Commit c6c40533 authored by Kairui Song's avatar Kairui Song Committed by Linus Torvalds
Browse files

vmcore: add a kernel parameter novmcoredd 

Since commit 2724273e ("vmcore: add API to collect hardware dump in
second kernel"), drivers are allowed to add device related dump data to
vmcore as they want by using the device dump API.  This has a potential
issue, the data is stored in memory, drivers may append too much data
and use too much memory.  The vmcore is typically used in a kdump kernel
which runs in a pre-reserved small chunk of memory.  So as a result it
will make kdump unusable at all due to OOM issues.

So introduce new 'novmcoredd' command line option.  User can disable
device dump to reduce memory usage.  This is helpful if device dump is
using too much memory, disabling device dump could make sure a regular
vmcore without device dump data is still available.

[akpm@linux-foundation.org: tweak documentation]
[akpm@linux-foundation.org: vmcore.c needs moduleparam.h]
Link: http://lkml.kernel.org/r/20190528111856.7276-1-kasong@redhat.com


Signed-off-by: default avatarKairui Song <kasong@redhat.com>
Acked-by: default avatarDave Young <dyoung@redhat.com>
Reviewed-by: default avatarBhupesh Sharma <bhsharma@redhat.com>
Cc: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Cc: "David S . Miller" <davem@davemloft.net>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent bca1eac5

Documentation/admin-guide/kernel-parameters.txt

+11 −0
Original line number Diff line number Diff line
@@ -2877,6 +2877,17 @@ 
			/sys/module/printk/parameters/console_suspend) to

			turn on/off it dynamically.



	novmcoredd	[KNL,KDUMP]

			Disable device dump. Device dump allows drivers to

			append dump data to vmcore so you can collect driver

			specified debug info.  Drivers can append the data

			without any limit and this data is stored in memory,

			so this may cause significant memory stress.  Disabling

			device dump can help save memory but the driver debug

			data will be no longer available.  This parameter

			is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP

			is set.



	noaliencache	[MM, NUMA, SLAB] Disables the allocation of alien

			caches in the slab allocator.  Saves per-node memory,

			but will impact performance.

fs/proc/Kconfig

+2 −1
Original line number Diff line number Diff line
@@ -58,7 +58,8 @@ config PROC_VMCORE_DEVICE_DUMP 
	  snapshot.



	  If you say Y here, the collected device dumps will be added

	  as ELF notes to /proc/vmcore.

	  as ELF notes to /proc/vmcore. You can still disable device

	  dump using the kernel command line option 'novmcoredd'.



config PROC_SYSCTL

	bool "Sysctl support (/proc/sys)" if EXPERT

fs/proc/vmcore.c

+9 −0
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 
#include <linux/init.h>

#include <linux/crash_dump.h>

#include <linux/list.h>

#include <linux/moduleparam.h>

#include <linux/mutex.h>

#include <linux/vmalloc.h>

#include <linux/pagemap.h>
@@ -54,6 +55,9 @@ static struct proc_dir_entry *proc_vmcore; 
/* Device Dump list and mutex to synchronize access to list */

static LIST_HEAD(vmcoredd_list);

static DEFINE_MUTEX(vmcoredd_mutex);



static bool vmcoredd_disabled;

core_param(novmcoredd, vmcoredd_disabled, bool, 0);

#endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */



/* Device Dump Size */
@@ -1452,6 +1456,11 @@ int vmcore_add_device_dump(struct vmcoredd_data *data) 
	size_t data_size;

	int ret;



	if (vmcoredd_disabled) {

		pr_err_once("Device dump is disabled\n");

		return -EINVAL;

	}



	if (!data || !strlen(data->dump_name) ||

	    !data->vmcoredd_callback || !data->size)

		return -EINVAL;

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