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SubjectRe: [PATCH] Revert "mm/cma: manage the memory of the CMA area by using the ZONE_MOVABLE"
On Thu, May 17, 2018 at 10:53:32AM -0700, Laura Abbott wrote:
> On 05/17/2018 10:08 AM, Michal Hocko wrote:
> >On Thu 17-05-18 18:49:47, Michal Hocko wrote:
> >>On Thu 17-05-18 16:58:32, Ville Syrjälä wrote:
> >>>On Thu, May 17, 2018 at 04:36:29PM +0300, Ville Syrjälä wrote:
> >>>>On Thu, May 17, 2018 at 03:21:09PM +0200, Michal Hocko wrote:
> >>>>>On Thu 17-05-18 15:59:59, Ville Syrjala wrote:
> >>>>>>From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >>>>>>
> >>>>>>This reverts commit bad8c6c0b1144694ecb0bc5629ede9b8b578b86e.
> >>>>>>
> >>>>>>Make x86 with HIGHMEM=y and CMA=y boot again.
> >>>>>
> >>>>>Is there any bug report with some more details? It is much more
> >>>>>preferable to fix the issue rather than to revert the whole thing
> >>>>>right away.
> >>>>
> >>>>The machine I have in front of me right now didn't give me anything.
> >>>>Black screen, and netconsole was silent. No serial port on this
> >>>>machine unfortunately.
> >>>
> >>>Booted on another machine with serial:
> >>
> >>Could you provide your .config please?
> >>
> >>[...]
> >>>[ 0.000000] cma: Reserved 4 MiB at 0x0000000037000000
> >>[...]
> >>>[ 0.000000] BUG: Bad page state in process swapper pfn:377fe
> >>>[ 0.000000] page:f53effc0 count:0 mapcount:-127 mapping:00000000 index:0x0
> >>
> >>OK, so this looks the be the source of the problem. -128 would be a
> >>buddy page but I do not see anything that would set the counter to -127
> >>and the real map count updates shouldn't really happen that early.
> >>
> >>Maybe CONFIG_DEBUG_VM and CONFIG_DEBUG_HIGHMEM will tell us more.
> >
> >Looking closer, I _think_ that the bug is in set_highmem_pages_init->is_highmem
> >and zone_movable_is_highmem might force CMA pages in the zone movable to
> >be initialized as highmem. And that sounds supicious to me. Joonsoo?
> >
>
> For a point of reference, arm with this configuration doesn't hit this bug
> because highmem pages are freed via the memblock interface only instead
> of iterating through each zone. It looks like the x86 highmem code
> assumes only a single highmem zone and/or it's disjoint?

Good point! Reason of the crash is that the span of MOVABLE_ZONE is
extended to whole node span for future CMA initialization, and,
normal memory is wrongly freed here.

Here goes the fix. Ville, Could you test below patch?
I re-generated the issue on my side and this patch fixed it.

Thanks.

------------>8-------------
From 569899a4dbd28cebb8d350d3d1ebb590d88b2629 Mon Sep 17 00:00:00 2001
From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Date: Fri, 18 May 2018 10:52:05 +0900
Subject: [PATCH] x86/32/highmem: check if the zone is matched when free
highmem pages on init

If CONFIG_CMA is enabled, it extends the span of the MOVABLE_ZONE
to manage the CMA memory later. And, in this case, the span of the
MOVABLE_ZONE could overlap the other zone's memory. We need to
avoid freeing this overlapped memory here since it would be the
memory of the other zone. Therefore, this patch adds a check
whether the page is indeed on the requested zone or not. Skipped
page will be freed when the memory of the matched zone is freed.

Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
---
arch/x86/include/asm/highmem.h | 4 ++--
arch/x86/mm/highmem_32.c | 5 ++++-
arch/x86/mm/init_32.c | 25 +++++++++++++++++++++----
3 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/highmem.h b/arch/x86/include/asm/highmem.h
index a805993..e383f57 100644
--- a/arch/x86/include/asm/highmem.h
+++ b/arch/x86/include/asm/highmem.h
@@ -72,8 +72,8 @@ void *kmap_atomic_prot_pfn(unsigned long pfn, pgprot_t prot);

#define flush_cache_kmaps() do { } while (0)

-extern void add_highpages_with_active_regions(int nid, unsigned long start_pfn,
- unsigned long end_pfn);
+extern void add_highpages_with_active_regions(int nid, struct zone *zone,
+ unsigned long start_pfn, unsigned long end_pfn);

#endif /* __KERNEL__ */

diff --git a/arch/x86/mm/highmem_32.c b/arch/x86/mm/highmem_32.c
index 6d18b70..bf9f5b8 100644
--- a/arch/x86/mm/highmem_32.c
+++ b/arch/x86/mm/highmem_32.c
@@ -120,6 +120,9 @@ void __init set_highmem_pages_init(void)
if (!is_highmem(zone))
continue;

+ if (!populated_zone(zone))
+ continue;
+
zone_start_pfn = zone->zone_start_pfn;
zone_end_pfn = zone_start_pfn + zone->spanned_pages;

@@ -127,7 +130,7 @@ void __init set_highmem_pages_init(void)
printk(KERN_INFO "Initializing %s for node %d (%08lx:%08lx)\n",
zone->name, nid, zone_start_pfn, zone_end_pfn);

- add_highpages_with_active_regions(nid, zone_start_pfn,
+ add_highpages_with_active_regions(nid, zone, zone_start_pfn,
zone_end_pfn);
}
}
diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index 8008db2..f646072 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -431,7 +431,7 @@ static void __init permanent_kmaps_init(pgd_t *pgd_base)
pkmap_page_table = pte;
}

-void __init add_highpages_with_active_regions(int nid,
+void __init add_highpages_with_active_regions(int nid, struct zone *zone,
unsigned long start_pfn, unsigned long end_pfn)
{
phys_addr_t start, end;
@@ -442,9 +442,26 @@ void __init add_highpages_with_active_regions(int nid,
start_pfn, end_pfn);
unsigned long e_pfn = clamp_t(unsigned long, PFN_DOWN(end),
start_pfn, end_pfn);
- for ( ; pfn < e_pfn; pfn++)
- if (pfn_valid(pfn))
- free_highmem_page(pfn_to_page(pfn));
+ for ( ; pfn < e_pfn; pfn++) {
+ struct page *page;
+
+ if (!pfn_valid(pfn))
+ continue;
+
+ page = pfn_to_page(pfn);
+
+ /*
+ * If CONFIG_CMA is enabled, it extends the span of
+ * the MOVABLE_ZONE to manage the CMA memory
+ * in the future. And, in this case, the span of the
+ * MOVABLE_ZONE could overlap the other zone's memory.
+ * We need to avoid freeing this memory here.
+ */
+ if (IS_ENABLED(CONFIG_CMA) && page_zone(page) != zone)
+ continue;
+
+ free_highmem_page(pfn_to_page(pfn));
+ }
}
}
#else
--
2.7.4
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