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Violators will be prosecuted for from ; Sun, 30 Sep 2018 10:30:03 +0100 Date: Sun, 30 Sep 2018 12:29:55 +0300 From: Mike Rapoport Subject: Re: [PATCH v2 2/3] userfaultfd: selftest: generalize read and poll References: <20180930074259.18229-1-peterx@redhat.com> <20180930074259.18229-3-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180930074259.18229-3-peterx@redhat.com> Message-Id: <20180930092954.GA4062@rapoport-lnx> Sender: owner-linux-mm@kvack.org List-ID: To: Peter Xu Cc: linux-kernel@vger.kernel.org, Shuah Khan , Mike Kravetz , Jerome Glisse , linux-mm@kvack.org, Zi Yan , "Kirill A . Shutemov" , linux-kselftest@vger.kernel.org, Shaohua Li , Andrea Arcangeli , "Dr . David Alan Gilbert" , Andrew Morton On Sun, Sep 30, 2018 at 03:42:58PM +0800, Peter Xu wrote: > We do very similar things in read and poll modes, but we're copying the > codes around. Share the codes properly on reading the message and > handling the page fault to make the code cleaner. Meanwhile this solves > previous mismatch of behaviors between the two modes on that the old > code: > > - did not check EAGAIN case in read() mode > - ignored BOUNCE_VERIFY check in read() mode > > Signed-off-by: Peter Xu Acked-by: Mike Rapoport > --- > tools/testing/selftests/vm/userfaultfd.c | 77 +++++++++++++----------- > 1 file changed, 43 insertions(+), 34 deletions(-) > > diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c > index 5ff3a4f9173e..7a8c6937cc67 100644 > --- a/tools/testing/selftests/vm/userfaultfd.c > +++ b/tools/testing/selftests/vm/userfaultfd.c > @@ -451,6 +451,43 @@ static int copy_page(int ufd, unsigned long offset) > return __copy_page(ufd, offset, false); > } > > +static int uffd_read_msg(int ufd, struct uffd_msg *msg) > +{ > + int ret = read(uffd, msg, sizeof(*msg)); > + > + if (ret != sizeof(*msg)) { > + if (ret < 0) { > + if (errno == EAGAIN) > + return 1; > + else > + perror("blocking read error"), exit(1); > + } else { > + fprintf(stderr, "short read\n"), exit(1); > + } > + } > + > + return 0; > +} > + > +/* Return 1 if page fault handled by us; otherwise 0 */ > +static int uffd_handle_page_fault(struct uffd_msg *msg) > +{ > + unsigned long offset; > + > + if (msg->event != UFFD_EVENT_PAGEFAULT) > + fprintf(stderr, "unexpected msg event %u\n", > + msg->event), exit(1); > + > + if (bounces & BOUNCE_VERIFY && > + msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE) > + fprintf(stderr, "unexpected write fault\n"), exit(1); > + > + offset = (char *)(unsigned long)msg->arg.pagefault.address - area_dst; > + offset &= ~(page_size-1); > + > + return copy_page(uffd, offset); > +} > + > static void *uffd_poll_thread(void *arg) > { > unsigned long cpu = (unsigned long) arg; > @@ -458,7 +495,6 @@ static void *uffd_poll_thread(void *arg) > struct uffd_msg msg; > struct uffdio_register uffd_reg; > int ret; > - unsigned long offset; > char tmp_chr; > unsigned long userfaults = 0; > > @@ -482,25 +518,15 @@ static void *uffd_poll_thread(void *arg) > if (!(pollfd[0].revents & POLLIN)) > fprintf(stderr, "pollfd[0].revents %d\n", > pollfd[0].revents), exit(1); > - ret = read(uffd, &msg, sizeof(msg)); > - if (ret < 0) { > - if (errno == EAGAIN) > - continue; > - perror("nonblocking read error"), exit(1); > - } > + if (uffd_read_msg(uffd, &msg)) > + continue; > switch (msg.event) { > default: > fprintf(stderr, "unexpected msg event %u\n", > msg.event), exit(1); > break; > case UFFD_EVENT_PAGEFAULT: > - if (msg.arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE) > - fprintf(stderr, "unexpected write fault\n"), exit(1); > - offset = (char *)(unsigned long)msg.arg.pagefault.address - > - area_dst; > - offset &= ~(page_size-1); > - if (copy_page(uffd, offset)) > - userfaults++; > + userfaults += uffd_handle_page_fault(&msg); > break; > case UFFD_EVENT_FORK: > close(uffd); > @@ -528,8 +554,6 @@ static void *uffd_read_thread(void *arg) > { > unsigned long *this_cpu_userfaults; > struct uffd_msg msg; > - unsigned long offset; > - int ret; > > this_cpu_userfaults = (unsigned long *) arg; > *this_cpu_userfaults = 0; > @@ -538,24 +562,9 @@ static void *uffd_read_thread(void *arg) > /* from here cancellation is ok */ > > for (;;) { > - ret = read(uffd, &msg, sizeof(msg)); > - if (ret != sizeof(msg)) { > - if (ret < 0) > - perror("blocking read error"), exit(1); > - else > - fprintf(stderr, "short read\n"), exit(1); > - } > - if (msg.event != UFFD_EVENT_PAGEFAULT) > - fprintf(stderr, "unexpected msg event %u\n", > - msg.event), exit(1); > - if (bounces & BOUNCE_VERIFY && > - msg.arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE) > - fprintf(stderr, "unexpected write fault\n"), exit(1); > - offset = (char *)(unsigned long)msg.arg.pagefault.address - > - area_dst; > - offset &= ~(page_size-1); > - if (copy_page(uffd, offset)) > - (*this_cpu_userfaults)++; > + if (uffd_read_msg(uffd, &msg)) > + continue; > + (*this_cpu_userfaults) += uffd_handle_page_fault(&msg); > } > return (void *)NULL; > } > -- > 2.17.1 > -- Sincerely yours, Mike.