Hi Russell,
By reading the code of show_mem(), I found that there is an assumption
that the page structs must be continuous for each bank:
for_each_bank (i, mi) {
...
page = pfn_to_page(pfn1);
end = pfn_to_page(pfn2 - 1) + 1;
do {
...
page++; <-- pageframe must be continuous
...
} while (page < end);
...
}
Therefore, a bank must be fully contained in a section in sparse memory
mode, because page frames are allocated section by section (in
sparse_init()).
However, I didn't find other code which enforces this assumption.
Instead, in arm_memory_present (arch/arm/mm/init.c), it seems that a
bank may contain more than one section:
arm_memory_present:
...
for_each_memblock(memory, reg)
memory_present(0, memblock_region_memory_base_pfn(reg),
memblock_region_memory_end_pfn(reg));
...
memory_present:
...
for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) {
...
}
...
Therefore, would you please consider the following patch, which removes
the assumption that a bank must be fully contained in one section?
===========================
>From b2c4bb5807c755d92274e11bb00cc548fea62242 Mon Sep 17 00:00:00 2001
From: Wang Nan <wangn...@huawei.com>
Date: Thu, 2 Jan 2014 13:20:02 +0800
Subject: [PATCH] use pfn_to_page in show_mem
If a bank spans into different sections, the page structures of the bank
may not continous.
This patch uses pfn_to_page to recompute the address of struct page in show_mem
from pfn, makes it to collect correct information even if a bank spans into
different sections.
Signed-off-by: Wang Nan <wangn...@huawei.com>
---
arch/arm/mm/init.c | 16 +++++++---------
1 file changed, 7 insertions(+), 9 deletions(-)
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 1f7b19a..3078e5a 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -97,16 +97,14 @@ void show_mem(unsigned int filter)
for_each_bank (i, mi) {
struct membank *bank = &mi->bank[i];
- unsigned int pfn1, pfn2;
- struct page *page, *end;
+ unsigned int pfn, pfn_end;
+ struct page *page;
- pfn1 = bank_pfn_start(bank);
- pfn2 = bank_pfn_end(bank);
-
- page = pfn_to_page(pfn1);
- end = pfn_to_page(pfn2 - 1) + 1;
+ pfn = bank_pfn_start(bank);
+ pfn_end = bank_pfn_end(bank);
do {
+ page = pfn_to_page(pfn);
total++;
if (PageReserved(page))
reserved++;
@@ -118,8 +116,8 @@ void show_mem(unsigned int filter)
free++;
else
shared += page_count(page) - 1;
- page++;
- } while (page < end);
+ pfn++;
+ } while (pfn < pfn_end);
}
printk("%d pages of RAM\n", total);
--
1.8.4
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