[Qemu-block] [PATCH 06/16] quorum: allow ignoring child errors

[Wen Congyang]

If the child is not ready, read/write/getlength/flush will
return -errno. It is not critical error, and can be ignored:
1. read/write:
   Just not report the error event.
2. getlength:
   just ignore it. If all children's getlength return -errno,
   and be ignored, return -EIO.
3. flush:
   Just ignore it. If all children's getlength return -errno,
   and be ignored, return 0.

Usage: children.x.ignore-errors=true

Signed-off-by: Wen Congyang <address@hidden>
Signed-off-by: zhanghailiang <address@hidden>
Signed-off-by: Gonglei <address@hidden>
Cc: Alberto Garcia <address@hidden>
---
 block/quorum.c       | 94 ++++++++++++++++++++++++++++++++++++++++++++++++----
 qapi/block-core.json |  5 ++-
 2 files changed, 91 insertions(+), 8 deletions(-)

diff --git a/block/quorum.c b/block/quorum.c
index 8059861..f23dbb7 100644
--- a/block/quorum.c
+++ b/block/quorum.c
@@ -30,6 +30,7 @@
 #define QUORUM_OPT_BLKVERIFY      "blkverify"
 #define QUORUM_OPT_REWRITE        "rewrite-corrupted"
 #define QUORUM_OPT_READ_PATTERN   "read-pattern"
+#define QUORUM_CHILDREN_OPT_IGNORE_ERRORS   "ignore-errors"
 
 /* This union holds a vote hash value */
 typedef union QuorumVoteValue {
@@ -65,6 +66,7 @@ typedef struct QuorumVotes {
 /* the following structure holds the state of one quorum instance */
 typedef struct BDRVQuorumState {
     BlockDriverState **bs; /* children BlockDriverStates */
+    bool *ignore_errors;   /* ignore children's error? */
     int num_children;      /* children count */
     int max_children;      /* The maximum children count, we need to reallocate
                             * bs if num_children will larger than maximum.
@@ -100,6 +102,7 @@ typedef struct QuorumChildRequest {
     uint8_t *buf;
     int ret;
     QuorumAIOCB *parent;
+    int index;
 } QuorumChildRequest;
 
 /* Quorum will use the following structure to track progress of each read/write
@@ -212,6 +215,7 @@ static QuorumAIOCB *quorum_aio_get(BDRVQuorumState *s,
         acb->qcrs[i].buf = NULL;
         acb->qcrs[i].ret = 0;
         acb->qcrs[i].parent = acb;
+        acb->qcrs[i].index = i;
     }
 
     return acb;
@@ -305,7 +309,7 @@ static void quorum_aio_cb(void *opaque, int ret)
     acb->count++;
     if (ret == 0) {
         acb->success_count++;
-    } else {
+    } else if (!s->ignore_errors[sacb->index]) {
         quorum_report_bad(acb, sacb->aiocb->bs->node_name, ret);
     }
     assert(acb->count <= s->num_children);
@@ -716,19 +720,31 @@ static BlockAIOCB *quorum_aio_writev(BlockDriverState *bs,
 static int64_t quorum_getlength(BlockDriverState *bs)
 {
     BDRVQuorumState *s = bs->opaque;
-    int64_t result;
+    int64_t result = -EIO;
     int i;
 
     /* check that all file have the same length */
-    result = bdrv_getlength(s->bs[0]);
-    if (result < 0) {
-        return result;
-    }
-    for (i = 1; i < s->num_children; i++) {
+    for (i = 0; i < s->num_children; i++) {
         int64_t value = bdrv_getlength(s->bs[i]);
+
         if (value < 0) {
             return value;
         }
+
+        if (value == 0 && s->ignore_errors[i]) {
+            /*
+             * If the child is not ready, it cannot return -errno,
+             * otherwise refresh_total_sectors() will fail when
+             * we open the child.
+             */
+            continue;
+        }
+
+        if (result == -EIO) {
+            result = value;
+            continue;
+        }
+
         if (value != result) {
             return -EIO;
         }
@@ -766,6 +782,9 @@ static coroutine_fn int quorum_co_flush(BlockDriverState 
*bs)
 
     for (i = 0; i < s->num_children; i++) {
         result = bdrv_co_flush(s->bs[i]);
+        if (result < 0 && s->ignore_errors[i]) {
+            result = 0;
+        }
         result_value.l = result;
         quorum_count_vote(&error_votes, &result_value, i);
     }
@@ -840,6 +859,19 @@ static QemuOptsList quorum_runtime_opts = {
     },
 };
 
