Introduce Virtio-loopback epsilon release:

Epsilon release introduces a new compatibility layer which make virtio-loopback
design to work with QEMU and rust-vmm vhost-user backend without require any
changes.

Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
Change-Id: I52e57563e08a7d0bdc002f8e928ee61ba0c53dd9

1 files changed, 1688 insertions, 0 deletions

diff --git a/block/gluster.c b/block/gluster.c
new file mode 100644
index 000000000..398976bc6
--- /dev/null
+++ b/block/gluster.c
@@ -0,0 +1,1688 @@
+/*
+ * GlusterFS backend for QEMU
+ *
+ * Copyright (C) 2012 Bharata B Rao <bharata@linux.vnet.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/units.h"
+#include <glusterfs/api/glfs.h>
+#include "block/block_int.h"
+#include "block/qdict.h"
+#include "qapi/error.h"
+#include "qapi/qmp/qdict.h"
+#include "qapi/qmp/qerror.h"
+#include "qemu/uri.h"
+#include "qemu/error-report.h"
+#include "qemu/module.h"
+#include "qemu/option.h"
+#include "qemu/cutils.h"
+
+#ifdef CONFIG_GLUSTERFS_FTRUNCATE_HAS_STAT
+# define glfs_ftruncate(fd, offset) glfs_ftruncate(fd, offset, NULL, NULL)
+#endif
+
+#define GLUSTER_OPT_FILENAME        "filename"
+#define GLUSTER_OPT_VOLUME          "volume"
+#define GLUSTER_OPT_PATH            "path"
+#define GLUSTER_OPT_TYPE            "type"
+#define GLUSTER_OPT_SERVER_PATTERN  "server."
+#define GLUSTER_OPT_HOST            "host"
+#define GLUSTER_OPT_PORT            "port"
+#define GLUSTER_OPT_TO              "to"
+#define GLUSTER_OPT_IPV4            "ipv4"
+#define GLUSTER_OPT_IPV6            "ipv6"
+#define GLUSTER_OPT_SOCKET          "socket"
+#define GLUSTER_OPT_DEBUG           "debug"
+#define GLUSTER_DEFAULT_PORT        24007
+#define GLUSTER_DEBUG_DEFAULT       4
+#define GLUSTER_DEBUG_MAX           9
+#define GLUSTER_OPT_LOGFILE         "logfile"
+#define GLUSTER_LOGFILE_DEFAULT     "-" /* handled in libgfapi as /dev/stderr */
+/*
+ * Several versions of GlusterFS (3.12? -> 6.0.1) fail when the transfer size
+ * is greater or equal to 1024 MiB, so we are limiting the transfer size to 512
+ * MiB to avoid this rare issue.
+ */
+#define GLUSTER_MAX_TRANSFER        (512 * MiB)
+
+#define GERR_INDEX_HINT "hint: check in 'server' array index '%d'\n"
+
+typedef struct GlusterAIOCB {
+    int64_t size;
+    int ret;
+    Coroutine *coroutine;
+    AioContext *aio_context;
+} GlusterAIOCB;
+
+typedef struct BDRVGlusterState {
+    struct glfs *glfs;
+    struct glfs_fd *fd;
+    char *logfile;
+    bool supports_seek_data;
+    int debug;
+} BDRVGlusterState;
+
+typedef struct BDRVGlusterReopenState {
+    struct glfs *glfs;
+    struct glfs_fd *fd;
+} BDRVGlusterReopenState;
+
+
+typedef struct GlfsPreopened {
+    char *volume;
+    glfs_t *fs;
+    int ref;
+} GlfsPreopened;
+
+typedef struct ListElement {
+    QLIST_ENTRY(ListElement) list;
+    GlfsPreopened saved;
+} ListElement;
+
+static QLIST_HEAD(, ListElement) glfs_list;
+
+static QemuOptsList qemu_gluster_create_opts = {
+    .name = "qemu-gluster-create-opts",
+    .head = QTAILQ_HEAD_INITIALIZER(qemu_gluster_create_opts.head),
+    .desc = {
+        {
+            .name = BLOCK_OPT_SIZE,
+            .type = QEMU_OPT_SIZE,
+            .help = "Virtual disk size"
+        },
+        {
+            .name = BLOCK_OPT_PREALLOC,
+            .type = QEMU_OPT_STRING,
+            .help = "Preallocation mode (allowed values: off"
+#ifdef CONFIG_GLUSTERFS_FALLOCATE
+                    ", falloc"
+#endif
+#ifdef CONFIG_GLUSTERFS_ZEROFILL
+                    ", full"
+#endif
+                    ")"
+        },
+        {
+            .name = GLUSTER_OPT_DEBUG,
+            .type = QEMU_OPT_NUMBER,
+            .help = "Gluster log level, valid range is 0-9",
+        },
+        {
+            .name = GLUSTER_OPT_LOGFILE,
+            .type = QEMU_OPT_STRING,
+            .help = "Logfile path of libgfapi",
+        },
+        { /* end of list */ }
+    }
+};
+
+static QemuOptsList runtime_opts = {
+    .name = "gluster",
