[v5,06/11] curl: introduce CURLDataCache

diff --git a/block/curl.c b/block/curl.c
index 4fd5bb9..e387ae1 100644
--- a/block/curl.c
+++ b/block/curl.c
@@ -43,10 +43,6 @@ 
 #define SECTOR_SIZE     512
 #define READ_AHEAD_SIZE (256 * 1024)
 
-#define FIND_RET_NONE   0
-#define FIND_RET_OK     1
-#define FIND_RET_WAIT   2
-
 struct BDRVCURLState;
 
 typedef struct CURLAIOCB {
@@ -61,6 +57,16 @@  typedef struct CURLAIOCB {
     size_t end;
 } CURLAIOCB;
 
+typedef struct CURLDataCache {
+    char *data;
+    size_t base_pos;
+    size_t data_len;
+    size_t write_pos;
+    /* Ref count for CURLState */
+    int use_count;
+    QLIST_ENTRY(CURLDataCache) next;
+} CURLDataCache;
+
 typedef struct CURLState
 {
     struct BDRVCURLState *s;
@@ -90,6 +96,8 @@  typedef struct BDRVCURLState {
     char *url;
     size_t readahead_size;
     QEMUTimer *timer;
+    /* List of data cache ordered by access, freed from tail */
+    QLIST_HEAD(, CURLDataCache) cache;
     /* Whether http server accept range in header */
     bool accept_range;
 } BDRVCURLState;
@@ -98,6 +106,19 @@  static void curl_clean_state(CURLState *s);
 static void curl_fd_handler(void *arg);
 static int curl_aio_flush(void *opaque);
 
+static CURLDataCache *curl_find_cache(BDRVCURLState *bs,
+                                      size_t start, size_t len)
+{
+    CURLDataCache *c;
+    QLIST_FOREACH(c, &bs->cache, next) {
+        if (start >= c->base_pos &&
+            start + len <= c->base_pos + c->write_pos) {
+            return c;
+        }
+    }
+    return NULL;
+}
+
 static int curl_sock_cb(CURL *curl, curl_socket_t fd, int action,
                         void *s, void *sp)
 {
@@ -181,6 +202,23 @@  static int curl_multi_timer_cb(CURLM *multi, long timeout_ms, void *s)
     return 0;
 }
 
+static void curl_complete_io(BDRVCURLState *bs, CURLAIOCB *acb,
+                             CURLDataCache *cache)
+{
+    size_t aio_base = acb->sector_num * SECTOR_SIZE;
+    size_t aio_bytes = acb->nb_sectors * SECTOR_SIZE;
+    size_t off = aio_base - cache->base_pos;
+
+    qemu_iovec_from_buf(acb->qiov, 0, cache->data + off, aio_bytes);
+    acb->common.cb(acb->common.opaque, 0);
+    DPRINTF("AIO Request OK: %10zd %10zd\n", aio_base, aio_bytes);
+    qemu_aio_release(acb);
+    acb = NULL;
+    /* Move cache next in the list */
+    QLIST_REMOVE(cache, next);
+    QLIST_INSERT_HEAD(&bs->cache, cache, next);
+}
+
 static size_t curl_read_cb(void *ptr, size_t size, size_t nmemb, void *opaque)
 {
     CURLState *s = ((CURLState*)opaque);
@@ -214,59 +252,6 @@  read_end:
     return realsize;
 }
 
