From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELuTIbf1/3kL6fww+XRceWLsA0TldieFpnWKKDgXehfF87HxsEVG3zY6MiCk3KnOc4l1bfnW ARC-Seal: i=1; a=rsa-sha256; t=1521126123; cv=none; d=google.com; s=arc-20160816; b=B+C82gR8YN8yk3ethPGLaZYEBEcIxiVeBXKcEXVLDjkLAo054dVea+yXWXVgFlZogO lsuKERkjZu0KRTgUo4OTOrbMkFJ2Bo9qynlCBLB+bIu1x4EiQuO+o9M4s0preED+VtrE jU5ulRNWQ2wf66+gegavBka21sIp1J67WOuPOV8z3etsX1RxRemfidDKYyh6Afle0mGg L8A64fA/jLAOdQ9MUBkk99iowI52fZ2k9pPSMYnueVIqFtOL208LQhPLYuTxSq/D4AZn wz26gptRX2ECA0pNrw/JC6ZuRvz3CvMZaLk68mNiM2I7x/egXZI+neWSwVtkr6IJbBVa gCmA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:arc-authentication-results; bh=juktfdYig9egC4zWyHjQHa9RfLgyEow4spAkeKP5gM0=; b=lip9ql2HbKmaMcbCADVN2vBf3WpqhkGBtsL5g3qK1oxCk31STilUWpJT/KRcU8ot5I Kor9Sc6hcR6wihs+dBGgt5CZoXZU5eUtvUUqP8ccFVMD8sRiLa5IpB1nW1OQwsdfi169 Ks3i07CPJob4gMt6eUOK+e1Jl28/IYPsIk2tPds+NrcmBpMrHmY9Kv4oc6c78nU8LPbZ y/afGfEBsp6RzKatG2ZZiHfgF4krxnnAcTXYwwo64IFd7KpVD9xJDMugIFKeip1WmG0Y MrvUkVYvo65TpQecwG0xBZZSn3/dhRR2Jf8P/l/aEyy0TfqmEo/6Km4vTi13HTCrCvkU 17DQ== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of oleg@redhat.com designates 66.187.233.73 as permitted sender) smtp.mailfrom=oleg@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Authentication-Results: mx.google.com; spf=pass (google.com: domain of oleg@redhat.com designates 66.187.233.73 as permitted sender) smtp.mailfrom=oleg@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Date: Thu, 15 Mar 2018 16:01:57 +0100 From: Oleg Nesterov To: Ravi Bangoria 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 Subject: Re: [PATCH 5/8] trace_uprobe: Support SDT markers having reference count (semaphore) Message-ID: <20180315150156.GA19767@redhat.com> References: <20180313125603.19819-1-ravi.bangoria@linux.vnet.ibm.com> <20180313125603.19819-6-ravi.bangoria@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180313125603.19819-6-ravi.bangoria@linux.vnet.ibm.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1594827101403620100?= X-GMAIL-MSGID: =?utf-8?q?1595016346576100567?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 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(); Oleg.