+    .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
+    .desc = {
+        {
+            .name = GLUSTER_OPT_FILENAME,
+            .type = QEMU_OPT_STRING,
+            .help = "URL to the gluster image",
+        },
+        {
+            .name = GLUSTER_OPT_DEBUG,
+            .type = QEMU_OPT_NUMBER,
+            .help = "Gluster log level, valid range is 0-9",
+        },
+        {
+            .name = GLUSTER_OPT_LOGFILE,
+            .type = QEMU_OPT_STRING,
+            .help = "Logfile path of libgfapi",
+        },
+        { /* end of list */ }
+    },
+};
+
+static QemuOptsList runtime_json_opts = {
+    .name = "gluster_json",
+    .head = QTAILQ_HEAD_INITIALIZER(runtime_json_opts.head),
+    .desc = {
+        {
+            .name = GLUSTER_OPT_VOLUME,
+            .type = QEMU_OPT_STRING,
+            .help = "name of gluster volume where VM image resides",
+        },
+        {
+            .name = GLUSTER_OPT_PATH,
+            .type = QEMU_OPT_STRING,
+            .help = "absolute path to image file in gluster volume",
+        },
+        {
+            .name = GLUSTER_OPT_DEBUG,
+            .type = QEMU_OPT_NUMBER,
+            .help = "Gluster log level, valid range is 0-9",
+        },
+        { /* end of list */ }
+    },
+};
+
+static QemuOptsList runtime_type_opts = {
+    .name = "gluster_type",
+    .head = QTAILQ_HEAD_INITIALIZER(runtime_type_opts.head),
+    .desc = {
+        {
+            .name = GLUSTER_OPT_TYPE,
+            .type = QEMU_OPT_STRING,
+            .help = "inet|unix",
+        },
+        { /* end of list */ }
+    },
+};
+
+static QemuOptsList runtime_unix_opts = {
+    .name = "gluster_unix",
+    .head = QTAILQ_HEAD_INITIALIZER(runtime_unix_opts.head),
+    .desc = {
+        {
+            .name = GLUSTER_OPT_SOCKET,
+            .type = QEMU_OPT_STRING,
+            .help = "socket file path (legacy)",
+        },
+        {
+            .name = GLUSTER_OPT_PATH,
+            .type = QEMU_OPT_STRING,
+            .help = "socket file path (QAPI)",
+        },
+        { /* end of list */ }
+    },
+};
+
+static QemuOptsList runtime_inet_opts = {
+    .name = "gluster_inet",
+    .head = QTAILQ_HEAD_INITIALIZER(runtime_inet_opts.head),
+    .desc = {
+        {
+            .name = GLUSTER_OPT_TYPE,
+            .type = QEMU_OPT_STRING,
+            .help = "inet|unix",
+        },
+        {
+            .name = GLUSTER_OPT_HOST,
+            .type = QEMU_OPT_STRING,
+            .help = "host address (hostname/ipv4/ipv6 addresses)",
+        },
+        {
+            .name = GLUSTER_OPT_PORT,
+            .type = QEMU_OPT_STRING,
+            .help = "port number on which glusterd is listening (default 24007)",
+        },
+        {
+            .name = "to",
+            .type = QEMU_OPT_NUMBER,
+            .help = "max port number, not supported by gluster",
+        },
+        {
+            .name = "ipv4",
+            .type = QEMU_OPT_BOOL,
+            .help = "ipv4 bool value, not supported by gluster",
+        },
+        {
+            .name = "ipv6",
+            .type = QEMU_OPT_BOOL,
+            .help = "ipv6 bool value, not supported by gluster",
+        },
+        { /* end of list */ }
+    },
+};
+
+static void glfs_set_preopened(const char *volume, glfs_t *fs)
+{
+    ListElement *entry = NULL;
+
+    entry = g_new(ListElement, 1);
+
+    entry->saved.volume = g_strdup(volume);
+
+    entry->saved.fs = fs;
+    entry->saved.ref = 1;
+
+    QLIST_INSERT_HEAD(&glfs_list, entry, list);
+}
+
+static glfs_t *glfs_find_preopened(const char *volume)
+{
+    ListElement *entry = NULL;
+
+     QLIST_FOREACH(entry, &glfs_list, list) {
+        if (strcmp(entry->saved.volume, volume) == 0) {
+            entry->saved.ref++;
+            return entry->saved.fs;
+        }
+     }
+
+    return NULL;
+}
+
+static void glfs_clear_preopened(glfs_t *fs)
+{
+    ListElement *entry = NULL;
+    ListElement *next;
+
+    if (fs == NULL) {
