[RFC PATCH 2/9] block/curl: Remove readahead support

[David Edmondson]

Block based caching and the current readahead support do not interact
well, so remove readahead support before adding block
caching. Readahead will be re-added later.

Signed-off-by: David Edmondson <david.edmondson@oracle.com>
---
 block/curl.c                          | 23 ++++-------------------
 docs/system/device-url-syntax.rst.inc |  7 -------
 qapi/block-core.json                  |  4 ----
 3 files changed, 4 insertions(+), 30 deletions(-)

diff --git a/block/curl.c b/block/curl.c
index 32ec760f66..d0c74d7de5 100644
--- a/block/curl.c
+++ b/block/curl.c
@@ -65,7 +65,6 @@ static CURLMcode __curl_multi_socket_action(CURLM 
*multi_handle,
 #define CURL_TIMEOUT_MAX 10000
 
 #define CURL_BLOCK_OPT_URL       "url"
-#define CURL_BLOCK_OPT_READAHEAD "readahead"
 #define CURL_BLOCK_OPT_SSLVERIFY "sslverify"
 #define CURL_BLOCK_OPT_TIMEOUT "timeout"
 #define CURL_BLOCK_OPT_COOKIE    "cookie"
@@ -76,7 +75,6 @@ static CURLMcode __curl_multi_socket_action(CURLM 
*multi_handle,
 #define CURL_BLOCK_OPT_PROXY_PASSWORD_SECRET "proxy-password-secret"
 #define CURL_BLOCK_OPT_OFFSET "offset"
 
-#define CURL_BLOCK_OPT_READAHEAD_DEFAULT (256 * 1024)
 #define CURL_BLOCK_OPT_SSLVERIFY_DEFAULT true
 #define CURL_BLOCK_OPT_TIMEOUT_DEFAULT 5
 
@@ -124,7 +122,6 @@ typedef struct BDRVCURLState {
     uint64_t len;
     CURLState states[CURL_NUM_STATES];
     char *url;
-    size_t readahead_size;
     bool sslverify;
     uint64_t timeout;
     char *cookie;
@@ -615,11 +612,6 @@ static QemuOptsList runtime_opts = {
             .type = QEMU_OPT_STRING,
             .help = "URL to open",
         },
-        {
-            .name = CURL_BLOCK_OPT_READAHEAD,
-            .type = QEMU_OPT_SIZE,
-            .help = "Readahead size",
-        },
         {
             .name = CURL_BLOCK_OPT_SSLVERIFY,
             .type = QEMU_OPT_BOOL,
@@ -705,14 +697,6 @@ static int curl_open(BlockDriverState *bs, QDict *options, 
int flags,
         goto out_noclean;
     }
 
-    s->readahead_size = qemu_opt_get_size(opts, CURL_BLOCK_OPT_READAHEAD,
-                                          CURL_BLOCK_OPT_READAHEAD_DEFAULT);
-    if ((s->readahead_size & 0x1ff) != 0) {
-        error_setg(errp, "HTTP_READAHEAD_SIZE %zd is not a multiple of 512",
-                   s->readahead_size);
-        goto out_noclean;
-    }
-
     s->timeout = qemu_opt_get_number(opts, CURL_BLOCK_OPT_TIMEOUT,
                                      CURL_BLOCK_OPT_TIMEOUT_DEFAULT);
     if (s->timeout > CURL_TIMEOUT_MAX) {
@@ -898,7 +882,7 @@ static void curl_setup_preadv(BlockDriverState *bs, 
CURLAIOCB *acb)
     state->buf_off = 0;
     g_free(state->orig_buf);
     state->buf_start = start;
-    state->buf_len = MIN(acb->end + s->readahead_size, s->len - start);
+    state->buf_len = MIN(acb->end, s->len - start);
     end = start + state->buf_len - 1;
     state->orig_buf = g_try_malloc(state->buf_len);
     if (state->buf_len && state->orig_buf == NULL) {
@@ -971,8 +955,9 @@ static void curl_refresh_filename(BlockDriverState *bs)
 {
     BDRVCURLState *s = bs->opaque;
 
-    /* "readahead" and "timeout" do not change the guest-visible data,
-     * so ignore them */
+    /*
+     * "timeout" does not change the guest-visible data, so ignore it.
+     */
     if (s->sslverify != CURL_BLOCK_OPT_SSLVERIFY_DEFAULT ||
         s->cookie || s->username || s->password || s->proxyusername ||
         s->proxypassword)
diff --git a/docs/system/device-url-syntax.rst.inc 
b/docs/system/device-url-syntax.rst.inc
index 33f1ddfe6d..bc38b9df38 100644
--- a/docs/system/device-url-syntax.rst.inc
+++ b/docs/system/device-url-syntax.rst.inc
@@ -174,13 +174,6 @@ These are specified using a special URL syntax.
    ``url``
       The full URL when passing options to the driver explicitly.
 
-   ``readahead``
-      The amount of data to read ahead with each range request to the
-      remote server. This value may optionally have the suffix 'T', 'G',
-      'M', 'K', 'k' or 'b'. If it does not have a suffix, it will be
-      assumed to be in bytes. The value must be a multiple of 512 bytes.
-      It defaults to 256k.
-
    ``sslverify``
       Whether to verify the remote server's certificate when connecting
       over SSL. It can have the value 'on' or 'off'. It defaults to
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 197bdc1c36..d6f5e91cc3 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -3752,9 +3752,6 @@
 #
 # @url: URL of the image file
 #
-# @readahead: Size of the read-ahead cache; must be a multiple of
-#             512 (defaults to 256 kB)
-#
 # @timeout: Timeout for connections, in seconds (defaults to 5)
 #
 # @username: Username for authentication (defaults to none)
@@ -3771,7 +3768,6 @@
 ##
 { 'struct': 'BlockdevOptionsCurlBase',
   'data': { 'url': 'str',
-            '*readahead': 'int',
             '*timeout': 'int',
             '*username': 'str',
             '*password-secret': 'str',
-- 
2.27.0