From: "HORIGUCHI NAOYA(堀口 直也)" <naoya.horiguchi@nec.com>
To: Oscar Salvador <osalvador@suse.de>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>,
Muchun Song <songmuchun@bytedance.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Michal Hocko <mhocko@suse.com>, Tony Luck <tony.luck@intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 2/2] mm,hwpoison: make get_hwpoison_page call get_any_page()
Date: Thu, 13 May 2021 00:03:04 +0000 [thread overview]
Message-ID: <20210513000303.GB563308@hori.linux.bs1.fc.nec.co.jp> (raw)
In-Reply-To: <20210512085522.GB14726@linux>
On Wed, May 12, 2021 at 10:55:22AM +0200, Oscar Salvador wrote:
> On Wed, May 12, 2021 at 12:10:16AM +0900, Naoya Horiguchi wrote:
> > From: Naoya Horiguchi <naoya.horiguchi@nec.com>
> >
> > Now __get_hwpoison_page() could return -EBUSY in a race condition,
> > so it's helpful to handle it by retrying. We already have retry
> > logic, so make get_hwpoison_page() call get_any_page() when called
> > from memory_failure().
>
> As I stated in your previous patch, I think you should start returning -EBUSY
> from this patch onwards.
>
> > static int get_any_page(struct page *p, unsigned long flags)
> > {
> > int ret = 0, pass = 0;
> > @@ -1152,50 +1136,76 @@ static int get_any_page(struct page *p, unsigned long flags)
> > count_increased = true;
> >
> > try_again:
> > - if (!count_increased && !__get_hwpoison_page(p)) {
> > - if (page_count(p)) {
> > - /* We raced with an allocation, retry. */
> > - if (pass++ < 3)
> > - goto try_again;
> > - ret = -EBUSY;
> > - } else if (!PageHuge(p) && !is_free_buddy_page(p)) {
> > - /* We raced with put_page, retry. */
> > - if (pass++ < 3)
> > - goto try_again;
> > - ret = -EIO;
> > + if (!count_increased) {
> > + ret = __get_hwpoison_page(p);
> > + if (!ret) {
> > + if (page_count(p)) {
> > + /* We raced with an allocation, retry. */
> > + if (pass++ < 3)
> > + goto try_again;
> > + ret = -EBUSY;
> > + } else if (!PageHuge(p) && !is_free_buddy_page(p)) {
> > + /* We raced with put_page, retry. */
> > + if (pass++ < 3)
> > + goto try_again;
> > + ret = -EIO;
> > + }
> > + goto out;
> > }
> > + }
>
> I think this can be improved.
>
> We cannot have -EBUSY unless we come from __get_hwpoison_page() (!count_increased),
> so I think a much more natural approach would be to stuff the hunk below in there,
> and then place the other stuff in an else, so something like:
>
> if (!count_increased) {
> ret = __get_hwpoison_page(p);
> if (!ret) {
> if (page_count(p)) {
> /* We raced with an allocation, retry. */
> if (pass++ < 3)
> goto try_again;
> ret = -EBUSY;
> } else if (!PageHuge(p) && !is_free_buddy_page(p)) {
> /* We raced with put_page, retry. */
> if (pass++ < 3)
> goto try_again;
> ret = -EIO;
> }
> goto out;
> } else if (ret == -EBUSY) {
> /* We raced with freeing huge page to buddy, retry. */
> if (pass++ < 3)
> goto try_again;
> }
Moving "if (ret == -EBUSY)" block to here makes sense to me. Thank you.
> } else {
In the original logic, if __get_hwpoison_page() returns 1, we fall into the
"if (PageHuge(p) || PageLRU(p) || __PageMovable(p)" check. I guess that this
"else" seems not necessary?
> /* We do already have a refcount for this page, see if we can
> * handle it.
> */
> if (PageHuge(p) || PageLRU(p) || __PageMovable(p)) {
> ret = 1;
> } else {
> /* A page we cannot handle. Check...
> }
> }
Thanks,
Naoya Horiguchi
prev parent reply other threads:[~2021-05-13 0:03 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-11 15:10 [PATCH v3 0/2] hwpoison: fix race with compound page allocation Naoya Horiguchi
2021-05-11 15:10 ` [PATCH v3 1/2] mm,hwpoison: " Naoya Horiguchi
2021-05-12 8:33 ` Oscar Salvador
2021-05-13 0:00 ` HORIGUCHI NAOYA(堀口 直也)
2021-05-12 12:19 ` Michal Hocko
2021-05-12 23:51 ` HORIGUCHI NAOYA(堀口 直也)
2021-05-11 15:10 ` [PATCH v3 2/2] mm,hwpoison: make get_hwpoison_page call get_any_page() Naoya Horiguchi
2021-05-12 8:55 ` Oscar Salvador
2021-05-13 0:03 ` HORIGUCHI NAOYA(堀口 直也) [this message]
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