%px PROBLEM: non-zero refcount (==%d) on this "
+ "tail page\n", page, page_ref_count(page));
+ }
+}
+
void __dump_page(struct page *page, const char *reason)
{
struct address_space *mapping;
@@ -75,12 +102,8 @@ void __dump_page(struct page *page, const char *reason)
*/
mapcount = PageSlab(page) ? 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 (PageTail(page))
+ __dump_tail_page(page, mapcount);
else
pr_warn("page:%px refcount:%d mapcount:%d mapping:%px index:%#lx\n",
page, page_ref_count(page), mapcount,
--
2.25.0
next prev parent reply other threads:[~2020-02-04 23:42 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-04 23:41 [PATCH v4 00/12] mm/gup: track FOLL_PIN pages John Hubbard
2020-02-04 23:41 ` John Hubbard [this message]
2020-02-04 23:41 ` [PATCH v4 02/12] mm/gup: split get_user_pages_remote() into two routines John Hubbard
2020-02-04 23:41 ` [PATCH v4 03/12] mm/gup: pass a flags arg to __gup_device_* functions John Hubbard
2020-02-04 23:41 ` [PATCH v4 04/12] mm: introduce page_ref_sub_return() John Hubbard
2020-02-05 9:23 ` Jan Kara
2020-02-05 11:23 ` Kirill A. Shutemov
2020-02-04 23:41 ` [PATCH v4 05/12] mm/gup: pass gup flags to two more routines John Hubbard
2020-02-04 23:41 ` [PATCH v4 06/12] mm/gup: require FOLL_GET for get_user_pages_fast() John Hubbard
2020-02-04 23:41 ` [PATCH v4 07/12] mm/gup: track FOLL_PIN pages John Hubbard
2020-02-05 11:35 ` Kirill A. Shutemov
2020-02-04 23:41 ` [PATCH v4 08/12] mm/gup: page->hpage_pinned_refcount: exact pin counts for huge pages John Hubbard
2020-02-04 23:41 ` [PATCH v4 09/12] mm: dump_page(): better diagnostics for huge pinned pages John Hubbard
2020-02-04 23:41 ` [PATCH v4 10/12] mm/gup: /proc/vmstat: pin_user_pages (FOLL_PIN) reporting John Hubbard
2020-02-05 9:37 ` Jan Kara
2020-02-05 23:13 ` John Hubbard
2020-02-05 11:43 ` Kirill A. Shutemov
2020-02-05 23:58 ` John Hubbard
2020-02-04 23:41 ` [PATCH v4 11/12] mm/gup_benchmark: support pin_user_pages() and related calls John Hubbard
2020-02-05 11:46 ` Kirill A. Shutemov
2020-02-04 23:41 ` [PATCH v4 12/12] selftests/vm: run_vmtests: invoke gup_benchmark with basic FOLL_PIN coverage John Hubbard
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200204234117.2974687-2-jhubbard@nvidia.com \
--to=jhubbard@nvidia.com \
--cc=akpm@linux-foundation.org \
--cc=corbet@lwn.net \
--cc=dan.j.williams@intel.com \
--cc=david@fromorbit.com \
--cc=hch@infradead.org \
--cc=ira.weiny@intel.com \
--cc=jack@suse.cz \
--cc=jgg@ziepe.ca \
--cc=jglisse@redhat.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=kirill@shutemov.name \
--cc=linux-doc@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-rdma@vger.kernel.org \
--cc=mhocko@suse.com \
--cc=mike.kravetz@oracle.com \
--cc=shuah@kernel.org \
--cc=vbabka@suse.cz \
--cc=viro@zeniv.linux.org.uk \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).