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* [Qemu-devel] [PATCH] block/curl: Implement the libcurl timer callback interface
@ 2014-01-15 17:23 Peter Maydell
  2014-01-15 21:37 ` Richard W.M. Jones
  2014-01-15 22:06 ` Paolo Bonzini
  0 siblings, 2 replies; 14+ messages in thread
From: Peter Maydell @ 2014-01-15 17:23 UTC (permalink / raw)
  To: qemu-devel; +Cc: Kevin Wolf, qemu-stable, Stefan Hajnoczi, patches

libcurl versions 7.16.0 and later have a timer callback interface which
must be implemented in order for libcurl to make forward progress (it
will sometimes rely on being called back on the timeout if there are
no file descriptors registered). Implement the callback, and use a
QEMU AIO timer to ensure we prod libcurl again when it asks us to.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
This fixes the problem I was seeing where trying to use the curl block
backend just hung. I'm not sure whether all libcurl versions that provide
the timer callback API require its use, but it shouldn't hurt.

This is probably a candidate for stable if it passes code review.

 block/curl.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/block/curl.c b/block/curl.c
index a603936..3c4c5fc 100644
--- a/block/curl.c
+++ b/block/curl.c
@@ -34,6 +34,11 @@
 #define DPRINTF(fmt, ...) do { } while (0)
 #endif
 
+#if LIBCURL_VERSION_NUM >= 0x071000
+/* The multi interface timer callback was introduced in 7.16.0 */
+#define NEED_CURL_TIMER_CALLBACK
+#endif
+
 #define PROTOCOLS (CURLPROTO_HTTP | CURLPROTO_HTTPS | \
                    CURLPROTO_FTP | CURLPROTO_FTPS | \
                    CURLPROTO_TFTP)
@@ -77,6 +82,7 @@ typedef struct CURLState
 
 typedef struct BDRVCURLState {
     CURLM *multi;
+    QEMUTimer timer;
     size_t len;
     CURLState states[CURL_NUM_STATES];
     char *url;
@@ -87,6 +93,23 @@ typedef struct BDRVCURLState {
 static void curl_clean_state(CURLState *s);
 static void curl_multi_do(void *arg);
 
+#ifdef NEED_CURL_TIMER_CALLBACK
+static int curl_timer_cb(CURLM *multi, long timeout_ms, void *opaque)
+{
+    BDRVCURLState *s = opaque;
+
+    DPRINTF("CURL: timer callback timeout_ms %ld\n", timeout_ms);
+    if (timeout_ms == -1) {
+        timer_del(&s->timer);
+    } else {
+        int64_t timeout_ns = (int64_t)timeout_ms * 1000 * 1000;
+        timer_mod(&s->timer,
+                  qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + timeout_ns);
+    }
+    return 0;
+}
+#endif
+
 static int curl_sock_cb(CURL *curl, curl_socket_t fd, int action,
                         void *s, void *sp)
 {
@@ -473,12 +496,20 @@ static int curl_open(BlockDriverState *bs, QDict *options, int flags,
     curl_easy_cleanup(state->curl);
     state->curl = NULL;
 
+    aio_timer_init(bdrv_get_aio_context(bs), &s->timer,
+                   QEMU_CLOCK_REALTIME, SCALE_NS,
+                   curl_multi_do, s);
+
     // Now we know the file exists and its size, so let's
     // initialize the multi interface!
 
     s->multi = curl_multi_init();
     curl_multi_setopt(s->multi, CURLMOPT_SOCKETDATA, s);
     curl_multi_setopt(s->multi, CURLMOPT_SOCKETFUNCTION, curl_sock_cb);
+#ifdef NEED_CURL_TIMER_CALLBACK
+    curl_multi_setopt(s->multi, CURLMOPT_TIMERDATA, s);
+    curl_multi_setopt(s->multi, CURLMOPT_TIMERFUNCTION, curl_timer_cb);
+#endif
     curl_multi_do(s);
 
     qemu_opts_del(opts);
@@ -597,6 +628,9 @@ static void curl_close(BlockDriverState *bs)
     }
     if (s->multi)
         curl_multi_cleanup(s->multi);
+
+    timer_del(&s->timer);
+
     g_free(s->url);
 }
 
