On Tue, May 28, 2019 at 4:52 PM Kairui Song <kasong@xxxxxxxxxx> wrote:
>
> Since commit 2724273e8fd0 ("vmcore: add API to collect hardware dump in
> second kernel"), drivers is allowed to add device related dump data to
> vmcore as they want by using the device dump API. This have 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.
>
> Signed-off-by: Kairui Song <kasong@xxxxxxxxxx>
>
> ---
> Update from V3:
> - Use novmcoredd instead of vmcore_device_dump. Use
> vmcore_device_dump and make it off by default is confusing,
> novmcoredd is a cleaner way to let user space be able to disable
> device dump to save memory.
>
> Update from V2:
> - Improve related docs
>
> Update from V1:
> - Use bool parameter to turn it on/off instead of letting user give
> the size limit. Size of device dump is hard to determine.
>
> Documentation/admin-guide/kernel-parameters.txt | 11 +++++++++++
> fs/proc/Kconfig | 3 ++-
> fs/proc/vmcore.c | 8 ++++++++
> 3 files changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 138f6664b2e2..1b900d262680 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2872,6 +2872,17 @@
> /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. The drivers could append the
> + data without any limit, and the data is stored in
> + memory, this may bring a significant memory stress.
> + Disable device dump can help save memory but driver
> + debug data will be no longer available.
> + 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.
> diff --git a/fs/proc/Kconfig b/fs/proc/Kconfig
> index 817c02b13b1d..62b19162d198 100644
> --- a/fs/proc/Kconfig
> +++ b/fs/proc/Kconfig
> @@ -57,7 +57,8 @@ 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 disabled device
> + dump by command line option 'novmcoredd'.
>
> config PROC_SYSCTL
> bool "Sysctl support (/proc/sys)" if EXPERT
> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
> index 3fe90443c1bb..e815fd035fc0 100644
> --- a/fs/proc/vmcore.c
> +++ b/fs/proc/vmcore.c
> @@ -53,6 +53,9 @@ 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 */
> @@ -1451,6 +1454,11 @@ 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;
> --
> 2.21.0
LGTM, so:
Reviewed-by: Bhupesh Sharma <bhsharma@xxxxxxxxxx>
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