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Re: [PATCH v2] MIPS: Kernel crashes on boot with SPARSEMEM + HIGHMEM ena

To: Kevin Cernekee <cernekee@gmail.com>
Subject: Re: [PATCH v2] MIPS: Kernel crashes on boot with SPARSEMEM + HIGHMEM enabled
From: David Daney <ddaney@caviumnetworks.com>
Date: Fri, 01 Apr 2011 09:56:56 -0700
Cc: Ralf Baechle <ralf@linux-mips.org>, Michael Sundius <msundius@cisco.com>, David VomLehn <dvomlehn@cisco.com>, Dave Hansen <dave@linux.vnet.ibm.com>, Andy Whitcroft <apw@shadowen.org>, Jon Fraser <jfraser@broadcom.com>, linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, stable@kernel.org
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On 03/31/2011 05:27 PM, Kevin Cernekee wrote:
From: Michael Sundius<msundius@cisco.com>

Fix 3 problems in the MIPS SPARSEMEM implementation:

1) mem_init() sets/clears PG_reserved on all pages in the HIGHMEM range
without checking to see whether the page descriptor actually exists.

2) bootmem_init() never calls memory_present() on HIGHMEM pages, so
page descriptors are never created for them if SPARSEMEM is enabled.

3) bootmem_init() calls memory_present() on lowmem pages before bootmem
is fully set up.  This is bad because memory_present() can allocate
bootmem in some circumstances (e.g. if SPARSEMEM_EXTREME ever got
enabled).



I think this may do the same thing as my patch:

http://patchwork.linux-mips.org/patch/1988/

Although my patch had different motivations, and changes some other things around too.

David Daney


Signed-off-by: Michael Sundius<msundius@cisco.com>
Signed-off-by: Kevin Cernekee<cernekee@gmail.com>
Cc: stable@kernel.org
---
  arch/mips/kernel/setup.c |   18 +++++++++++++++++-
  arch/mips/mm/init.c      |    3 +++
  2 files changed, 20 insertions(+), 1 deletions(-)

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 8ad1d56..1f9f902 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -390,7 +390,6 @@ static void __init bootmem_init(void)

                /* Register lowmem ranges */
                free_bootmem(PFN_PHYS(start), size<<  PAGE_SHIFT);
-               memory_present(0, start, end);
        }

        /*
@@ -402,6 +401,23 @@ static void __init bootmem_init(void)
         * Reserve initrd memory if needed.
         */
        finalize_initrd();
+
+       /*
+        * Call memory_present() on all valid ranges, for SPARSEMEM.
+        * This must be done after setting up bootmem, since memory_present()
+        * may allocate bootmem.
+        */
+       for (i = 0; i<  boot_mem_map.nr_map; i++) {
+               unsigned long start, end;
+
+               if (boot_mem_map.map[i].type != BOOT_MEM_RAM)
+                       continue;
+
+               start = PFN_UP(boot_mem_map.map[i].addr);
+               end   = PFN_DOWN(boot_mem_map.map[i].addr
+                                   + boot_mem_map.map[i].size);
+               memory_present(0, start, end);
+       }
  }

  #endif        /* CONFIG_SGI_IP27 */
diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c
index 279599e..78a4cf2 100644
--- a/arch/mips/mm/init.c
+++ b/arch/mips/mm/init.c
@@ -392,6 +392,9 @@ void __init mem_init(void)
        for (tmp = highstart_pfn; tmp<  highend_pfn; tmp++) {
                struct page *page = pfn_to_page(tmp);

+               if (!pfn_valid(tmp))
+                       continue;
+
                if (!page_is_ram(tmp)) {
                        SetPageReserved(page);
                        continue;


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