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SubjectRe: [PATCH] mm, debug: always print flags in dump_page()
On Tue 14-01-20 13:04:31, Vlastimil Babka wrote:
[...]
> >From 7b673c45bc16526586ae8ea6fba416a547baa04e Mon Sep 17 00:00:00 2001
> From: Vlastimil Babka <vbabka@suse.cz>
> Date: Tue, 14 Jan 2020 12:52:48 +0100
> Subject: [PATCH] mm, debug: always print flags in dump_page()
>
> Commit 76a1850e4572 ("mm/debug.c: __dump_page() prints an extra line")
> inadvertently removed printing of page flags for pages that are neither
> anon nor ksm nor have a mapping. Fix that.
>
> Using pr_cont() again would be a solution, but the commit explicitly removed
> its use. Avoiding the danger of mixing up split lines from multiple CPUs might
> be beneficial for near-panic dumps like this, so fix this without reintroducing
> pr_cont().
>
> Reported-by: Anshuman Khandual <anshuman.khandual@arm.com>
> Reported-by: Michal Hocko <mhocko@kernel.org>
> Fixes: 76a1850e4572 ("mm/debug.c: __dump_page() prints an extra line")
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Acked-by: Michal Hocko <mhocko@suse.com>

Thanks!

> ---
> mm/debug.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/mm/debug.c b/mm/debug.c
> index 0461df1207cb..6a52316af839 100644
> --- a/mm/debug.c
> +++ b/mm/debug.c
> @@ -47,6 +47,7 @@ void __dump_page(struct page *page, const char *reason)
> struct address_space *mapping;
> bool page_poisoned = PagePoisoned(page);
> int mapcount;
> + char *type = "";
>
> /*
> * If struct page is poisoned don't access Page*() functions as that
> @@ -78,9 +79,9 @@ void __dump_page(struct page *page, const char *reason)
> page, page_ref_count(page), mapcount,
> page->mapping, page_to_pgoff(page));
> if (PageKsm(page))
> - pr_warn("ksm flags: %#lx(%pGp)\n", page->flags, &page->flags);
> + type = "ksm ";
> else if (PageAnon(page))
> - pr_warn("anon flags: %#lx(%pGp)\n", page->flags, &page->flags);
> + type = "anon ";
> else if (mapping) {
> if (mapping->host && mapping->host->i_dentry.first) {
> struct dentry *dentry;
> @@ -88,10 +89,11 @@ void __dump_page(struct page *page, const char *reason)
> pr_warn("%ps name:\"%pd\"\n", mapping->a_ops, dentry);
> } else
> pr_warn("%ps\n", mapping->a_ops);
> - pr_warn("flags: %#lx(%pGp)\n", page->flags, &page->flags);
> }
> BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1);
>
> + pr_warn("%sflags: %#lx(%pGp)\n", type, page->flags, &page->flags);
> +
> hex_only:
> print_hex_dump(KERN_WARNING, "raw: ", DUMP_PREFIX_NONE, 32,
> sizeof(unsigned long), page,
> --
> 2.24.1

--
Michal Hocko
SUSE Labs

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