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Thu, 26 Sep 2019 02:10:51 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x8Q29JAX078297; Thu, 26 Sep 2019 02:10:50 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by aserp3030.oracle.com with ESMTP id 2v82tm48c2-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 26 Sep 2019 02:10:50 +0000 Received: from abhmp0015.oracle.com (abhmp0015.oracle.com [141.146.116.21]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x8Q2Aleq002932; Thu, 26 Sep 2019 02:10:48 GMT Received: from [192.168.1.222] (/71.63.128.209) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 25 Sep 2019 19:10:47 -0700 Subject: Re: [PATCH 1/2] userfaultfd: remove one unnecessary warn_on in __mcopy_atomic_hugetlb To: Wei Yang Cc: akpm@linux-foundation.org, aarcange@redhat.com, hughd@google.com, linux-mm@kvack.org References: <20190925121833.2766-1-richardw.yang@linux.intel.com> <3f69dc19-eb3b-ed46-62bc-c5e6e89ab6eb@oracle.com> <20190926003528.GA3162@richard> From: Mike Kravetz Message-ID: <89ab9534-33c6-523c-bef0-282826af1be5@oracle.com> Date: Wed, 25 Sep 2019 19:10:46 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190926003528.GA3162@richard> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9391 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1909260023 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9391 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1909260023 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 9/25/19 5:35 PM, Wei Yang wrote: > On Wed, Sep 25, 2019 at 10:44:58AM -0700, Mike Kravetz wrote: >> On 9/25/19 5:18 AM, Wei Yang wrote: >>> The warning here is to make sure address(dst_addr) and length(len - >>> copied) are huge page size aligned. >>> >>> While this is ensured by: >>> >>> dst_start and len is huge page size aligned >>> dst_addr equals to dst_start and increase huge page size each time >>> copied increase huge page size each time >> >> Can we also remove the following for the same reasons? >> >> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c >> index 640ff2bd9a69..f82d5ec698d8 100644 >> --- a/mm/userfaultfd.c >> +++ b/mm/userfaultfd.c >> @@ -262,7 +262,6 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm, >> pte_t dst_pteval; >> >> BUG_ON(dst_addr >= dst_start + len); >> - VM_BUG_ON(dst_addr & ~huge_page_mask(h)); >> > > Thanks for your comment. > > It looks good, while I lack some knowledge between vma_hpagesize and > huge_page_mask(). vma_hpagesize is just a local variable used so that repeated calls to vma_kernel_pagesize() or huge_page_size() are not necessary. > If they are the same, why not use the same interface for all those checks in > this function? If we remove the VM_BUG_ON, that is the only use of huge_page_mask() in the function. We can can also eliminate a call to huge_page_size() by making this change. @@ -273,7 +272,7 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm, mutex_lock(&hugetlb_fault_mutex_table[hash]); err = -ENOMEM; - dst_pte = huge_pte_alloc(dst_mm, dst_addr, huge_page_size(h)); + dst_pte = huge_pte_alloc(dst_mm, dst_addr, vma_hpagesize); if (!dst_pte) { mutex_unlock(&hugetlb_fault_mutex_table[hash]); goto out_unlock; -- Mike Kravetz