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Tue, 10 Mar 2020 15:28:16 -0700 (PDT) Date: Tue, 10 Mar 2020 15:28:15 -0700 From: Minchan Kim To: Oleksandr Natalenko Cc: Vlastimil Babka , 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: <20200310222815.GD72963@google.com> References: <20200302193630.68771-1-minchan@kernel.org> <20200302193630.68771-7-minchan@kernel.org> <20200306130303.kztv64f52qknxb6k@butterfly.localdomain> <86fc8d7b-ad6b-1691-b022-025d01e9e8e3@suse.cz> <20200309123045.o4cwni3ra6zq6ha2@butterfly.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200309123045.o4cwni3ra6zq6ha2@butterfly.localdomain> User-Agent: Mutt/1.12.2 (2019-09-21) Sender: linux-api-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Mon, Mar 09, 2020 at 01:30:45PM +0100, Oleksandr Natalenko wrote: > On Fri, Mar 06, 2020 at 05:03:50PM +0100, Vlastimil Babka wrote: > > On 3/6/20 2:03 PM, Oleksandr Natalenko wrote: > > > Hello. > > > > > > 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, > > >> > if (write) { > > >> > if (down_write_killable(&mm->mmap_sem)) > > >> > return -EINTR; > > >> > + if (current->mm != mm && !mmget_still_valid(mm)) > > >> > + goto skip_mm; > > >> > > >> This will return 0, is that correct? Shoudln't there be a similar error e.g. as > > >> when finding the task by pid fails (-ESRCH ?), because IIUC the task here is > > >> going away and dumping the core? > > > > > > Yeah. > > > > > > Something like this then: > > > > > > === > > > 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, > > > if (write) { > > > if (down_write_killable(&mm->mmap_sem)) > > > return -EINTR; > > > + if (current->mm != mm && !mmget_still_valid(mm)) { > > > + error = -ESRCH; > > > + goto skip_mm; > > > + } > > > } else { > > > down_read(&mm->mmap_sem); > > > } > > > @@ -1173,6 +1177,7 @@ int do_madvise(struct task_struct *target_task, struct mm_struct *mm, > > > } > > > out: > > > blk_finish_plug(&plug); > > > +skip_mm: > > > if (write) > > > up_write(&mm->mmap_sem); > > > else > > > > > > === > > > > > > ? > > > > Yep, thanks. > > > > Minchan, shall you take this change into the next submission, or you'd > prefer me sending it to you as a new patch? I should send patchset again so I will take it. Thanks!