-static int curl_find_buf(BDRVCURLState *s, size_t start, size_t len,
-                         CURLAIOCB *acb)
-{
-    int i;
-    size_t end = start + len;
-
-    for (i=0; i<CURL_NUM_STATES; i++) {
-        CURLState *state = &s->states[i];
-        size_t buf_end = (state->buf_start + state->buf_off);
-        size_t buf_fend = (state->buf_start + state->buf_len);
-
-        if (!state->orig_buf)
-            continue;
-        if (!state->buf_off)
-            continue;
-
-        // Does the existing buffer cover our section?
-        if ((start >= state->buf_start) &&
-            (start <= buf_end) &&
-            (end >= state->buf_start) &&
-            (end <= buf_end))
-        {
-            char *buf = state->orig_buf + (start - state->buf_start);
-
-            qemu_iovec_from_buf(acb->qiov, 0, buf, len);
-            acb->common.cb(acb->common.opaque, 0);
-
-            return FIND_RET_OK;
-        }
-
-        // Wait for unfinished chunks
-        if ((start >= state->buf_start) &&
-            (start <= buf_fend) &&
-            (end >= state->buf_start) &&
-            (end <= buf_fend))
-        {
-            int j;
-
-            acb->start = start - state->buf_start;
-            acb->end = acb->start + len;
-
-            for (j=0; j<CURL_NUM_ACB; j++) {
-                if (!state->acb[j]) {
-                    state->acb[j] = acb;
-                    return FIND_RET_WAIT;
-                }
-            }
-        }
-    }
-
-    return FIND_RET_NONE;
-}
-
 static void curl_fd_handler(void *arg)
 {
     CURLSockInfo *sock = (CURLSockInfo *)arg;
@@ -299,7 +284,9 @@  static void curl_fd_handler(void *arg)
             case CURLMSG_DONE:
             {
                 CURLState *state = NULL;
-                curl_easy_getinfo(msg->easy_handle, CURLINFO_PRIVATE, (char**)&state);
+                curl_easy_getinfo(msg->easy_handle,
+                                  CURLINFO_PRIVATE,
+                                  (char **)&state);
 
                 /* ACBs for successful messages get completed in curl_read_cb */
                 if (msg->data.result != CURLE_OK) {
@@ -495,6 +482,7 @@  static int curl_open(BlockDriverState *bs, QDict *options, int flags)
     }
 
     QLIST_INIT(&s->socks);
+    QLIST_INIT(&s->cache);
 
     DPRINTF("CURL: Opening %s\n", file);
     s->url = g_strdup(file);
@@ -589,26 +577,24 @@  static const AIOCBInfo curl_aiocb_info = {
 static void curl_readv_bh_cb(void *p)
 {
     CURLState *state;
-
+    CURLDataCache *cache = NULL;
     CURLAIOCB *acb = p;
     BDRVCURLState *s = acb->common.bs->opaque;
+    size_t aio_base, aio_bytes;
 
     qemu_bh_delete(acb->bh);
     acb->bh = NULL;
 
+    aio_base = acb->sector_num * SECTOR_SIZE;
+    aio_bytes = acb->nb_sectors * SECTOR_SIZE;
+
     size_t start = acb->sector_num * SECTOR_SIZE;
     size_t end;
 
-    // In case we have the requested data already (e.g. read-ahead),
-    // we can just call the callback and be done.
-    switch (curl_find_buf(s, start, acb->nb_sectors * SECTOR_SIZE, acb)) {
-        case FIND_RET_OK:
-            qemu_aio_release(acb);
-            // fall through
-        case FIND_RET_WAIT:
-            return;
-        default:
-            break;
+    cache = curl_find_cache(s, aio_base, aio_bytes);
+    if (cache) {
+        curl_complete_io(s, acb, cache);
+        return;
     }
 
     // No cache found, so let's start a new request
@@ -691,6 +677,18 @@  static void curl_close(BlockDriverState *bs)
     if (s->multi)
         curl_multi_cleanup(s->multi);
 
+    while (!QLIST_EMPTY(&s->cache)) {
+        CURLDataCache *cache = QLIST_FIRST(&s->cache);
+        assert(cache->use_count == 0);
+        if (cache->data) {
+            g_free(cache->data);
+            cache->data = NULL;
+        }
+        QLIST_REMOVE(cache, next);
+        g_free(cache);
+        cache = NULL;
+    }
+
     while (!QLIST_EMPTY(&s->socks)) {
         CURLSockInfo *sock = QLIST_FIRST(&s->socks);
         QLIST_REMOVE(sock, next);