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| author | Matthew Wilcox (Oracle) <willy@infradead.org> | 2020-08-06 23:19:32 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-08-07 11:33:23 -0700 |
| commit | e1ab96f8cc713c673df4ab806bd90918e5ab6c98 (patch) | |
| tree | 094ec0616606308e6b8e3227138f21bba7f23d5e /mm/debug.c | |
| parent | b1d00007f2126e045c465daf754df43ba74ddcdd (diff) | |
| download | lwn-e1ab96f8cc713c673df4ab806bd90918e5ab6c98.tar.gz lwn-e1ab96f8cc713c673df4ab806bd90918e5ab6c98.zip | |
mm/debug: handle page->mapping better in dump_page
Patch series "Improvements for dump_page()", v2.
Here's a sample dump of a pagecache tail page with all of the patches
applied:
page:000000006d1c49ca refcount:6 mapcount:0 mapping:00000000136b8d90 index:0x109 pfn:0x6c645
head:000000008bd38076 order:2 compound_mapcount:0 compound_pincount:0
aops:xfs_address_space_operations ino:800042 dentry name:"fd"
flags: 0x4000000000012014(uptodate|lru|private|head)
raw: 4000000000000000 ffffd46ac1b19101 ffffffff00000202 dead000000000004
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
head: 4000000000012014 ffffd46ac1b1bbc8 ffffd46ac1b1bc08 ffff91976f659560
head: 0000000000000108 ffff919773220680 00000006ffffffff 0000000000000000
page dumped because: testing
This patch (of 6):
If we can't call page_mapping() to get the page mapping, handle the
anon/ksm/movable bits correctly.
[akpm@linux-foundation.org: augmented code comment from John]
Link: http://lkml.kernel.org/r/15cff11a-6762-8a6a-3f0e-dd227280cd6f@nvidia.com
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Link: http://lkml.kernel.org/r/20200709202117.7216-1-willy@infradead.org
Link: http://lkml.kernel.org/r/20200709202117.7216-2-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/debug.c')
| -rw-r--r-- | mm/debug.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/mm/debug.c b/mm/debug.c index 4f376514744d..567b80b0b9e4 100644 --- a/mm/debug.c +++ b/mm/debug.c @@ -69,8 +69,19 @@ void __dump_page(struct page *page, const char *reason) } if (page < head || (page >= head + MAX_ORDER_NR_PAGES)) { - /* Corrupt page, cannot call page_mapping */ - mapping = page->mapping; + /* + * Corrupt page, so we cannot call page_mapping. Instead, do a + * safe subset of the steps that page_mapping() does. Caution: + * this will be misleading for tail pages, PageSwapCache pages, + * and potentially other situations. (See the page_mapping() + * implementation for what's missing here.) + */ + unsigned long tmp = (unsigned long)page->mapping; + + if (tmp & PAGE_MAPPING_ANON) + mapping = NULL; + else + mapping = (void *)(tmp & ~PAGE_MAPPING_FLAGS); head = page; compound = false; } else { |