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Subject[PATCH] kdump: Add missing RAM resource in crash_shrink_memory()
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From: Michael Holzheu <holzheu@linux.vnet.ibm.com>

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>
---
kernel/kexec.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)

--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -1132,6 +1132,7 @@ int crash_shrink_memory(unsigned long ne
{
int ret = 0;
unsigned long start, end;
+ struct resource *ram_res;

mutex_lock(&kexec_mutex);

@@ -1149,6 +1150,12 @@ int crash_shrink_memory(unsigned long ne
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);

@@ -1157,7 +1164,15 @@ int crash_shrink_memory(unsigned long ne

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:



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