From 46e8a3a08c23d07d0f21fabeed182b671af68c93 Mon Sep 17 00:00:00 2001 From: Vlastimil Babka Date: Mon, 12 Dec 2016 16:44:35 -0800 Subject: [PATCH] mm, debug: print raw struct page data in __dump_page() __dump_page() is used when a page metadata inconsistency is detected, either by standard runtime checks, or extra checks in CONFIG_DEBUG_VM builds. It prints some of the relevant metadata, but not the whole struct page, which is based on unions and interpretation is dependent on the context. This means that sometimes e.g. a VM_BUG_ON_PAGE() checks certain field, which is however not printed by __dump_page() and the resulting bug report may then lack clues that could help in determining the root cause. This patch solves the problem by simply printing the whole struct page word by word, so no part is missing, but the interpretation of the data is left to developers. This is similar to e.g. x86_64 raw stack dumps. Example output: page:ffffea00000475c0 count:1 mapcount:0 mapping: (null) index:0x0 flags: 0x100000000000400(reserved) raw: 0100000000000400 0000000000000000 0000000000000000 00000001ffffffff raw: ffffea00000475e0 ffffea00000475e0 0000000000000000 0000000000000000 page dumped because: VM_BUG_ON_PAGE(1) [aryabinin@virtuozzo.com: suggested print_hex_dump()] Link: http://lkml.kernel.org/r/2ff83214-70fe-741e-bf05-fe4a4073ec3e@suse.cz Signed-off-by: Vlastimil Babka Acked-by: Kirill A. Shutemov Acked-by: Andrey Ryabinin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/debug.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/debug.c b/mm/debug.c index 9feb699c5d25..db1cd26d8752 100644 --- a/mm/debug.c +++ b/mm/debug.c @@ -59,6 +59,10 @@ void __dump_page(struct page *page, const char *reason) pr_emerg("flags: %#lx(%pGp)\n", page->flags, &page->flags); + print_hex_dump(KERN_ALERT, "raw: ", DUMP_PREFIX_NONE, 32, + sizeof(unsigned long), page, + sizeof(struct page), false); + if (reason) pr_alert("page dumped because: %s\n", reason);