[Qemu-devel] [RFC V5 03/11] quorum: Add quorum_open() and quorum_close().

["Benoît Canet" <benoit.canet@gmail.com>]

Valid quorum resources look like
quorum:threshold/total:path/to/image_1, ... ,path/to/image_total

',' is used as a separator to allow to use networked path
'\' is the escaping character for filename containing ','
'\' escape itself

On the command line for quorum files "img,test.raw", "img2.raw"
and "img3.raw" invocation look like:

-drive file=quorum:2/3:img\\,,test.raw,,img2.raw,,img3.raw
(note the double ,, and \\)

Signed-off-by: Benoit Canet <benoit@irqsave.net>
---
 block/quorum.c |  123 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)

diff --git a/block/quorum.c b/block/quorum.c
index 19a9a44..b9fb2b9 100644
--- a/block/quorum.c
+++ b/block/quorum.c
@@ -52,11 +52,134 @@ struct QuorumAIOCB {
     int vote_ret;
 };
 
+/* Valid quorum resources look like
+ * quorum:threshold/total:path/to/image_1, ... ,path/to/image_total
+ *
+ * ',' is used as a separator to allow to use network path
+ * '\' is the escaping character for filename containing ','
+ */
+static int quorum_open(BlockDriverState *bs, const char *filename, int flags)
+{
+    BDRVQuorumState *s = bs->opaque;
+    int i, j, k, len, ret = 0;
+    char *a, *b, *names;
+    bool escape;
+
+    /* Parse the quorum: prefix */
+    if (strncmp(filename, "quorum:", strlen("quorum:"))) {
+        return -EINVAL;
+    }
+
+    filename += strlen("quorum:");
+
+    /* Get threshold */
+    errno = 0;
+    s->threshold = strtoul(filename, &a, 10);
+    if (*a != '/' || errno) {
+        return -EINVAL;
+    }
+    a++;
+
+    /* Get total */
+    errno = 0;
+    s->total = strtoul(a, &b, 10);
+    if (*b != ':' || errno) {
+        return -EINVAL;
+    }
+    b++;
+
+    if (s->threshold < 1 || s->total < 2) {
+        return -EINVAL;
+    }
+
+    if (s->threshold > s->total) {
+        return -EINVAL;
+    }
+
+    s->bs = g_malloc0(sizeof(BlockDriverState *) * s->total);
+    /* Two allocations for all filenames: simpler to free */
+    s->filenames = g_malloc0(sizeof(char *) * s->total);
+    names = g_strdup(b);
+
+    /* Get the filenames pointers */
+    escape = false;
+    s->filenames[0] = names;
+    len = strlen(names);
+    for (i = j = k = 0; i < len && j < s->total; i++) {
+        /* separation between two files */
+        if (!escape && names[i] == ',') {
+            char *prev = s->filenames[j];
+            prev[k] = '\0';
+            s->filenames[++j] = prev + k + 1;
+            k = 0;
+            continue;
+        }
+
+        escape = !escape && names[i] == '\\';
+
+        /* if we are not escaping copy */
+        if (!escape) {
+            s->filenames[j][k++] = names[i];
+        }
+    }
+    /* terminate last string */
+    s->filenames[j][k] = '\0';
+
+    if ((j + 1) != s->total) {
+        ret = -EINVAL;
+        goto free_exit;
+    }
+
+    /* Open files */
+    for (i = 0; i < s->total; i++) {
+        s->bs[i] = bdrv_new("");
+        ret = bdrv_open(s->bs[i], s->filenames[i], flags, NULL);
+        if (ret < 0) {
+            goto error_exit;
+        }
+    }
+
+    goto exit;
+
+error_exit:
+    for (; i >= 0; i--) {
+        bdrv_delete(s->bs[i]);
+        s->bs[i] = NULL;
+    }
+free_exit:
+    g_free(s->filenames[0]);
+    g_free(s->filenames);
+    s->filenames = NULL;
+    g_free(s->bs);
+exit:
+    return ret;
+}
+
+static void quorum_close(BlockDriverState *bs)
+{
+    BDRVQuorumState *s = bs->opaque;
+    int i;
+
+    for (i = 0; i < s->total; i++) {
+        /* Ensure writes reach stable storage */
+        bdrv_flush(s->bs[i]);
+        bdrv_delete(s->bs[i]);
+    }
+
+    g_free(s->filenames[0]);
+    g_free(s->filenames);
+    s->filenames = NULL;
+    g_free(s->bs);
+}
+
 static BlockDriver bdrv_quorum = {
     .format_name        = "quorum",
     .protocol_name      = "quorum",
 
     .instance_size      = sizeof(BDRVQuorumState),
+
+    .bdrv_file_open     = quorum_open,
+    .bdrv_close         = quorum_close,
 };
 
 static void bdrv_quorum_init(void)
-- 
1.7.9.5