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Shutemov" Subject: Re: [PATCH v2 1/5] mm: factor out madvise's core functionality Message-ID: <20200117181413.GC140922@google.com> References: <20200116235953.163318-1-minchan@kernel.org> <20200116235953.163318-2-minchan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 17, 2020 at 01:02:34PM +0300, Kirill Tkhai wrote: > On 17.01.2020 02:59, Minchan Kim wrote: > > This patch factor out madvise's core functionality so that upcoming > > patch can reuse it without duplication. It shouldn't change any behavior. > > > > Signed-off-by: Minchan Kim > > --- > > mm/madvise.c | 194 +++++++++++++++++++++++++++++---------------------- > > 1 file changed, 111 insertions(+), 83 deletions(-) > > > > diff --git a/mm/madvise.c b/mm/madvise.c > > index bcdb6a042787..0c901de531e4 100644 > > --- a/mm/madvise.c > > +++ b/mm/madvise.c > > @@ -35,6 +35,7 @@ > > struct madvise_walk_private { > > struct mmu_gather *tlb; > > bool pageout; > > + struct task_struct *task; > > }; > > > > /* > > @@ -306,12 +307,13 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, > > bool pageout = private->pageout; > > struct mm_struct *mm = tlb->mm; > > struct vm_area_struct *vma = walk->vma; > > + struct task_struct *task = private->task; > > pte_t *orig_pte, *pte, ptent; > > spinlock_t *ptl; > > struct page *page = NULL; > > LIST_HEAD(page_list); > > > > - if (fatal_signal_pending(current)) > > + if (fatal_signal_pending(task)) > > return -EINTR; > > This EINTR may confuse userspace. Users will think the syscall was interrupted, > and it may be restarted, but this is not true. madvise_[pageout|cold] doesn't propagate the error to userspace. > > What we care here? Current task received fatal signal, while walk_page_range(..&cold_walk_ops..) > is a long cycle. So, this check allows to break the cycle faster. > > Iteration over remote task's mm may also be long, and we still may need to break > it if current received a signal. > > So, we'd better left fatal_signal_pending(current) here. > > Maybe we need both tasks fatal_signal_pending() checks and different retvals here, > but it's up to you. Yub, let's check both processes here to bail out. Thanks for the review!