From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f173.google.com (mail-pd0-f173.google.com [209.85.192.173]) by kanga.kvack.org (Postfix) with ESMTP id 8891D6B0031 for ; Mon, 16 Jun 2014 09:41:29 -0400 (EDT) Received: by mail-pd0-f173.google.com with SMTP id r10so4450450pdi.32 for ; Mon, 16 Jun 2014 06:41:29 -0700 (PDT) Received: from mga09.intel.com (mga09.intel.com. [134.134.136.24]) by mx.google.com with ESMTP id yv3si13744280pac.77.2014.06.16.06.41.28 for ; Mon, 16 Jun 2014 06:41:28 -0700 (PDT) From: "Kirill A. Shutemov" In-Reply-To: <1402676778-27174-1-git-send-email-chris@chris-wilson.co.uk> References: <1402676778-27174-1-git-send-email-chris@chris-wilson.co.uk> Subject: RE: [PATCH 1/2] mm: Report attempts to overwrite PTE from remap_pfn_range() Content-Transfer-Encoding: 7bit Message-Id: <20140616134124.0ED73E00A2@blue.fi.intel.com> Date: Mon, 16 Jun 2014 16:41:24 +0300 (EEST) Sender: owner-linux-mm@kvack.org List-ID: To: Chris Wilson Cc: intel-gfx@lists.freedesktop.org, Andrew Morton , "Kirill A. Shutemov" , Peter Zijlstra , Rik van Riel , Mel Gorman , Cyrill Gorcunov , Johannes Weiner , linux-mm@kvack.org Chris Wilson wrote: > When using remap_pfn_range() from a fault handler, we are exposed to > races between concurrent faults. Rather than hitting a BUG, report the > error back to the caller, like vm_insert_pfn(). > > Signed-off-by: Chris Wilson > Cc: Andrew Morton > Cc: "Kirill A. Shutemov" > Cc: Peter Zijlstra > Cc: Rik van Riel > Cc: Mel Gorman > Cc: Cyrill Gorcunov > Cc: Johannes Weiner > Cc: linux-mm@kvack.org > --- > mm/memory.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index 037b812a9531..6603a9e6a731 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -2306,19 +2306,23 @@ static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd, > { > pte_t *pte; > spinlock_t *ptl; > + int ret = 0; > > pte = pte_alloc_map_lock(mm, pmd, addr, &ptl); > if (!pte) > return -ENOMEM; > arch_enter_lazy_mmu_mode(); > do { > - BUG_ON(!pte_none(*pte)); > + if (!pte_none(*pte)) { > + ret = -EBUSY; > + break; I think you need at least remove entries you've setup if the check failed not at first iteration. And nobody propagate your -EBUSY back to remap_pfn_range(): caller will see -ENOMEM, which is not what you want, I believe. -- Kirill A. Shutemov -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org