+static QemuOptsList quorum_children_common_opts = {
+    .name = "quorum children",
+    .head = QTAILQ_HEAD_INITIALIZER(quorum_children_common_opts.head),
+    .desc = {
+        {
+            .name = QUORUM_CHILDREN_OPT_IGNORE_ERRORS,
+            .type = QEMU_OPT_BOOL,
+            .help = "ignore child I/O error",
+        },
+        { /* end of list */ }
+    },
+};
+
 static int parse_read_pattern(const char *opt)
 {
     int i;
@@ -858,6 +890,37 @@ static int parse_read_pattern(const char *opt)
     return -EINVAL;
 }
 
+static int parse_children_options(BDRVQuorumState *s, QDict *options,
+                                  const char *indexstr, int index,
+                                  Error **errp)
+{
+    QemuOpts *children_opts = NULL;
+    Error *local_err = NULL;
+    int ret = 0;
+    bool value;
+
+    children_opts = qemu_opts_create(&quorum_children_common_opts, NULL, 0,
+                                     &error_abort);
+    qemu_opts_absorb_qdict_by_index(children_opts, options, indexstr,
+                                    &local_err);
+    if (local_err) {
+        ret = -EINVAL;
+        goto out;
+    }
+
+    value = qemu_opt_get_bool(children_opts, QUORUM_CHILDREN_OPT_IGNORE_ERRORS,
+                              false);
+    s->ignore_errors[index] = value;
+
+out:
+    qemu_opts_del(children_opts);
+    /* propagate error */
+    if (local_err) {
+        error_propagate(errp, local_err);
+    }
+    return ret;
+}
+
 static int quorum_open(BlockDriverState *bs, QDict *options, int flags,
                        Error **errp)
 {
@@ -929,12 +992,18 @@ static int quorum_open(BlockDriverState *bs, QDict 
*options, int flags,
     s->bs = g_new0(BlockDriverState *, s->num_children);
     opened = g_new0(bool, s->num_children);
     s->max_children = s->num_children;
+    s->ignore_errors = g_new0(bool, s->num_children);
 
     for (i = 0; i < s->num_children; i++) {
         char indexstr[32];
         ret = snprintf(indexstr, 32, "children.%d", i);
         assert(ret < 32);
 
+        ret = parse_children_options(s, options, indexstr, i, &local_err);
+        if (ret < 0) {
+            goto close_exit;
+        }
+
         ret = bdrv_open_image(&s->bs[i], NULL, options, indexstr, bs,
                               &child_format, false, &local_err);
         if (ret < 0) {
@@ -976,6 +1045,7 @@ static void quorum_close(BlockDriverState *bs)
     }
 
     g_free(s->bs);
+    g_free(s->ignore_errors);
 }
 
 static void quorum_detach_aio_context(BlockDriverState *bs)
@@ -1014,10 +1084,18 @@ static void quorum_add_child(BlockDriverState *bs, 
QDict *options, Error **errp)
         }
 
         s->bs = g_renew(BlockDriverState *, s->bs, s->max_children + 1);
+        s->ignore_errors = g_renew(bool, s->ignore_errors, s->max_children + 
1);
         s->bs[s->num_children] = NULL;
         s->max_children += 1;
     }
 
+    ret = parse_children_options(s, options, "child", s->num_children,
+                                 &local_err);
+    if (ret < 0) {
+        error_propagate(errp, local_err);
+        return;
+    }
+
     ret = bdrv_open_image(&s->bs[s->num_children], NULL, options, "child", bs,
                           &child_format, false, &local_err);
     if (ret < 0) {
@@ -1058,6 +1136,8 @@ static void quorum_del_child(BlockDriverState *bs, 
BlockDriverState *child_bs,
     bdrv_drain(bs);
     /* We can safely remove this child now */
     memmove(&s->bs[i], &s->bs[i+1], (s->num_children - i - 1) * sizeof(void 
*));
+    memmove(&s->ignore_errors[i], &s->ignore_errors[i+1],
+            (s->num_children - i - 1) * sizeof(bool));
     s->num_children--;
     s->bs[s->num_children] = NULL;
     bdrv_unref(child_bs);
diff --git a/qapi/block-core.json b/qapi/block-core.json
index bf141a2..24099ef 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1411,6 +1411,8 @@
 # @allow-write-backing-file: #optional whether the backing file is opened in
 #                            read-write mode. It is only for backing file
 #                            (Since 2.5 default: false)
+# @ignore-errors: #options whether the child's I/O error should be ignored.
+#                 it is only for quorum's child.(Since 2.5 default: false)
 #
 # Since: 1.7
 ##
@@ -1425,7 +1427,8 @@
             '*werror': 'BlockdevOnError',
             '*read-only': 'bool',
             '*detect-zeroes': 'BlockdevDetectZeroesOptions',
-            '*allow-write-backing-file': 'bool' } }
+            '*allow-write-backing-file': 'bool',
+            '*ignore-errors': 'bool' } }
 
 ##
 # @BlockdevOptionsFile
-- 
2.4.3