On Tue, Jun 14, 2022 at 12:38:29PM +0800, zhenwei pi wrote:
> Add a new debug entry to show the number of hwpoisoned pages. And
> use module_get/module_put to manager this kernel module, don't allow
> to remove this module unless hwpoisoned-pages is zero.
>
> Signed-off-by: zhenwei pi <pizhenwei@xxxxxxxxxxxxx>
> ---
> Documentation/vm/hwpoison.rst | 4 ++++
> mm/hwpoison-inject.c | 19 ++++++++++++++++++-
> 2 files changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/vm/hwpoison.rst b/Documentation/vm/hwpoison.rst
> index c742de1769d1..c832a8b192d4 100644
> --- a/Documentation/vm/hwpoison.rst
> +++ b/Documentation/vm/hwpoison.rst
> @@ -155,6 +155,10 @@ Testing
> flag bits are defined in include/linux/kernel-page-flags.h and
> documented in Documentation/admin-guide/mm/pagemap.rst
>
> + hwpoisoned-pages
> + The number of hwpoisoned pages. The hwpoison kernel module can not be
> + removed unless this count is zero.
> +
> * Architecture specific MCE injector
>
> x86 has mce-inject, mce-test
> diff --git a/mm/hwpoison-inject.c b/mm/hwpoison-inject.c
> index 5c0cddd81505..9e522ecedeef 100644
> --- a/mm/hwpoison-inject.c
> +++ b/mm/hwpoison-inject.c
> @@ -10,6 +10,7 @@
> #include "internal.h"
>
> static struct dentry *hwpoison_dir;
> +static atomic_t hwpoisoned_pages;
>
> static int hwpoison_inject(void *data, u64 val)
> {
> @@ -49,15 +50,28 @@ static int hwpoison_inject(void *data, u64 val)
> inject:
> pr_info("Injecting memory failure at pfn %#lx\n", pfn);
> err = memory_failure(pfn, 0);
> + if (!err) {
> + WARN_ON(!try_module_get(THIS_MODULE));
> + atomic_inc(&hwpoisoned_pages);
> + }
There's a few other interfaces to generate "software-simulated memory error"
event, i.e. madvise_inject_error() and hard_offline_page_store(). So you need
handle such code path.
> +
> return (err == -EOPNOTSUPP) ? 0 : err;
> }
>
> static int hwpoison_unpoison(void *data, u64 val)
> {
> + int ret;
> +
> if (!capable(CAP_SYS_ADMIN))
> return -EPERM;
>
> - return unpoison_memory(val);
> + ret = unpoison_memory(val);
> + if (!ret) {
> + atomic_dec(&hwpoisoned_pages);
> + module_put(THIS_MODULE);
> + }
> +
> + return ret;
> }
>
> DEFINE_DEBUGFS_ATTRIBUTE(hwpoison_fops, NULL, hwpoison_inject, "%lli\n");
> @@ -99,6 +113,9 @@ static int pfn_inject_init(void)
> debugfs_create_u64("corrupt-filter-flags-value", 0600, hwpoison_dir,
> &hwpoison_filter_flags_value);
>
> + debugfs_create_atomic_t("hwpoisoned-pages", 0400, hwpoison_dir,
> + &hwpoisoned_pages);
I'm not sure how useful this interface from userspace (controlling test process
with this?). Do we really need to expose this to userspace?
TBH I feel that another approach like below is more desirable:
- define a new flag in "enum mf_flags" (for example named MF_SW_SIMULATED),
- set the flag when calling memory_failure() from the three callers
mentioned above,
- define a global variable (typed bool) in mm/memory_failure.c_to show that
the system has experienced a real hardware memory error events.
- once memory_failure() is called without MF_SW_SIMULATED, the new global
bool variable is set, and afterward unpoison_memory always fails with
-EOPNOTSUPP.
Thanks,
Naoya Horiguchi
