[Qemu-devel] [PATCH V15 12/13] quorum: Add quorum_open() and quorum_close().

["Benoît Canet" <benoit.canet@irqsave.net>]

From: Benoît Canet <benoit@irqsave.net>

Example of command line:
-drive if=virtio,file.driver=quorum,\
file.children.0.file.filename=1.raw,\
file.children.0.node-name=1.raw,\
file.children.0.driver=raw,\
file.children.1.file.filename=2.raw,\
file.children.1.node-name=2.raw,\
file.children.1.driver=raw,\
file.children.2.file.filename=3.raw,\
file.children.2.node-name=3.raw,\
file.children.2.driver=raw,\
file.vote_threshold=2

file.blkverify=on with file.vote_threshold=2 and two files can be passed to
emulated blkverify.

Signed-off-by: Benoit Canet <benoit@irqsave.net>
---
 block/quorum.c   | 171 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 qapi-schema.json |  21 ++++++-
 2 files changed, 191 insertions(+), 1 deletion(-)

diff --git a/block/quorum.c b/block/quorum.c
index 1e683f8..d2bea29 100644
--- a/block/quorum.c
+++ b/block/quorum.c
@@ -17,8 +17,12 @@
 #include <gnutls/crypto.h>
 #include "block/block_int.h"
 #include "qapi/qmp/qjson.h"
+#include "qapi/qmp/types.h"
+#include "qemu-common.h"
 
 #define HASH_LENGTH 32
+#define KEY_PREFIX "children."
+#define KEY_FILENAME_SUFFIX ".file.filename"
 
 /* This union holds a vote hash value */
 typedef union QuorumVoteValue {
@@ -712,12 +716,179 @@ static bool quorum_recurse_is_first_non_filter(BlockDriverState *bs,
     return false;
 }
 