+        return;
+    }
+
+    QLIST_FOREACH_SAFE(entry, &glfs_list, list, next) {
+        if (entry->saved.fs == fs) {
+            if (--entry->saved.ref) {
+                return;
+            }
+
+            QLIST_REMOVE(entry, list);
+
+            glfs_fini(entry->saved.fs);
+            g_free(entry->saved.volume);
+            g_free(entry);
+        }
+    }
+}
+
+static int parse_volume_options(BlockdevOptionsGluster *gconf, char *path)
+{
+    char *p, *q;
+
+    if (!path) {
+        return -EINVAL;
+    }
+
+    /* volume */
+    p = q = path + strspn(path, "/");
+    p += strcspn(p, "/");
+    if (*p == '\0') {
+        return -EINVAL;
+    }
+    gconf->volume = g_strndup(q, p - q);
+
+    /* path */
+    p += strspn(p, "/");
+    if (*p == '\0') {
+        return -EINVAL;
+    }
+    gconf->path = g_strdup(p);
+    return 0;
+}
+
+/*
+ * file=gluster[+transport]://[host[:port]]/volume/path[?socket=...]
+ *
+ * 'gluster' is the protocol.
+ *
+ * 'transport' specifies the transport type used to connect to gluster
+ * management daemon (glusterd). Valid transport types are
+ * tcp or unix. If a transport type isn't specified, then tcp type is assumed.
+ *
+ * 'host' specifies the host where the volume file specification for
+ * the given volume resides. This can be either hostname or ipv4 address.
+ * If transport type is 'unix', then 'host' field should not be specified.
+ * The 'socket' field needs to be populated with the path to unix domain
+ * socket.
+ *
+ * 'port' is the port number on which glusterd is listening. This is optional
+ * and if not specified, QEMU will send 0 which will make gluster to use the
+ * default port. If the transport type is unix, then 'port' should not be
+ * specified.
+ *
+ * 'volume' is the name of the gluster volume which contains the VM image.
+ *
+ * 'path' is the path to the actual VM image that resides on gluster volume.
+ *
+ * Examples:
+ *
+ * file=gluster://1.2.3.4/testvol/a.img
+ * file=gluster+tcp://1.2.3.4/testvol/a.img
+ * file=gluster+tcp://1.2.3.4:24007/testvol/dir/a.img
+ * file=gluster+tcp://host.domain.com:24007/testvol/dir/a.img
+ * file=gluster+unix:///testvol/dir/a.img?socket=/tmp/glusterd.socket
+ */
+static int qemu_gluster_parse_uri(BlockdevOptionsGluster *gconf,
+                                  const char *filename)
+{
+    SocketAddress *gsconf;
+    URI *uri;
+    QueryParams *qp = NULL;
+    bool is_unix = false;
+    int ret = 0;
+
+    uri = uri_parse(filename);
+    if (!uri) {
+        return -EINVAL;
+    }
+
+    gsconf = g_new0(SocketAddress, 1);
+    QAPI_LIST_PREPEND(gconf->server, gsconf);
+
+    /* transport */
+    if (!uri->scheme || !strcmp(uri->scheme, "gluster")) {
+        gsconf->type = SOCKET_ADDRESS_TYPE_INET;
+    } else if (!strcmp(uri->scheme, "gluster+tcp")) {
+        gsconf->type = SOCKET_ADDRESS_TYPE_INET;
+    } else if (!strcmp(uri->scheme, "gluster+unix")) {
+        gsconf->type = SOCKET_ADDRESS_TYPE_UNIX;
+        is_unix = true;
+    } else if (!strcmp(uri->scheme, "gluster+rdma")) {
+        gsconf->type = SOCKET_ADDRESS_TYPE_INET;
+        warn_report("rdma feature is not supported, falling back to tcp");
+    } else {
+        ret = -EINVAL;
+        goto out;
+    }
+
+    ret = parse_volume_options(gconf, uri->path);
+    if (ret < 0) {
+        goto out;
+    }
+
+    qp = query_params_parse(uri->query);
+    if (qp->n > 1 || (is_unix && !qp->n) || (!is_unix && qp->n)) {
+        ret = -EINVAL;
+        goto out;
+    }
+
+    if (is_unix) {
+        if (uri->server || uri->port) {
+            ret = -EINVAL;
+            goto out;
+        }
+        if (strcmp(qp->p[0].name, "socket")) {
+            ret = -EINVAL;
+            goto out;
+        }
+        gsconf->u.q_unix.path = g_strdup(qp->p[0].value);
+    } else {
+        gsconf->u.inet.host = g_strdup(uri->server ? uri->server : "localhost");
+        if (uri->port) {
+            gsconf->u.inet.port = g_strdup_printf("%d", uri->port);
