linux-kernel - [PATCH] kexec: Account crashk_low_res to kexec_crash

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Date:	Sat, 13 Aug 2016 16:26:10 +0800
From:	Xunlei Pang <xlpang@...hat.com>
To:	linux-kernel@...r.kernel.org, kexec@...ts.infradead.org
Cc:	akpm@...ux-foundation.org, ebiederm@...ssion.com,
	Vivek Goyal <vgoyal@...hat.com>,
	Dave Young <dyoung@...hat.com>, Baoquan He <bhe@...hat.com>,
	Xunlei Pang <xlpang@...hat.com>
Subject: [PATCH] kexec: Account crashk_low_res to kexec_crash_size

"/sys/kernel/kexec_crash_size" only includes crashk_res, it
is fine in most cases, but sometimes we have crashk_low_res.
For example, when "crashkernel=size[KMG],high" combined with
"crashkernel=size[KMG],low" is used for 64-bit x86.

Let "/sys/kernel/kexec_crash_size" reflect all the reserved
memory including crashk_low_res, this is more understandable
from its naming.

Although we can get all the crash memory from "/proc/iomem"
by filtering all "Crash kernel" keyword, it is more convenient
to utilize this file, and the two ways should stay consistent.

Note that write to "/sys/kernel/kexec_crash_size" is to shrink
the reserved memory, and we want to shrink crashk_res only.
So we add some additional check in crash_shrink_memory() since
crashk_low_res now is involved.

Signed-off-by: Xunlei Pang <xlpang@...hat.com>
---
 kernel/kexec_core.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 5616755..d5ae780 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -932,6 +932,8 @@ size_t crash_get_memory_size(void)
 	mutex_lock(&kexec_mutex);
 	if (crashk_res.end != crashk_res.start)
 		size = resource_size(&crashk_res);
+	if (crashk_low_res.end != crashk_low_res.start)
+		size += resource_size(&crashk_low_res);
 	mutex_unlock(&kexec_mutex);
 	return size;
 }
@@ -949,7 +951,7 @@ int crash_shrink_memory(unsigned long new_size)
 {
 	int ret = 0;
 	unsigned long start, end;
-	unsigned long old_size;
+	unsigned long low_size, old_size;
 	struct resource *ram_res;

 	mutex_lock(&kexec_mutex);
@@ -958,6 +960,17 @@ int crash_shrink_memory(unsigned long new_size)
 		ret = -ENOENT;
 		goto unlock;
 	}
+
+	start = crashk_low_res.start;
+	end = crashk_low_res.end;
+	low_size = (end == 0) ? 0 : end - start + 1;
+	/* Do not shrink crashk_low_res. */
+	if (new_size <= low_size) {
+		ret = -EINVAL;
+		goto unlock;
+	}
+
+	new_size -= low_size;
 	start = crashk_res.start;
 	end = crashk_res.end;
 	old_size = (end == 0) ? 0 : end - start + 1;
-- 
1.8.3.1