Commit 6480e5a0 authored Jan 12, 2012 by Michael Holzheu Committed by Linus Torvalds Jan 12, 2012

kdump: add missing RAM resource in crash_shrink_memory()



When shrinking crashkernel memory using /sys/kernel/kexec_crash_size for
the newly added memory no RAM resource is created at the moment.

Example:

  $ cat /proc/iomem
  00000000-bfffffff : System RAM
    00000000-005b7ac3 : Kernel code
    005b7ac4-009743bf : Kernel data
    009bb000-00a85c33 : Kernel bss
  c0000000-cfffffff : Crash kernel
  d0000000-ffffffff : System RAM

  $ echo 0 > /sys/kernel/kexec_crash_size
  $ cat /proc/iomem
  00000000-bfffffff : System RAM
    00000000-005b7ac3 : Kernel code
    005b7ac4-009743bf : Kernel data
    009bb000-00a85c33 : Kernel bss
                                   <<-- here is System RAM missing
  d0000000-ffffffff : System RAM

One result of this bug is that the memory chunk can never be set offline
using memory hotplug.  With this patch I insert a new "System RAM"
resource for the released memory.  Then the upper example looks like the
following:

  $ echo 0 > /sys/kernel/kexec_crash_size
  $ cat /proc/iomem
  00000000-bfffffff : System RAM
    00000000-005b7ac3 : Kernel code
    005b7ac4-009743bf : Kernel data
    009bb000-00a85c33 : Kernel bss
  c0000000-cfffffff : System RAM   <<-- new rescoure
  d0000000-ffffffff : System RAM

And now I can set chunk c0000000-cfffffff offline.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent a3dd3323

kernel/kexec.c

+15 −0

Original line number	Diff line number	Diff line
		@@ -1129,6 +1129,7 @@ int crash_shrink_memory(unsigned long new_size)
		{
		int ret = 0;
		unsigned long start, end;
		struct resource *ram_res;

		mutex_lock(&kexec_mutex);

		@@ -1146,6 +1147,12 @@ int crash_shrink_memory(unsigned long new_size)
		goto unlock;
		}

		ram_res = kzalloc(sizeof(*ram_res), GFP_KERNEL);
		if (!ram_res) {
		ret = -ENOMEM;
		goto unlock;
		}

		start = roundup(start, KEXEC_CRASH_MEM_ALIGN);
		end = roundup(start + new_size, KEXEC_CRASH_MEM_ALIGN);

		@@ -1154,7 +1161,15 @@ int crash_shrink_memory(unsigned long new_size)

		if ((start == end) && (crashk_res.parent != NULL))
		release_resource(&crashk_res);

		ram_res->start = end;
		ram_res->end = crashk_res.end;
		ram_res->flags = IORESOURCE_BUSY \| IORESOURCE_MEM;
		ram_res->name = "System RAM";

		crashk_res.end = end - 1;

		insert_resource(&iomem_resource, ram_res);
		crash_unmap_reserved_pages();

		unlock: