Re: [BISECTED][REGRESSION] 5.10.56 longterm kernel breakage on m68k/aranym

[Mike Rapoport <rppt@kernel.org>]

On Mon, Aug 09, 2021 at 03:40:04PM +0200, Geert Uytterhoeven wrote:
> CC Mike
> 
> On Mon, Aug 9, 2021 at 3:32 PM Mikael Pettersson <mikpelinux@gmail.com> wrote:
> > On Mon, Aug 9, 2021 at 3:59 AM Finn Thain <fthain@linux-m68k.org> wrote:
> > > On Sun, 8 Aug 2021, Mikael Pettersson wrote:
> > > > On Sun, Aug 8, 2021 at 1:20 AM Finn Thain <fthain@linux-m68k.org> wrote:
> > > > > On Sat, 7 Aug 2021, Mikael Pettersson wrote:
> > > > > > I updated the 5.10 longterm kernel on one of my m68k/aranym VMs from
> > > > > > 5.10.47 to 5.10.56, and the new kernel failed to boot:
> > > > > >
> > > > > > ARAnyM 1.1.0
> > > > > > Using config file: 'aranym1.headless.config'
> > > > > > Could not open joystick 0
> > > > > > ARAnyM RTC Timer: /dev/rtc: Permission denied
> > > > > > ARAnyM LILO: Error loading ramdisk 'root.bin'
> > > > > > Blitter tried to read byte from register ff8a00 at 0077ee
> > > > > >
> > > > > > At this point it kept running, but produced no output to the console,
> > > > > > and would never get to the point of starting user-space. Attaching gdb
> > > > > > to aranym showed nothing interesting, i.e. it seemed to be executing
> > > > > > normally.
> >
> > My initial bisect was wrong. I tried reverting 8f34f1eac382 from
> > 5.10.57 but that made no difference, so I re-ran the git bisect with
> > all known good points pre-marked. This landed on:
> > # first bad commit: [ce6ee46e0f39ed97e23ebf7b5a565e0266a8a1a3]
> > mm/page_alloc: fix memory map initialization for descending nodes
> >
> > Reverting _that_ from 5.10.57 does unbreak that kernel.

Indeed there is a problem with that commit in 5.10. The memmap
initialization relies on availability of zone_to_nid() to link struct page
to a node. But in 5.10 zone_to_nid() is only defined for NUMA, but not for
DISCONTIGMEM.

Mikael, can you please try the patch below:

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 9d0c454d23cd..63b550403317 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -445,7 +445,7 @@ struct zone {
 	 */
 	long lowmem_reserve[MAX_NR_ZONES];
 
-#ifdef CONFIG_NUMA
+#ifdef CONFIG_NEED_MULTIPLE_NODES
 	int node;
 #endif
 	struct pglist_data	*zone_pgdat;
@@ -896,7 +896,7 @@ static inline bool populated_zone(struct zone *zone)
 	return zone->present_pages;
 }
 
-#ifdef CONFIG_NUMA
+#ifdef CONFIG_NEED_MULTIPLE_NODES
 static inline int zone_to_nid(struct zone *zone)
 {
 	return zone->node;

-- 
Sincerely yours,
Mike.