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Mon, 20 Apr 2020 18:21:52 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by aserp3030.oracle.com with ESMTP id 30gb3quxyt-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 20 Apr 2020 18:21:51 +0000 Received: from abhmp0016.oracle.com (abhmp0016.oracle.com [141.146.116.22]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 03KILoEC022169; Mon, 20 Apr 2020 18:21:50 GMT Received: from ca-dmjordan1.us.oracle.com (/10.211.9.48) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 20 Apr 2020 11:21:50 -0700 Date: Mon, 20 Apr 2020 14:22:11 -0400 From: Daniel Jordan To: Michel Lespinasse Cc: Andrew Morton , linux-mm , LKML , Peter Zijlstra , Laurent Dufour , Vlastimil Babka , Matthew Wilcox , Liam Howlett , Jerome Glisse , Davidlohr Bueso , David Rientjes , Hugh Dickins , Ying Han , Jason Gunthorpe , Daniel Jordan Subject: Re: [PATCH v4 07/10] mmap locking API: add mmap_read_trylock_non_owner() Message-ID: <20200420182211.exrzkszefraeylv2@ca-dmjordan1.us.oracle.com> References: <20200415004353.130248-1-walken@google.com> <20200415004353.130248-8-walken@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200415004353.130248-8-walken@google.com> User-Agent: NeoMutt/20180716 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9597 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 spamscore=0 adultscore=0 mlxlogscore=999 phishscore=0 suspectscore=0 bulkscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004200147 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9597 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 mlxscore=0 lowpriorityscore=0 adultscore=0 suspectscore=0 bulkscore=0 clxscore=1015 malwarescore=0 phishscore=0 spamscore=0 priorityscore=1501 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004200147 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 Tue, Apr 14, 2020 at 05:43:50PM -0700, Michel Lespinasse wrote: > diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c > index 11d41f0c7005..998968659892 100644 > --- a/kernel/bpf/stackmap.c > +++ b/kernel/bpf/stackmap.c > @@ -317,7 +316,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, > * with build_id. > */ > if (!user || !current || !current->mm || irq_work_busy || > - mmap_read_trylock(current->mm) == 0) { > + !mmap_read_trylock_non_owner(current->mm)) { > /* cannot access current->mm, fall back to ips */ > for (i = 0; i < trace_nr; i++) { > id_offs[i].status = BPF_STACK_BUILD_ID_IP; > @@ -342,16 +341,10 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, > } > > if (!work) { > - mmap_read_unlock(current->mm); > + mmap_read_unlock_non_owner(current->mm); These 'non_owner' calls are not intuitive because current _is the owner, so the v3 version seems better, even if it adds a special wrapper for rwsem_release. Though it makes some sense if you think, "we're consistently using the non_owner APIs because there's a legitimate use somewhere else," so I'm fine either way. Reviewed-by: Daniel Jordan