Re: Regression bisected to fa3354e4ea39 (mm: free_area_init: use maximal zone PFNs rather than zone sizes)

[Mike Rapoport]

On Mon, Jul 26, 2021 at 02:23:20PM -0700, Matt Turner wrote:
> On Mon, Jul 26, 2021 at 1:06 PM Mike Rapoport <rppt@xxxxxxxxxxxxx> wrote:
> >
> > 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.
> 
> Sure thing. Please find attached.

> aboot: loading uncompressed vmlinuz-5.7.0-03841-gfa3354e4ea39-dirty...
> aboot: loading compressed vmlinuz-5.7.0-03841-gfa3354e4ea39-dirty...
> aboot: PHDR 0 vaddr 0xfffffc0001010000 offset 0xc0 size 0x17c5ae0
> aboot: bss at 0xfffffc00027d5ae0, size 0xe4ea0
> aboot: zero-filling 937632 bytes at 0xfffffc00027d5ae0
> aboot: loading initrd (5965252 bytes/5825 blocks) at 0xfffffc05ff2cc000
> aboot: starting kernel vmlinuz-5.7.0-03841-gfa3354e4ea39-dirty with arguments ro panic=5 domdadm root=/dev/md1 console=srm  mminit_debug=4
> Linux version 5.7.0-03841-gfa3354e4ea39-dirty (mattst88@ivybridge) (gcc version 11.1.0 (Gentoo 11.1.0-r2 p3), GNU ld (Gentoo 2.36.1 p3) 2.36.1) #26 SMP Sun Jul 25 18:20:06 PDT 2021
> printk: bootconsole [srm0] enabled
> Booting on Marvel variation Marvel/EV7 using machine vector MARVEL/EV7 from SRM
> Major Options: SMP EV67 VERBOSE_MCHECK DEBUG_SPINLOCK MAGIC_SYSRQ 
> Command line: ro panic=5 domdadm root=/dev/md1 console=srm  mminit_debug=4
> memcluster 0, usage 1, start        0, end     1984
> memcluster 1, usage 0, start     1984, end  1048576
> memcluster 2, usage 1, start  2097152, end  2097224
> memcluster 3, usage 0, start  2097224, end  3145728
> Initial ramdisk at: 0x(____ptrval____) (5965252 bytes)
> Found an IO7 at PID 0
> Initializing IO7 at PID 0
> FIXME: disabling master aborts
> FIXME: disabling master aborts
> FIXME: disabling master aborts
> FIXME: disabling master aborts
> SMP: 2 CPUs probed -- cpu_present_mask = 3
> Zone ranges:
>   DMA      [mem 0x0000000000f80000-0x00000fffffffdfff]
>   Normal   empty
> Movable zone start for each node
> Early memory node ranges
>   node   0: [mem 0x0000000000f80000-0x00000001ffffffff]
>   node   0: [mem 0x0000000400090000-0x00000005ffffffff]

I think that the issue is that memory marked as used in memcluster is never
added to memblock and it skews node/zone sizing calculations.

Can you try this patch:

diff --git a/arch/alpha/kernel/setup.c b/arch/alpha/kernel/setup.c
index 7d56c217b235..b4fbbba30aa2 100644
--- a/arch/alpha/kernel/setup.c
+++ b/arch/alpha/kernel/setup.c
@@ -319,18 +319,19 @@ setup_memory(void *kernel_end)
 		       i, cluster->usage, cluster->start_pfn,
 		       cluster->start_pfn + cluster->numpages);
 
-		/* Bit 0 is console/PALcode reserved.  Bit 1 is
-		   non-volatile memory -- we might want to mark
-		   this for later.  */
-		if (cluster->usage & 3)
-			continue;
-
 		end = cluster->start_pfn + cluster->numpages;
 		if (end > max_low_pfn)
 			max_low_pfn = end;
 
 		memblock_add(PFN_PHYS(cluster->start_pfn),
 			     cluster->numpages << PAGE_SHIFT);
+
+		/* Bit 0 is console/PALcode reserved.  Bit 1 is
+		   non-volatile memory -- we might want to mark
+		   this for later.  */
+		if (cluster->usage & 3)
+			memblock_reserve(PFN_PHYS(cluster->start_pfn),
+				         cluster->numpages << PAGE_SHIFT);
 	}
 
 	/*

> Initmem setup node 0 [mem 0x0000000000f80000-0x00000005ffffffff]
> percpu: Embedded 8 pages/cpu s27648 r8192 d29696 u65536
> Built 1 zonelists, mobility grouping on.  Total pages: 2070535
> Kernel command line: ro panic=5 domdadm root=/dev/md1 console=srm  mminit_debug=4
> Dentry cache hash table entries: 2097152 (order: 11, 16777216 bytes, linear)
> Inode-cache hash table entries: 1048576 (order: 10, 8388608 bytes, linear)
> Sorting __ex_table...
> mem auto-init: stack:off, heap alloc:off, heap free:off
> BUG: Bad page state in process swapper  pfn:2ffc3f
> page:fffffc000ecf0fc0 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 fffffc000ecf0fc0
>        fffffc00019803df fffffc0001b5be80 fffffc00011ce340 fffffc000ecf0fc0
>        0000000000000000 fffffc0001b5be80 fffffc0001b482c0 fffffc00027d6618
>        fffffc00027da7d0 00000000002ff966 0000000000000000 fffffc0001b5be80
>        fffffc00011d1abc fffffc000ecf0fc0 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

...

> Memory: 16496504K/16760768K available (8698K kernel code, 12790K rwdata, 2544K rodata, 304K init, 915K bss, 256576K reserved, 0K cma-reserved)


-- 
Sincerely yours,
Mike.