-- 
1.7.11.4

^ permalink raw reply related	[flat|nested] 14+ messages in thread
* [Qemu-devel] [PATCH] block/curl: Implement the libcurl timer callback interface
@ 2014-01-24 13:56 Paolo Bonzini
  2014-01-24 15:01 ` Kevin Wolf
  0 siblings, 1 reply; 14+ messages in thread
From: Paolo Bonzini @ 2014-01-24 13:56 UTC (permalink / raw)
  To: qemu-devel; +Cc: kwolf, Peter Maydell, stefanha

From: Peter Maydell <peter.maydell@linaro.org>

libcurl versions 7.16.0 and later have a timer callback interface which
must be implemented in order for libcurl to make forward progress (it
will sometimes rely on being called back on the timeout if there are
no file descriptors registered). Implement the callback, and use a
QEMU AIO timer to ensure we prod libcurl again when it asks us to.

Based on Peter's original patch plus my fix to add curl_multi_timeout_do.
Should compile just fine even on older versions of libcurl.

I also tried copy-on-read and streaming:

    $ ./qemu-img create -f qcow2 -o \
         backing_file=http://download.fedoraproject.org/pub/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso \
         foo.qcow2 1G
    $ x86_64-softmmu/qemu-system-x86_64 \
         -drive if=none,file=foo.qcow2,copy-on-read=on,id=cd \
         -device ide-cd,drive=cd --enable-kvm -m 1024

Direct http usage is probably too slow, but with copy-on-read ultimately
the image does boot!

After some time, streaming gets canceled by an EIO, which needs further
investigation.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/curl.c | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 70 insertions(+), 11 deletions(-)

diff --git a/block/curl.c b/block/curl.c
index a603936..a807584 100644
--- a/block/curl.c
+++ b/block/curl.c
@@ -34,6 +34,11 @@
 #define DPRINTF(fmt, ...) do { } while (0)
 #endif
 
+#if LIBCURL_VERSION_NUM >= 0x071000
+/* The multi interface timer callback was introduced in 7.16.0 */
+#define NEED_CURL_TIMER_CALLBACK
+#endif
+
 #define PROTOCOLS (CURLPROTO_HTTP | CURLPROTO_HTTPS | \
                    CURLPROTO_FTP | CURLPROTO_FTPS | \
                    CURLPROTO_TFTP)
@@ -77,6 +82,7 @@ typedef struct CURLState
 
 typedef struct BDRVCURLState {
     CURLM *multi;
+    QEMUTimer timer;
     size_t len;
     CURLState states[CURL_NUM_STATES];
     char *url;
@@ -87,6 +93,23 @@ typedef struct BDRVCURLState {
 static void curl_clean_state(CURLState *s);
 static void curl_multi_do(void *arg);
 
+#ifdef NEED_CURL_TIMER_CALLBACK
+static int curl_timer_cb(CURLM *multi, long timeout_ms, void *opaque)
+{
+    BDRVCURLState *s = opaque;
+
+    DPRINTF("CURL: timer callback timeout_ms %ld\n", timeout_ms);
+    if (timeout_ms == -1) {
+        timer_del(&s->timer);
+    } else {
+        int64_t timeout_ns = (int64_t)timeout_ms * 1000 * 1000;
+        timer_mod(&s->timer,
+                  qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + timeout_ns);
+    }
+    return 0;
+}
+#endif
+
 static int curl_sock_cb(CURL *curl, curl_socket_t fd, int action,
                         void *s, void *sp)
 {
@@ -209,20 +232,10 @@ static int curl_find_buf(BDRVCURLState *s, size_t start, size_t len,
     return FIND_RET_NONE;
 }
 
