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>

diff --git a/kernel/kexec.c b/kernel/kexec.c
index 20ed47ae252f12b32afff059e59c2a38bbbf0c44..60bf181b3eaed859dc7ae63f0338c01c4cfaed0d 100644 (file)
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -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: