On Mon, Jun 04, 2018 at 06:18:36PM -0700, Matthew Wilcox wrote: > On Tue, Jun 05, 2018 at 12:54:03AM +0000, Naoya Horiguchi wrote: > > Reproduction precedure is like this: > > - enable RAM based PMEM (with a kernel boot parameter like memmap=1G!4G) > > - read /proc/kpageflags (or call tools/vm/page-types with no arguments) > > (- my kernel config is attached) > > > > I spent a few days on this, but didn't reach any solutions. > > So let me report this with some details below ... > > > > In the critial page request, stable_page_flags() is called with an argument > > page whose ->compound_head was somehow filled with '0xffffffffffffffff'. > > And compound_head() returns (struct page *)(head - 1), which explains the > > address 0xfffffffffffffffe in the above message. > > Hm. compound_head shares with: > > struct list_head lru; > struct list_head slab_list; /* uses lru */ > struct { /* Partial pages */ > struct page *next; > unsigned long _compound_pad_1; /* compound_head */ > unsigned long _pt_pad_1; /* compound_head */ > struct dev_pagemap *pgmap; > struct rcu_head rcu_head; > > None of them should be -1. > > > It seems that this kernel panic happens when reading kpageflags of pfn range > > [0xbffd7, 0xc0000), which coresponds to a 'reserved' range. > > > > [ 0.000000] user-defined physical RAM map: > > [ 0.000000] user: [mem 0x0000000000000000-0x000000000009fbff] usable > > [ 0.000000] user: [mem 0x000000000009fc00-0x000000000009ffff] reserved > > [ 0.000000] user: [mem 0x00000000000f0000-0x00000000000fffff] reserved > > [ 0.000000] user: [mem 0x0000000000100000-0x00000000bffd6fff] usable > > [ 0.000000] user: [mem 0x00000000bffd7000-0x00000000bfffffff] reserved > > [ 0.000000] user: [mem 0x00000000feffc000-0x00000000feffffff] reserved > > [ 0.000000] user: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved > > [ 0.000000] user: [mem 0x0000000100000000-0x000000013fffffff] persistent > > (type 12) > > > > So I guess 'memmap=' parameter might badly affect the memory initialization > > process. > > > > This problem doesn't reproduce on v4.17, so some pre-released patch > > introduces it. > > I hope this info helps you find the solution/workaround. > > Can you try bisecting this? It could be one of my patches to reorder struct > page, or it could be one of Pavel's deferred page initialisation patches. > Or something else ;-)
Thank you for the comment. I'm trying bisecting now, let you know the result later. And I found that my statement "not reproduce on v4.17" was wrong (I used different kvm guests, which made some different test condition and misguided me), this seems an older (at least < 4.15) bug. Thanks, Naoya Horiguchi