+static int quorum_valid_threshold(int threshold,
+                                  int total,
+                                  Error **errp)
+{
+
+    if (threshold < 1) {
+        error_set(errp, QERR_INVALID_PARAMETER_VALUE,
+                  "vote-threshold", "value >= 1");
+        return -ERANGE;
+    }
+
+    if (threshold > total) {
+        error_setg(errp, "threshold may not exceed children count");
+        return -ERANGE;
+    }
+
+    return 0;
+}
+
+static int quorum_open(BlockDriverState *bs,
+                       QDict *options,
+                       int flags,
+                       Error **errp)
+{
+    BDRVQuorumState *s = bs->opaque;
+    Error *local_err = NULL;
+    bool *opened;
+    QDict *sub = NULL;
+    QList *list = NULL;
+    const QListEntry *lentry;
+    const QDictEntry *dentry;
+    const char *value;
+    char *next;
+    int i;
+    int ret = 0;
+    unsigned long long threshold = 0;
+
+    qdict_flatten(options);
+    qdict_extract_subqdict(options, &sub, "children.");
+    qdict_array_split(sub, &list);
+
+    /* count how many different children are present and validate */
+    s->total = !qlist_size(list) ? qdict_size(sub) : qlist_size(list);
+    if (s->total < 2) {
+        error_setg(&local_err,
+                   "Number of provided children must be greater than 1");
+        ret = -EINVAL;
+        goto exit;
+    }
+
+    ret = qdict_get_try_int(options, "vote-threshold", -1);
+    /* from QMP */
+    if (ret != -1) {
+        qdict_del(options, "vote-threshold");
+        s->threshold = ret;
+    /* from command line */
+    } else {
+        /* retrieve the threshold option from the command line */
+        value = qdict_get_try_str(options, "vote_threshold");
+        if (!value) {
+            error_setg(&local_err,
+                       "vote_threshold must be provided");
+            ret = -EINVAL;
+            goto exit;
+        }
+        qdict_del(options, "vote_threshold");
+
+        ret = parse_uint(value, &threshold, &next, 10);
+
+        /* no int found -> scan fail */
+        if (ret < 0) {
+            error_setg(&local_err,
+                       "invalid vote_threshold specified");
+            ret = -EINVAL;
+            goto exit;
+        }
+        s->threshold = threshold;
+    }
+
+    /* and validate it against s->total */
+    ret = quorum_valid_threshold(s->threshold, s->total, &local_err);
+    if (ret < 0) {
+        goto exit;
+    }
+
+    /* is the driver in blkverify mode */
+    value = qdict_get_try_str(options, "blkverify");
+    if (value && !strcmp(value, "on")  &&
+        s->total == 2 && s->threshold == 2) {
+        s->is_blkverify = true;
+    } else if (value && strcmp(value, "off")) {
+        fprintf(stderr, "blkverify mode is set by setting blkverify=on "
+                        "and using two files with vote_threshold=2\n");
+    }
+    qdict_del(options, "blkverify");
+
+    /* allocate the children BlockDriverState array */
+    s->bs = g_new0(BlockDriverState *, s->total);
+    opened = g_new0(bool, s->total);
+
+    /* Open by file name or options dict (command line or QMP) */
+    if (s->total == qlist_size(list)) {
+        for (i = 0, lentry = qlist_first(list); lentry;
+            lentry = qlist_next(lentry), i++) {
+            ret = bdrv_open(&s->bs[i], NULL, NULL,
+                            qobject_to_qdict(lentry->value),
+                            flags, NULL, &local_err);
+            if (ret < 0) {
+                goto close_exit;
+            }
+            opened[i] = true;
+        }
+    /* Open by QMP references */
+    } else {
+        for (i = 0, dentry = qdict_first(sub); dentry;
+             dentry = qdict_next(sub, dentry), i++) {
+            ret = bdrv_open(&s->bs[i], NULL,
+                            qstring_get_str(qobject_to_qstring(dentry->value)),
+                            NULL, flags, NULL, &local_err);
+            if (ret < 0) {
+                goto close_exit;
+            }
+            opened[i] = true;
+        }
+    }
+
+    g_free(opened);
+    goto exit;
+
+close_exit:
+    /* cleanup on error */
+    for (i = 0; i < s->total; i++) {
+        if (!opened[i]) {
+            continue;
+        }
+        bdrv_unref(s->bs[i]);
+    }
+    g_free(s->bs);
+    g_free(opened);
+exit:
+    /* propagate error */
+    if (error_is_set(&local_err)) {
+        error_propagate(errp, local_err);
+    }
+    QDECREF(sub);
+    QDECREF(list);
+    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]);
+        /* close manually because we'll free s->bs */
+        bdrv_unref(s->bs[i]);
+    }
+
+    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,
+
     .bdrv_co_flush_to_disk = quorum_co_flush,
 
     .bdrv_getlength     = quorum_getlength,
diff --git a/qapi-schema.json b/qapi-schema.json
index 05ced9d..903a3a0 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -4352,6 +4352,24 @@
             'raw': 'BlockdevRef' } }
 
 ##
+# @BlockdevOptionsQuorum
+#
+# Driver specific block device options for Quorum
+#
+# @blkverify:      #optional true if the driver must print content mismatch
+#
+# @children:       the children block device to use
+#
+# @vote_threshold: the vote limit under which a read will fail
+#
+# Since: 2.0
+##
+{ 'type': 'BlockdevOptionsQuorum',
+  'data': { '*blkverify': 'bool',
+            'children': [ 'BlockdevRef' ],
+            'vote-threshold': 'int' } }
+
+##
 # @BlockdevOptions
 #
 # Options for creating a block device.
@@ -4389,7 +4407,8 @@
       'vdi':        'BlockdevOptionsGenericFormat',
       'vhdx':       'BlockdevOptionsGenericFormat',
       'vmdk':       'BlockdevOptionsGenericCOWFormat',
-      'vpc':        'BlockdevOptionsGenericFormat'
+      'vpc':        'BlockdevOptionsGenericFormat',
+      'quorum':     'BlockdevOptionsQuorum'
   } }
 
 ##
-- 
1.8.3.2