-static void curl_multi_do(void *arg)
+static void curl_multi_read(BDRVCURLState *s)
 {
-    BDRVCURLState *s = (BDRVCURLState *)arg;
-    int running;
-    int r;
     int msgs_in_queue;
 
-    if (!s->multi)
-        return;
-
-    do {
-        r = curl_multi_socket_all(s->multi, &running);
-    } while(r == CURLM_CALL_MULTI_PERFORM);
-
     /* Try to find done transfers, so we can free the easy
      * handle again. */
     do {
@@ -266,6 +279,41 @@ static void curl_multi_do(void *arg)
     } while(msgs_in_queue);
 }
 
+static void curl_multi_do(void *arg)
+{
+    BDRVCURLState *s = (BDRVCURLState *)arg;
+    int running;
+    int r;
+
+    if (!s->multi) {
+        return;
+    }
+
+    do {
+        r = curl_multi_socket_all(s->multi, &running);
+    } while(r == CURLM_CALL_MULTI_PERFORM);
+
+    curl_multi_read(s);
+}
+
+static void curl_multi_timeout_do(void *arg)
+{
+#ifdef NEED_CURL_TIMER_CALLBACK
+    BDRVCURLState *s = (BDRVCURLState *)arg;
+    int running;
+
+    if (!s->multi) {
+        return;
+    }
+
+    curl_multi_socket_action(s->multi, CURL_SOCKET_TIMEOUT, 0, &running);
+
+    curl_multi_read(s);
+#else
+    abort();
+#endif
+}
+
 static CURLState *curl_init_state(BDRVCURLState *s)
 {
     CURLState *state = NULL;
@@ -473,12 +521,20 @@ static int curl_open(BlockDriverState *bs, QDict *options, int flags,
     curl_easy_cleanup(state->curl);
     state->curl = NULL;
 
+    aio_timer_init(bdrv_get_aio_context(bs), &s->timer,
+                   QEMU_CLOCK_REALTIME, SCALE_NS,
+                   curl_multi_timeout_do, s);
+
     // Now we know the file exists and its size, so let's
     // initialize the multi interface!
 
     s->multi = curl_multi_init();
     curl_multi_setopt(s->multi, CURLMOPT_SOCKETDATA, s);
     curl_multi_setopt(s->multi, CURLMOPT_SOCKETFUNCTION, curl_sock_cb);
+#ifdef NEED_CURL_TIMER_CALLBACK
+    curl_multi_setopt(s->multi, CURLMOPT_TIMERDATA, s);
+    curl_multi_setopt(s->multi, CURLMOPT_TIMERFUNCTION, curl_timer_cb);
+#endif
     curl_multi_do(s);
 
     qemu_opts_del(opts);
@@ -597,6 +653,9 @@ static void curl_close(BlockDriverState *bs)
     }
     if (s->multi)
         curl_multi_cleanup(s->multi);
+
+    timer_del(&s->timer);
+
     g_free(s->url);
 }
 
-- 
1.8.4.2

^ permalink raw reply related	[flat|nested] 14+ messages in thread
end of thread, other threads:[~2014-01-24 15:01 UTC | newest]

Thread overview: 14+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2014-01-15 17:23 [Qemu-devel] [PATCH] block/curl: Implement the libcurl timer callback interface Peter Maydell
2014-01-15 21:37 ` Richard W.M. Jones
2014-01-15 21:56   ` Peter Maydell
2014-01-16  8:40     ` Paolo Bonzini
2014-01-15 22:06 ` Paolo Bonzini
2014-01-15 22:15   ` Peter Maydell
2014-01-16  8:38     ` Paolo Bonzini
2014-01-16  9:55       ` Peter Maydell
2014-01-16 10:15         ` Paolo Bonzini
2014-01-16  9:12   ` Richard W.M. Jones
2014-01-16  9:24     ` Richard W.M. Jones
2014-01-16  9:52       ` Kevin Wolf
  -- strict thread matches above, loose matches on Subject: below --
2014-01-24 13:56 Paolo Bonzini
2014-01-24 15:01 ` Kevin Wolf

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