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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id c5sm9841274wma.3.2020.03.09.05.30.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Mar 2020 05:30:45 -0700 (PDT) Date: Mon, 9 Mar 2020 13:30:45 +0100 From: Oleksandr Natalenko To: Vlastimil Babka Cc: Minchan Kim , Andrew Morton , LKML , linux-mm , linux-api@vger.kernel.org, Suren Baghdasaryan , Tim Murray , Daniel Colascione , Sandeep Patil , Sonny Rao , Brian Geffon , Michal Hocko , Johannes Weiner , Shakeel Butt , John Dias , Joel Fernandes , Jann Horn , alexander.h.duyck@linux.intel.com, sj38.park@gmail.com Subject: Re: [PATCH v7 6/7] mm/madvise: employ mmget_still_valid for write lock Message-ID: <20200309123045.o4cwni3ra6zq6ha2@butterfly.localdomain> References: <20200302193630.68771-1-minchan@kernel.org> <20200302193630.68771-7-minchan@kernel.org> <20200306130303.kztv64f52qknxb6k@butterfly.localdomain> <86fc8d7b-ad6b-1691-b022-025d01e9e8e3@suse.cz> MIME-Version: 1.0 In-Reply-To: <86fc8d7b-ad6b-1691-b022-025d01e9e8e3@suse.cz> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline 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 Fri, Mar 06, 2020 at 05:03:50PM +0100, Vlastimil Babka wrote: > On 3/6/20 2:03 PM, Oleksandr Natalenko wrote: > > Hello. > >=20 > > On Fri, Mar 06, 2020 at 01:52:07PM +0100, Vlastimil Babka wrote: > >> > diff --git a/mm/madvise.c b/mm/madvise.c > >> > index e794367f681e..e77c6c1fad34 100644 > >> > --- a/mm/madvise.c > >> > +++ b/mm/madvise.c > >> > @@ -1118,6 +1118,8 @@ int do_madvise(struct task_struct *target_task= , struct mm_struct *mm, > >> > =09if (write) { > >> > =09=09if (down_write_killable(&mm->mmap_sem)) > >> > =09=09=09return -EINTR; > >> > +=09=09if (current->mm !=3D mm && !mmget_still_valid(mm)) > >> > +=09=09=09goto skip_mm; > >>=20 > >> This will return 0, is that correct? Shoudln't there be a similar erro= r e.g. as > >> when finding the task by pid fails (-ESRCH ?), because IIUC the task h= ere is > >> going away and dumping the core? > >=20 > > Yeah. > >=20 > > Something like this then: > >=20 > > =3D=3D=3D > > diff --git a/mm/madvise.c b/mm/madvise.c > > index 48d1da08c160..7ed2f4d13924 100644 > > --- a/mm/madvise.c > > +++ b/mm/madvise.c > > @@ -1122,6 +1122,10 @@ int do_madvise(struct task_struct *target_task, = struct mm_struct *mm, > > =09if (write) { > > =09=09if (down_write_killable(&mm->mmap_sem)) > > =09=09=09return -EINTR; > > +=09=09if (current->mm !=3D mm && !mmget_still_valid(mm)) { > > +=09=09=09error =3D -ESRCH; > > +=09=09=09goto skip_mm; > > +=09=09} > > =09} else { > > =09=09down_read(&mm->mmap_sem); > > =09} > > @@ -1173,6 +1177,7 @@ int do_madvise(struct task_struct *target_task, s= truct mm_struct *mm, > > =09} > > out: > > =09blk_finish_plug(&plug); > > +skip_mm: > > =09if (write) > > =09=09up_write(&mm->mmap_sem); > > =09else > >=20 > > =3D=3D=3D > >=20 > > ? >=20 > Yep, thanks. >=20 Minchan, shall you take this change into the next submission, or you'd prefer me sending it to you as a new patch? --=20 Best regards, Oleksandr Natalenko (post-factum) Principal Software Maintenance Engineer