x86/mm/hotplug: Modify PGD entry when removing memory
When hot-adding/removing memory, sync_global_pgds() is called
for synchronizing PGD to PGD entries of all processes MM. But
when hot-removing memory, sync_global_pgds() does not work
correctly.
At first, sync_global_pgds() checks whether target PGD is none
or not. And if PGD is none, the PGD is skipped. But when
hot-removing memory, PGD may be none since PGD may be cleared by
free_pud_table(). So when sync_global_pgds() is called after
hot-removing memory, sync_global_pgds() should not skip PGD even
if the PGD is none. And sync_global_pgds() must clear PGD
entries of all processes MM.
Currently sync_global_pgds() does not clear PGD entries of all
processes MM when hot-removing memory. So when hot adding
memory which is same memory range as removed memory after
hot-removing memory, following call traces are shown:
kernel BUG at arch/x86/mm/init_64.c:206!
...
[<ffffffff815e0c80>] kernel_physical_mapping_init+0x1b2/0x1d2
[<ffffffff815ced94>] init_memory_mapping+0x1d4/0x380
[<ffffffff8104aebd>] arch_add_memory+0x3d/0xd0
[<ffffffff815d03d9>] add_memory+0xb9/0x1b0
[<ffffffff81352415>] acpi_memory_device_add+0x1af/0x28e
[<ffffffff81325dc4>] acpi_bus_device_attach+0x8c/0xf0
[<ffffffff813413b9>] acpi_ns_walk_namespace+0xc8/0x17f
[<ffffffff81325d38>] ? acpi_bus_type_and_status+0xb7/0xb7
[<ffffffff81325d38>] ? acpi_bus_type_and_status+0xb7/0xb7
[<ffffffff813418ed>] acpi_walk_namespace+0x95/0xc5
[<ffffffff81326b4c>] acpi_bus_scan+0x9a/0xc2
[<ffffffff81326bff>] acpi_scan_bus_device_check+0x8b/0x12e
[<ffffffff81326cb5>] acpi_scan_device_check+0x13/0x15
[<ffffffff81320122>] acpi_os_execute_deferred+0x25/0x32
[<ffffffff8107e02b>] process_one_work+0x17b/0x460
[<ffffffff8107edfb>] worker_thread+0x11b/0x400
[<ffffffff8107ece0>] ? rescuer_thread+0x400/0x400
[<ffffffff81085aef>] kthread+0xcf/0xe0
[<ffffffff81085a20>] ? kthread_create_on_node+0x140/0x140
[<ffffffff815fc76c>] ret_from_fork+0x7c/0xb0
[<ffffffff81085a20>] ? kthread_create_on_node+0x140/0x140
This patch clears PGD entries of all processes MM when
sync_global_pgds() is called after hot-removing memory
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Tang Chen <tangchen@cn.fujitsu.com>
Cc: Gu Zheng <guz.fnst@cn.fujitsu.com>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 0e996c0..52962511 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -178,7 +178,7 @@
* When memory was added/removed make sure all the processes MM have
* suitable PGD entries in the local PGD level page.
*/
-void sync_global_pgds(unsigned long start, unsigned long end)
+void sync_global_pgds(unsigned long start, unsigned long end, int removed)
{
unsigned long address;
@@ -186,7 +186,12 @@
const pgd_t *pgd_ref = pgd_offset_k(address);
struct page *page;
- if (pgd_none(*pgd_ref))
+ /*
+ * When it is called after memory hot remove, pgd_none()
+ * returns true. In this case (removed == 1), we must clear
+ * the PGD entries in the local PGD level page.
+ */
+ if (pgd_none(*pgd_ref) && !removed)
continue;
spin_lock(&pgd_lock);
@@ -199,12 +204,18 @@
pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
spin_lock(pgt_lock);
- if (pgd_none(*pgd))
- set_pgd(pgd, *pgd_ref);
- else
+ if (!pgd_none(*pgd_ref) && !pgd_none(*pgd))
BUG_ON(pgd_page_vaddr(*pgd)
!= pgd_page_vaddr(*pgd_ref));
+ if (removed) {
+ if (pgd_none(*pgd_ref) && !pgd_none(*pgd))
+ pgd_clear(pgd);
+ } else {
+ if (pgd_none(*pgd))
+ set_pgd(pgd, *pgd_ref);
+ }
+
spin_unlock(pgt_lock);
}
spin_unlock(&pgd_lock);
@@ -633,7 +644,7 @@
}
if (pgd_changed)
- sync_global_pgds(addr, end - 1);
+ sync_global_pgds(addr, end - 1, 0);
__flush_tlb_all();
@@ -995,7 +1006,7 @@
}
if (pgd_changed)
- sync_global_pgds(start, end - 1);
+ sync_global_pgds(start, end - 1, 1);
flush_tlb_all();
}
@@ -1342,7 +1353,7 @@
else
err = vmemmap_populate_basepages(start, end, node);
if (!err)
- sync_global_pgds(start, end - 1);
+ sync_global_pgds(start, end - 1, 0);
return err;
}