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Message-Id: <1444253335-5811-1-git-send-email-labbott@fedoraproject.org>
Date: Wed, 7 Oct 2015 14:28:55 -0700
From: Laura Abbott <labbott@...oraproject.org>
To: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
Vlastimil Babka <vbabka@...e.cz>,
Bjorn Andersson <bjorn.andersson@...ymobile.com>
Cc: Laura Abbott <laura@...bott.name>,
Santosh Shilimkar <ssantosh@...nel.org>,
Russell King <rmk@....linux.org.uk>,
Kevin Hilman <khilman@...aro.org>,
Arnd Bergman <arnd@...db.de>,
Stephen Boyd <sboyd@...eaurora.org>,
Andy Gross <agross@...eaurora.org>,
Mel Gorman <mgorman@...e.de>,
Steven Rostedt <rostedt@...dmis.org>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
Laura Abbott <lauraa@...eaurora.org>
Subject: [PATCHv4] mm: Don't offset memmap for flatmem
From: Laura Abbott <laura@...bott.name>
Srinivas Kandagatla reported bad page messages when trying to
remove the bottom 2MB on an ARM based IFC6410 board
BUG: Bad page state in process swapper pfn:fffa8
page:ef7fb500 count:0 mapcount:0 mapping: (null) index:0x0
flags: 0x96640253(locked|error|dirty|active|arch_1|reclaim|mlocked)
page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
bad because of flags:
flags: 0x200041(locked|active|mlocked)
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Not tainted 3.19.0-rc3-00007-g412f9ba-dirty #816
Hardware name: Qualcomm (Flattened Device Tree)
[<c0218280>] (unwind_backtrace) from [<c0212be8>] (show_stack+0x20/0x24)
[<c0212be8>] (show_stack) from [<c0af7124>] (dump_stack+0x80/0x9c)
[<c0af7124>] (dump_stack) from [<c0301570>] (bad_page+0xc8/0x128)
[<c0301570>] (bad_page) from [<c03018a8>] (free_pages_prepare+0x168/0x1e0)
[<c03018a8>] (free_pages_prepare) from [<c030369c>] (free_hot_cold_page+0x3c/0x174)
[<c030369c>] (free_hot_cold_page) from [<c0303828>] (__free_pages+0x54/0x58)
[<c0303828>] (__free_pages) from [<c030395c>] (free_highmem_page+0x38/0x88)
[<c030395c>] (free_highmem_page) from [<c0f62d5c>] (mem_init+0x240/0x430)
[<c0f62d5c>] (mem_init) from [<c0f5db3c>] (start_kernel+0x1e4/0x3c8)
[<c0f5db3c>] (start_kernel) from [<80208074>] (0x80208074)
Disabling lock debugging due to kernel taint
Removing the lower 2MB made the start of the lowmem zone to no longer
be page block aligned. IFC6410 uses CONFIG_FLATMEM where
alloc_node_mem_map allocates memory for the mem_map. alloc_node_mem_map
will offset for unaligned nodes with the assumption the pfn/page
translation functions will account for the offset. The functions for
CONFIG_FLATMEM do not offset however, resulting in overrunning
the memmap array. Just use the allocated memmap without any offset
when running with CONFIG_FLATMEM to avoid the overrun.
Signed-off-by: Laura Abbott <laura@...bott.name>
Signed-off-by: Laura Abbott <lauraa@...eaurora.org>
Reported-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Tested-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Acked-by: Vlastimil Babka <vbabka@...e.cz>
Tested-by: Bjorn Andersson <bjorn.andersson@...ymobile.com>
---
I was reminded at Linaro Connect that I never followed up on this patch.
v3 (http://marc.info/?l=linux-mm&m=142629173021316&w=2)
was dropped due to crashing (https://lkml.org/lkml/2015/3/20/546)
The fundamentals of the patch were fine, the VM_BUG_ON I added turned out
to be incorrect. It was supposed to be a sanity check but it didn't
actually hold true in all cases (or even most cases...) v4 just drops
the sanity check. I verified that the offset is working on both ARM, x86,
and i386 QEMU with the config provided by Steven Rostedt.
Since this was minor diff from the previous patch, I kept all the previous
Acked-by/Tested-by.
---
mm/page_alloc.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 40e2942..9e5ba5e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4953,6 +4953,8 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat,
static void __init_refok alloc_node_mem_map(struct pglist_data *pgdat)
{
+ unsigned long __maybe_unused offset = 0;
+
/* Skip empty nodes */
if (!pgdat->node_spanned_pages)
return;
@@ -4969,6 +4971,7 @@ static void __init_refok alloc_node_mem_map(struct pglist_data *pgdat)
* for the buddy allocator to function correctly.
*/
start = pgdat->node_start_pfn & ~(MAX_ORDER_NR_PAGES - 1);
+ offset = pgdat->node_start_pfn - start;
end = pgdat_end_pfn(pgdat);
end = ALIGN(end, MAX_ORDER_NR_PAGES);
size = (end - start) * sizeof(struct page);
@@ -4976,7 +4979,7 @@ static void __init_refok alloc_node_mem_map(struct pglist_data *pgdat)
if (!map)
map = memblock_virt_alloc_node_nopanic(size,
pgdat->node_id);
- pgdat->node_mem_map = map + (pgdat->node_start_pfn - start);
+ pgdat->node_mem_map = map + offset;
}
#ifndef CONFIG_NEED_MULTIPLE_NODES
/*
@@ -4984,9 +4987,9 @@ static void __init_refok alloc_node_mem_map(struct pglist_data *pgdat)
*/
if (pgdat == NODE_DATA(0)) {
mem_map = NODE_DATA(0)->node_mem_map;
-#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
+#if defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP) || defined(CONFIG_FLATMEM)
if (page_to_pfn(mem_map) != pgdat->node_start_pfn)
- mem_map -= (pgdat->node_start_pfn - ARCH_PFN_OFFSET);
+ mem_map -= offset;
#endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
}
#endif
--
2.4.3
--
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