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Tue, 22 Sep 2020 10:18:24 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.192.146]) by smtp.corp.redhat.com (Postfix) with SMTP id 5F05B9CBA; Tue, 22 Sep 2020 10:18:17 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 22 Sep 2020 12:18:24 +0200 (CEST) Date: Tue, 22 Sep 2020 12:18:16 +0200 From: Oleg Nesterov To: Peter Xu Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jason Gunthorpe , Andrew Morton , Jan Kara , Michal Hocko , Kirill Tkhai , Kirill Shutemov , Hugh Dickins , Christoph Hellwig , Andrea Arcangeli , John Hubbard , Leon Romanovsky , Linus Torvalds , Jann Horn Subject: Re: [PATCH 3/5] mm: Rework return value for copy_one_pte() Message-ID: <20200922101815.GB11679@redhat.com> References: <20200921211744.24758-1-peterx@redhat.com> <20200921211744.24758-4-peterx@redhat.com> <20200922100840.GA11679@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200922100840.GA11679@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 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 09/22, Oleg Nesterov wrote: > > On 09/21, Peter Xu wrote: > > > > @@ -866,13 +877,18 @@ static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm, > > pte_unmap_unlock(orig_dst_pte, dst_ptl); > > cond_resched(); > > > > - if (entry.val) { > > - if (add_swap_count_continuation(entry, GFP_KERNEL) < 0) > > + switch (copy_ret) { > > + case COPY_MM_SWAP_CONT: > > + if (add_swap_count_continuation(data.entry, GFP_KERNEL) < 0) > > return -ENOMEM; > > - progress = 0; > > + break; > > Note that you didn't clear copy_ret, it is still COPY_MM_SWAP_CONT, > > > + default: > > + break; > > } > > + > > if (addr != end) > > goto again; > > After that the main loop can stop again because of need_resched(), and > in this case add_swap_count_continuation(data.entry) will be called again? No, this is not possible, copy_one_pte() should be called at least once, progress = 0 before restart. Sorry for noise. Oleg.