curl: Eliminate unnecessary use of curl_multi_socket_all

curl_multi_socket_all is a deprecated catch-all which checks for
activities on all open curl sockets. We have enough information from
the event loop to check only the sockets with activity. This change
removes use of curl_multi_socket_all in favour of
curl_multi_socket_action called with the relevant handle.

At the same time, it also ensures that the driver only checks for
completion of read operations after reading from a socket, rather than
both reading and writing.
Signed-off-by: NMatthew Booth <mbooth@redhat.com>
Tested-by: NRichard W.M. Jones <rjones@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/curl.c

@@ -71,6 +71,7 @@ typedef struct CURLState
     struct BDRVCURLState *s;
     CURLAIOCB *acb[CURL_NUM_ACB];
     CURL *curl;
+    curl_socket_t sock_fd;
     char *orig_buf;
     size_t buf_start;
     size_t buf_off;
@@ -92,6 +93,7 @@ typedef struct BDRVCURLState {
 
 static void curl_clean_state(CURLState *s);
 static void curl_multi_do(void *arg);
+static void curl_multi_read(void *arg);
 
 #ifdef NEED_CURL_TIMER_CALLBACK
 static int curl_timer_cb(CURLM *multi, long timeout_ms, void *opaque)
@@ -113,16 +115,20 @@ static int curl_timer_cb(CURLM *multi, long timeout_ms, void *opaque)
 static int curl_sock_cb(CURL *curl, curl_socket_t fd, int action,
                         void *s, void *sp)
 {
+    CURLState *state = NULL;
+    curl_easy_getinfo(curl, CURLINFO_PRIVATE, (char **)&state);
+    state->sock_fd = fd;
+
     DPRINTF("CURL (AIO): Sock action %d on fd %d\n", action, fd);
     switch (action) {
         case CURL_POLL_IN:
-            qemu_aio_set_fd_handler(fd, curl_multi_do, NULL, s);
+            qemu_aio_set_fd_handler(fd, curl_multi_read, NULL, state);
             break;
         case CURL_POLL_OUT:
-            qemu_aio_set_fd_handler(fd, NULL, curl_multi_do, s);
+            qemu_aio_set_fd_handler(fd, NULL, curl_multi_do, state);
             break;
         case CURL_POLL_INOUT:
-            qemu_aio_set_fd_handler(fd, curl_multi_do, curl_multi_do, s);
+            qemu_aio_set_fd_handler(fd, curl_multi_read, curl_multi_do, state);
             break;
         case CURL_POLL_REMOVE:
             qemu_aio_set_fd_handler(fd, NULL, NULL, NULL);
@@ -236,7 +242,7 @@ static int curl_find_buf(BDRVCURLState *s, size_t start, size_t len,
     return FIND_RET_NONE;
 }
 
-static void curl_multi_read(BDRVCURLState *s)
+static void curl_multi_check_completion(BDRVCURLState *s)
 {
     int msgs_in_queue;
 
@@ -286,19 +292,26 @@ static void curl_multi_read(BDRVCURLState *s)
 
 static void curl_multi_do(void *arg)
 {
-    BDRVCURLState *s = (BDRVCURLState *)arg;
+    CURLState *s = (CURLState *)arg;
     int running;
     int r;
 
-    if (!s->multi) {
+    if (!s->s->multi) {
         return;
     }
 
     do {
-        r = curl_multi_socket_all(s->multi, &running);
+        r = curl_multi_socket_action(s->s->multi, s->sock_fd, 0, &running);
     } while(r == CURLM_CALL_MULTI_PERFORM);
 
-    curl_multi_read(s);
+}
+
+static void curl_multi_read(void *arg)
+{
+    CURLState *s = (CURLState *)arg;
+
+    curl_multi_do(arg);
+    curl_multi_check_completion(s->s);
 }
 
 static void curl_multi_timeout_do(void *arg)
@@ -313,7 +326,7 @@ static void curl_multi_timeout_do(void *arg)
 
     curl_multi_socket_action(s->multi, CURL_SOCKET_TIMEOUT, 0, &running);
 
-    curl_multi_read(s);
+    curl_multi_check_completion(s);
 #else
     abort();
 #endif
@@ -529,7 +542,6 @@ static int curl_open(BlockDriverState *bs, QDict *options, int flags,
     // 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);