Messages in this thread | | | Date | Mon, 30 Nov 2015 14:10:16 -0800 (PST) | From | David Rientjes <> | Subject | Re: [PATCH v1] mm: hugetlb: call huge_pte_alloc() only if ptep is null |
| |
On Thu, 26 Nov 2015, Naoya Horiguchi wrote:
> Currently at the beginning of hugetlb_fault(), we call huge_pte_offset() > and check whether the obtained *ptep is a migration/hwpoison entry or not. > And if not, then we get to call huge_pte_alloc(). This is racy because the > *ptep could turn into migration/hwpoison entry after the huge_pte_offset() > check. This race results in BUG_ON in huge_pte_alloc(). > > We don't have to call huge_pte_alloc() when the huge_pte_offset() returns > non-NULL, so let's fix this bug with moving the code into else block. > > Note that the *ptep could turn into a migration/hwpoison entry after > this block, but that's not a problem because we have another !pte_present > check later (we never go into hugetlb_no_page() in that case.) > > Fixes: 290408d4a250 ("hugetlb: hugepage migration core") > Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> > Cc: <stable@vger.kernel.org> [2.6.36+]
Acked-by: David Rientjes <rientjes@google.com>
It would be nice to provide a sample of the BUG_ON() output in the commit message, however, so people can quickly find this if greping for what they just saw kill their machine.
| |