From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELsC3oi0aDlLOH7PyfZwKo2A8A3Z7cU12Bo5rvZwdT9D5o5vqpmpFPnS/Li8fiJAEC0cnP38 ARC-Seal: i=1; a=rsa-sha256; t=1521192535; cv=none; d=google.com; s=arc-20160816; b=Zx5Zgo6akmRAHh1JDccSy0IFJ+y2PF6fzUQO6EFMjTzrgz0vp4xeZ5bEodtWOTmkOS +6cAamouSD0qN5TxLStyjNrpw8BlbTdQjviSiRkpxPEzPaxYL8Niq8kX72DwieKc/d7V 4vFeJn4WB4nHTyq2urh91AMHm50QMa4XsuWYL/CblN8YntfE0zE5hMbRSfX2R/y+2eFQ fmvWb70pkKaGb6wfJT+M6GpzYRoWZazIPr035AXE5Fdze3qToKK0JrP2l2MRJA0WkNLV bkpVT1W8zNAHLgD2BOaV02L4QBShjuB8nz3ZHqh+5g58ZP64aWKQx1fuiV66WEXsRJcu yLyA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=message-id:content-language:content-transfer-encoding:in-reply-to :mime-version:user-agent:date:from:references:cc:to:subject :arc-authentication-results; bh=CF2deXUZQC4hVmLH6Om+jCxiSMS+ZbH8zAyKqPJZ1ww=; b=NT4A720Aqm+Kzht5Wnn8ykcuKtwr3l3rKJqc5qg0MIDvCjZhYjkBA2MbtbzxOGcRw1 XTq5GHxxjv9+7V6Y31tfLVsAhKTKeAl+1yJcA6f3G0tRx7AMxHWqeWU8xSklwiEZ4NPE V57L4QGsrLY87SJSuVpp7qxzBsG0k9qPvxrlIOLTnBDGepxPX8sAliqfsLuT3AqDMNea +SuuTyWFBT6b1xgQKQgzNapi4bkAWvhzjbP0vhLPd35HM1OK+TXNPNdAg5eVV4RQ492T yx6UunpRElXp7MicnZh/eZ0HVrKdFNYACijwCN4+mPyfaNLArh8+pf0Phh9MkBi3On7z dMSQ== ARC-Authentication-Results: i=1; mx.google.com; spf=neutral (google.com: 148.163.156.1 is neither permitted nor denied by best guess record for domain of ravi.bangoria@linux.vnet.ibm.com) smtp.mailfrom=ravi.bangoria@linux.vnet.ibm.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=ibm.com Authentication-Results: mx.google.com; spf=neutral (google.com: 148.163.156.1 is neither permitted nor denied by best guess record for domain of ravi.bangoria@linux.vnet.ibm.com) smtp.mailfrom=ravi.bangoria@linux.vnet.ibm.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=ibm.com Subject: Re: [PATCH 5/8] trace_uprobe: Support SDT markers having reference count (semaphore) To: Oleg Nesterov Cc: mhiramat@kernel.org, peterz@infradead.org, srikar@linux.vnet.ibm.com, acme@kernel.org, ananth@linux.vnet.ibm.com, akpm@linux-foundation.org, alexander.shishkin@linux.intel.com, alexis.berlemont@gmail.com, corbet@lwn.net, dan.j.williams@intel.com, gregkh@linuxfoundation.org, huawei.libin@huawei.com, hughd@google.com, jack@suse.cz, jglisse@redhat.com, jolsa@redhat.com, kan.liang@intel.com, kirill.shutemov@linux.intel.com, kjlx@templeofstupid.com, kstewart@linuxfoundation.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.com, milian.wolff@kdab.com, mingo@redhat.com, namhyung@kernel.org, naveen.n.rao@linux.vnet.ibm.com, pc@us.ibm.com, pombredanne@nexb.com, rostedt@goodmis.org, tglx@linutronix.de, tmricht@linux.vnet.ibm.com, willy@infradead.org, yao.jin@linux.intel.com, fengguang.wu@intel.com, Ravi Bangoria References: <20180313125603.19819-1-ravi.bangoria@linux.vnet.ibm.com> <20180313125603.19819-6-ravi.bangoria@linux.vnet.ibm.com> <20180315150156.GA19767@redhat.com> From: Ravi Bangoria Date: Fri, 16 Mar 2018 15:01:05 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180315150156.GA19767@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-TM-AS-GCONF: 00 x-cbid: 18031609-0020-0000-0000-00000405DDE2 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18031609-0021-0000-0000-00004299E987 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-03-16_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1803160115 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1594827101403620100?= X-GMAIL-MSGID: =?utf-8?q?1595085983807901177?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 03/15/2018 08:31 PM, Oleg Nesterov wrote: > On 03/13, Ravi Bangoria wrote: >> +sdt_update_ref_ctr(struct mm_struct *mm, unsigned long vaddr, short d) >> +{ >> + void *kaddr; >> + struct page *page; >> + struct vm_area_struct *vma; >> + int ret = 0; >> + unsigned short orig = 0; >> + >> + if (vaddr == 0) >> + return -EINVAL; >> + >> + ret = get_user_pages_remote(NULL, mm, vaddr, 1, >> + FOLL_FORCE | FOLL_WRITE, &page, &vma, NULL); >> + if (ret <= 0) >> + return ret; >> + >> + kaddr = kmap_atomic(page); >> + memcpy(&orig, kaddr + (vaddr & ~PAGE_MASK), sizeof(orig)); >> + orig += d; >> + memcpy(kaddr + (vaddr & ~PAGE_MASK), &orig, sizeof(orig)); >> + kunmap_atomic(kaddr); > Hmm. Why memcpy? You could simply do > > kaddr = kmap_atomic(); > unsigned short *ptr = kaddr + (vaddr & ~PAGE_MASK); > *ptr += d; > kunmap_atomic(); Yes, that should work. Will change it. Thanks for the review, Ravi