Hi Matt, On Mon, Jul 26, 2021 at 12:27:50PM -0700, Matt Turner wrote: > Reply-To: > > Hi Mike! > > Since commit fa3354e4ea39 (mm: free_area_init: use maximal zone PFNs rather > than zone sizes), I get the following BUG on Alpha (an AlphaServer ES47 Marvel) > and loading userspace leads to a segfault: > > (I didn't notice this for a long time because of other unrelated regressions, > the pandemic, changing jobs, ...) I suspect there will be more surprises down the road :) > BUG: Bad page state in process swapper pfn:2ffc53 > page:fffffc000ecf14c0 refcount:0 mapcount:1 mapping:0000000000000000 index:0x0 > flags: 0x0() > raw: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 > raw: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 > page dumped because: nonzero mapcount Modules linked in: > CPU: 0 PID: 0 Comm: swapper Not tainted 5.7.0-03841-gfa3354e4ea39-dirty #26 > fffffc0001b5bd68 fffffc0001b5be80 fffffc00011cd148 fffffc000ecf14c0 > fffffc00019803df fffffc0001b5be80 fffffc00011ce340 fffffc000ecf14c0 > 0000000000000000 fffffc0001b5be80 fffffc0001b482c0 fffffc00027d6618 > fffffc00027da7d0 00000000002ff97a 0000000000000000 fffffc0001b5be80 > fffffc00011d1abc fffffc000ecf14c0 fffffc0002d00000 fffffc0001b5be80 > fffffc0001b2350c 0000000000300000 fffffc0001b48298 fffffc0001b482c0 > Trace: > [<fffffc00011cd148>] bad_page+0x168/0x1b0 > [<fffffc00011ce340>] free_pcp_prepare+0x1e0/0x290 > [<fffffc00011d1abc>] free_unref_page+0x2c/0xa0 > [<fffffc00014ee5f0>] cmp_ex_sort+0x0/0x30 > [<fffffc00014ee5f0>] cmp_ex_sort+0x0/0x30 > [<fffffc000101001c>] _stext+0x1c/0x20 > > I haven't tried reproducing this on other machines or QEMU, but I'd be glad to > if that helps. If it's reproducible on QEMU I can debug it locally. > Any ideas? It seems like memory map is not properly initialized. Can you enable CONFIG_DEBUG_MEMORY_INIT and add mminit_debug=4 to the command line. The interesting part of the log would be before "Memory: xK/yK available ..." line. Hopefully it'll give some clues. -- Sincerely yours, Mike.
