From: Hugh Dickins <hughd@google.com>
To: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
David Rientjes <rientjes@google.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Naoya Horiguchi <nao.horiguchi@gmail.com>,
stable@vger.kernel.org
Subject: Re: [PATCH v3 3/5] mm/hugetlb: fix getting refcount 0 page in hugetlb_fault()
Date: Mon, 29 Sep 2014 21:52:24 -0700 (PDT) [thread overview]
Message-ID: <alpine.LSU.2.11.1409292132370.4640@eggly.anvils> (raw)
In-Reply-To: <1410820799-27278-4-git-send-email-n-horiguchi@ah.jp.nec.com>
On Mon, 15 Sep 2014, Naoya Horiguchi wrote:
> When running the test which causes the race as shown in the previous patch,
> we can hit the BUG "get_page() on refcount 0 page" in hugetlb_fault().
Two minor comments...
> @@ -3192,22 +3208,19 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
> * Note that locking order is always pagecache_page -> page,
> * so no worry about deadlock.
That sentence of comment is stale and should be deleted,
now that you're only doing a trylock_page(page) here.
> out_mutex:
> mutex_unlock(&htlb_fault_mutex_table[hash]);
> + if (need_wait_lock)
> + wait_on_page_locked(page);
> return ret;
> }
It will be hard to trigger any problem from this (I guess it would
need memory hotremove), but you ought really to hold a reference to
page while doing a wait_on_page_locked(page).
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next prev parent reply other threads:[~2014-09-30 4:54 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-15 22:39 [PATCH 0/5] hugepage migration fixes (v4) Naoya Horiguchi
2014-09-15 22:39 ` [PATCH v3 1/5] mm/hugetlb: reduce arch dependent code around follow_huge_* Naoya Horiguchi
2014-09-16 15:56 ` Naoya Horiguchi
2014-09-15 22:39 ` [PATCH v3 2/5] mm/hugetlb: take page table lock in follow_huge_pmd() Naoya Horiguchi
2014-09-30 4:32 ` Hugh Dickins
2014-10-07 16:56 ` Naoya Horiguchi
2014-09-15 22:39 ` [PATCH v3 3/5] mm/hugetlb: fix getting refcount 0 page in hugetlb_fault() Naoya Horiguchi
2014-09-30 4:52 ` Hugh Dickins [this message]
2014-10-07 16:56 ` Naoya Horiguchi
2014-09-15 22:39 ` [PATCH v3 4/5] mm/hugetlb: add migration/hwpoisoned entry check in hugetlb_change_protection Naoya Horiguchi
2014-09-15 22:39 ` [PATCH v3 5/5] mm/hugetlb: add migration entry check in __unmap_hugepage_range Naoya Horiguchi
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