Blame SOURCES/0118-p2v-Poll-to-make-Cancel-Conversion-button-more-respo.patch

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From a5806c1b4be3f74b25ec733328259e7966af6af6 Mon Sep 17 00:00:00 2001
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From: "Richard W.M. Jones" <rjones@redhat.com>
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Date: Mon, 20 Jun 2016 10:18:22 +0100
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Subject: [PATCH] p2v: Poll to make Cancel Conversion button more responsive.
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Previously cancelling the conversion only set a flag, which was
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checked when the run dialog displayed new output from virt-v2v.  When
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virt-v2v was showing hundreds of debugging messages, this wasn't a
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problem, but now that we are hiding those messages, cancelling the
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conversion might mean a wait of seconds or minutes.
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By polling (albeit infrequently) we can make the cancel button more
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responsive.
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(cherry picked from commit 6da4941db7f8a85997d6281b9b4c5165768e6489)
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---
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 p2v/conversion.c | 27 +++++++++++++++++++++++++--
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 1 file changed, 25 insertions(+), 2 deletions(-)
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diff --git a/p2v/conversion.c b/p2v/conversion.c
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index b54f971..de2a4b2 100644
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--- a/p2v/conversion.c
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+++ b/p2v/conversion.c
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@@ -25,6 +25,7 @@
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 #include <fcntl.h>
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 #include <inttypes.h>
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 #include <unistd.h>
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+#include <poll.h>
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 #include <time.h>
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 #include <errno.h>
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 #include <error.h>
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@@ -346,13 +347,35 @@ start_conversion (struct config *config,
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   }
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   /* Read output from the virt-v2v process and echo it through the
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-   * notify function, until virt-v2v closes the connection.
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+   * notify function, until virt-v2v closes the connection.  We
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+   * actually poll in this loop (albeit it only every 2 seconds) so
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+   * that the user won't have to wait too long between pressing the
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+   * cancel button and having the conversion cancelled.
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    */
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   while (!is_cancel_requested ()) {
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+    int fd = mexp_get_fd (control_h);
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+    struct pollfd fds[1];
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+    int rp;
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     char buf[257];
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     ssize_t r;
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-    r = read (mexp_get_fd (control_h), buf, sizeof buf - 1);
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+    fds[0].fd = fd;
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+    fds[0].events = POLLIN;
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+    fds[0].revents = 0;
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+    rp = poll (fds, 1, 2000 /* ms */);
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+    if (rp == -1) {
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+      /* See comment about this in miniexpect.c. */
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+      if (errno == EIO)
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+        break;
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+      set_conversion_error ("poll: %m");
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+      goto out;
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+    }
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+    else if (rp == 0)
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+      /* Timeout. */
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+      continue;
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+    /* ... else rp == 1, ignore revents and just do the read. */
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+
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+    r = read (fd, buf, sizeof buf - 1);
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     if (r == -1) {
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       /* See comment about this in miniexpect.c. */
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       if (errno == EIO)
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-- 
aa0300
2.7.4
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