Re: [PATCH -mm v9 2/8] hwpoison: use page_cgroup_ino for filtering by memcg

Vladimir Davydov
2015-07-22T09:45:04Z

On Tue, Jul 21, 2015 at 04:34:12PM -0700, Andrew Morton wrote:
> On Sun, 19 Jul 2015 15:31:11 +0300 Vladimir Davydov <vdavydov-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org> wrote:
>
> > Hwpoison allows to filter pages by memory cgroup ino. Currently, it
> > calls try_get_mem_cgroup_from_page to obtain the cgroup from a page and
> > then its ino using cgroup_ino, but now we have an apter method for that,
> > page_cgroup_ino, so use it instead.
>
> I assume "an apter" was supposed to be "a helper"?

Yes, sounds better :-)

>
> > --- a/mm/hwpoison-inject.c
> > +++ b/mm/hwpoison-inject.c
> > @@ -45,12 +45,9 @@ static int hwpoison_inject(void *data, u64 val)
> > /*
> > * do a racy check with elevated page count, to make sure PG_hwpoison
> > * will only be set for the targeted owner (or on a free page).
> > - * We temporarily take page lock for try_get_mem_cgroup_from_page().
> > * memory_failure() will redo the check reliably inside page lock.
> > */
> > - lock_page(hpage);
> > err = hwpoison_filter(hpage);
> > - unlock_page(hpage);
> > if (err)
> > goto put_out;
> >
> > @@ -126,7 +123,7 @@ static int pfn_inject_init(void)
> > if (!dentry)
> > goto fail;
> >
> > -#ifdef CONFIG_MEMCG_SWAP
> > +#ifdef CONFIG_MEMCG
> > dentry = debugfs_create_u64("corrupt-filter-memcg", 0600,
> > hwpoison_dir, &hwpoison_filter_memcg);
> > if (!dentry)
>
> Confused. We're changing the conditions under which this debugfs file
> is created. Is this a typo or some unchangelogged thing or what?

This is an unchangelogged cleanup. In fact, there had been a comment
regarding it before v6, but then it got lost. Sorry about that. The
commit message should look like this:

"""
Hwpoison allows to filter pages by memory cgroup ino. Currently, it
calls try_get_mem_cgroup_from_page to obtain the cgroup from a page and
then its ino using cgroup_ino, but now we have a helper method for that,
page_cgroup_ino, so use it instead.

This patch also loosens the hwpoison memcg filter dependency rules - it
makes it depend on CONFIG_MEMCG instead of CONFIG_MEMCG_SWAP, because
hwpoison memcg filter does not require anything (nor it used to) from
CONFIG_MEMCG_SWAP side.
"""

Or we can simply revert this cleanups if you don't like it:
---
diff --git a/mm/hwpoison-inject.c b/mm/hwpoison-inject.c
index 5015679014c1..1cd105ee5a7b 100644
--- a/mm/hwpoison-inject.c
+++ b/mm/hwpoison-inject.c
@@ -123,7 +123,7 @@ static int pfn_inject_init(void)
if (!dentry)
goto fail;

-#ifdef CONFIG_MEMCG
+#ifdef CONFIG_MEMCG_SWAP
dentry = debugfs_create_u64("corrupt-filter-memcg", 0600,
hwpoison_dir, &hwpoison_filter_memcg);
if (!dentry)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 97005396a507..5ea7d8c760fa 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -130,7 +130,7 @@ static int hwpoison_filter_flags(struct page *p)
* can only guarantee that the page either belongs to the memcg tasks, or is
* a freed page.
*/
-#ifdef CONFIG_MEMCG
+#ifdef CONFIG_MEMCG_SWAP
u64 hwpoison_filter_memcg;
EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
static int hwpoison_filter_task(struct page *p)