Re: [v6 04/15] mm: discard memblock data later

Pasha Tatashin
2017-08-11T15:50:42Z

> I guess this goes all the way down to
> Fixes: 7e18adb4f80b ("mm: meminit: initialise remaining struct pages in parallel with kswapd")

I will add this to the patch.

>> Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
>> Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
>> Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
>> Reviewed-by: Bob Picco <bob.picco@oracle.com>
>
> Considering that some HW might behave strangely and this would be rather
> hard to debug I would be tempted to mark this for stable. It should also
> be merged separately from the rest of the series.
>
> I have just one nit below
> Acked-by: Michal Hocko <mhocko@suse.com>

I will address your comment, and send out a new patch. Should I send it
out separately from the series or should I keep it inside?

Also, before I send out a new patch, I will need to root cause and
resolve problem found by kernel test robot <fengguang.wu@intel.com>, and
bisected down to this patch.

[ 156.659400] BUG: Bad page state in process swapper pfn:03147
[ 156.660051] page:ffff88001ed8a1c0 count:0 mapcount:-127 mapping:
(null) index:0x1
[ 156.660917] flags: 0x0()
[ 156.661198] raw: 0000000000000000 0000000000000000 0000000000000001
00000000ffffff80
[ 156.662006] raw: ffff88001f4a8120 ffff88001ed85ce0 0000000000000000
0000000000000000
[ 156.662811] page dumped because: nonzero mapcount
[ 156.663307] CPU: 0 PID: 1 Comm: swapper Not tainted
4.13.0-rc3-00220-g1aad694 #1
[ 156.664077] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.9.3-20161025_171302-gandalf 04/01/2014
[ 156.665129] Call Trace:
[ 156.665422] dump_stack+0x1e/0x20
[ 156.665802] bad_page+0x122/0x148

I was not able to reproduce this problem, even-though I used their qemu
script and config. But I am getting the following panic both base and fix:

[ 115.763259] VFS: Cannot open root device "ram0" or
unknown-block(0,0): error -6
[ 115.764511] Please append a correct "root=" boot option; here are the
available partitions:
[ 115.765816] Kernel panic - not syncing: VFS: Unable to mount root fs
on unknown-block(0,0)
[ 115.767124] CPU: 0 PID: 1 Comm: swapper Not tainted
4.13.0-rc4_pt_memset6-00033-g7e65200b1473 #7
[ 115.768506] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS rel-1.10.2-0-g5f4c7b1-prebuilt.qemu-project.org 04/01/2014
[ 115.770368] Call Trace:
[ 115.770771] dump_stack+0x1e/0x20
[ 115.771310] panic+0xf8/0x2bc
[ 115.771792] mount_block_root+0x3bb/0x441
[ 115.772437] ? do_early_param+0xc5/0xc5
[ 115.773051] ? do_early_param+0xc5/0xc5
[ 115.773683] mount_root+0x7c/0x7f
[ 115.774243] prepare_namespace+0x194/0x1d1
[ 115.774898] kernel_init_freeable+0x1c8/0x1df
[ 115.775575] ? rest_init+0x13f/0x13f
[ 115.776153] kernel_init+0x14/0x142
[ 115.776711] ? rest_init+0x13f/0x13f
[ 115.777285] ret_from_fork+0x2a/0x40
[ 115.777864] Kernel Offset: disabled

Their config has CONFIG_BLK_DEV_RAM disabled, but qemu script has:
root=/dev/ram0, so I enabled dev_ram, but still getting a panic when
root is mounted both in base and fix.

Pasha