Re: [PATCH v2 3/8] crash_core: change parse_crashkernel() to support crashkernel=,high|low parsing

On 08/31/23 at 10:56am, Leizhen (ThunderTown) wrote:

On 2023/8/29 20:16, Baoquan He wrote:

quoted

Now parse_crashkernel() is a real entry point for all kinds of
crahskernel parsing on any architecture.

And wrap the crahskernel=,high|low handling inside
CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION ifdeffery scope.

Signed-off-by: Baoquan He <redacted>
---
 include/linux/crash_core.h |  6 ++++++
 kernel/crash_core.c        | 28 +++++++++++++++++++++++++++-
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index 2e76289699ff..85260bf4a734 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h

@@ -77,6 +77,12 @@ Elf_Word *append_elf_note(Elf_Word *buf, char *name, unsigned int type,
 			  void *data, size_t data_len);
 void final_note(Elf_Word *buf);
 
+#ifdef CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
+#ifndef DEFAULT_CRASH_KERNEL_LOW_SIZE
+#define DEFAULT_CRASH_KERNEL_LOW_SIZE  (128UL << 20)
+#endif
+#endif
+
 int __init parse_crashkernel(char *cmdline, unsigned long long system_ram,
 		unsigned long long *crash_size, unsigned long long *crash_base,
 		unsigned long long *low_size, bool *high);

diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index f6a5c219e2e1..355b0ab5189c 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c

@@ -276,6 +276,9 @@ static int __init __parse_crashkernel(char *cmdline,
 /*
  * That function is the entry point for command line parsing and should be
  * called from the arch-specific code.
+ *
+ * If crashkernel=,high|low is supported on architecture, non-NULL values
+ * should be passed to parameters 'low_size' and 'high'.
  */
 int __init parse_crashkernel(char *cmdline,
 			     unsigned long long system_ram,

@@ -291,7 +294,30 @@ int __init parse_crashkernel(char *cmdline,
 				crash_base, NULL);
 	if (!high)
 		return ret;
-
+#ifdef CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
+	else if (ret == -ENOENT) {
+		ret = __parse_crashkernel(cmdline, 0, crash_size,
+				crash_base, suffix_tbl[SUFFIX_HIGH]);
+		if (ret || !*crash_size)
+			return -1;

Change -1 to -EINVAL?

Thanks a lot for careful reviewing, Zhen Lei.

Here, it's fine to me, parse_crashkernel() returns 0 on success, other value
on failure. '-1' or '-EINVAL' is not different to me in this case. I can
update if you think '-EINVAL' is better.

quoted

+
+		/*
+		 * crashkernel=Y,low can be specified or not, but invalid value
+		 * is not allowed.
+		 */
+		ret = __parse_crashkernel(cmdline, 0, low_size,
+				crash_base, suffix_tbl[SUFFIX_LOW]);
+		if (ret == -ENOENT)
+			*low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
+		else if (ret)
+			return -1;

return ret;

Ditto.

quoted

+
+		*high = true;
+	} else if (ret || !*crash_size) {

This check can be moved outside of #ifdef. Because even '!high', it's completely
applicable. The overall adjustment is as follows:

Hmm, the current logic is much easier to understand. However, I may not
100% get your suggestion. Can you paste the complete code in your
suggested way? Do not need 100% correct code, just the skeleton of code logic
so that I can better understand it and add inline comment.

-  	if (!high)
-  		return ret;

#ifdef CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
	if (high && ret == -ENOENT) {
		... ...
		if (ret || !*crash_size)	//parse HIGH
		... ...
	}

	//At this point, *crash_size is not 0 and ret is 0.
	//We can also delete if (!*crash_size) above because it will be checked later.
#endif

	if (!*crash_size)
		ret = -EINVAL;

	return ret;

When crashkernel=,high is specified while crashkernel=,low is omitted,
the ret==-ENOENT, but we can't return ret directly. That is still an
acceptable way.

-  	return 0;

quoted

+		/* The specified value is invalid */
+		return -1;
+	}
+#endif
 	return 0;
 }
 

-- 
Regards,
  Zhen Lei

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