+        } else {
+            gsconf->u.inet.port = g_strdup_printf("%d", GLUSTER_DEFAULT_PORT);
+        }
+    }
+
+out:
+    if (qp) {
+        query_params_free(qp);
+    }
+    uri_free(uri);
+    return ret;
+}
+
+static struct glfs *qemu_gluster_glfs_init(BlockdevOptionsGluster *gconf,
+                                           Error **errp)
+{
+    struct glfs *glfs;
+    int ret;
+    int old_errno;
+    SocketAddressList *server;
+    unsigned long long port;
+
+    glfs = glfs_find_preopened(gconf->volume);
+    if (glfs) {
+        return glfs;
+    }
+
+    glfs = glfs_new(gconf->volume);
+    if (!glfs) {
+        goto out;
+    }
+
+    glfs_set_preopened(gconf->volume, glfs);
+
+    for (server = gconf->server; server; server = server->next) {
+        switch (server->value->type) {
+        case SOCKET_ADDRESS_TYPE_UNIX:
+            ret = glfs_set_volfile_server(glfs, "unix",
+                                   server->value->u.q_unix.path, 0);
+            break;
+        case SOCKET_ADDRESS_TYPE_INET:
+            if (parse_uint_full(server->value->u.inet.port, &port, 10) < 0 ||
+                port > 65535) {
+                error_setg(errp, "'%s' is not a valid port number",
+                           server->value->u.inet.port);
+                errno = EINVAL;
+                goto out;
+            }
+            ret = glfs_set_volfile_server(glfs, "tcp",
+                                   server->value->u.inet.host,
+                                   (int)port);
+            break;
+        case SOCKET_ADDRESS_TYPE_VSOCK:
+        case SOCKET_ADDRESS_TYPE_FD:
+        default:
+            abort();
+        }
+
+        if (ret < 0) {
+            goto out;
+        }
+    }
+
+    ret = glfs_set_logging(glfs, gconf->logfile, gconf->debug);
+    if (ret < 0) {
+        goto out;
+    }
+
+    ret = glfs_init(glfs);
+    if (ret) {
+        error_setg(errp, "Gluster connection for volume %s, path %s failed"
+                         " to connect", gconf->volume, gconf->path);
+        for (server = gconf->server; server; server = server->next) {
+            if (server->value->type  == SOCKET_ADDRESS_TYPE_UNIX) {
+                error_append_hint(errp, "hint: failed on socket %s ",
+                                  server->value->u.q_unix.path);
+            } else {
+                error_append_hint(errp, "hint: failed on host %s and port %s ",
+                                  server->value->u.inet.host,
+                                  server->value->u.inet.port);
+            }
+        }
+
+        error_append_hint(errp, "Please refer to gluster logs for more info\n");
+
+        /* glfs_init sometimes doesn't set errno although docs suggest that */
+        if (errno == 0) {
+            errno = EINVAL;
+        }
+
+        goto out;
+    }
+    return glfs;
+
+out:
+    if (glfs) {
+        old_errno = errno;
+        glfs_clear_preopened(glfs);
+        errno = old_errno;
+    }
+    return NULL;
+}
+
+/*
+ * Convert the json formatted command line into qapi.
+*/
+static int qemu_gluster_parse_json(BlockdevOptionsGluster *gconf,
+                                  QDict *options, Error **errp)
+{
+    QemuOpts *opts;
+    SocketAddress *gsconf = NULL;
+    SocketAddressList **tail;
+    QDict *backing_options = NULL;
+    Error *local_err = NULL;
+    char *str = NULL;
+    const char *ptr;
+    int i, type, num_servers;
+
+    /* create opts info from runtime_json_opts list */
+    opts = qemu_opts_create(&runtime_json_opts, NULL, 0, &error_abort);
+    if (!qemu_opts_absorb_qdict(opts, options, errp)) {
+        goto out;
+    }
+
+    num_servers = qdict_array_entries(options, GLUSTER_OPT_SERVER_PATTERN);
+    if (num_servers < 1) {
+        error_setg(&local_err, QERR_MISSING_PARAMETER, "server");
+        goto out;
+    }
+
+    ptr = qemu_opt_get(opts, GLUSTER_OPT_VOLUME);
+    if (!ptr) {
+        error_setg(&local_err, QERR_MISSING_PARAMETER, GLUSTER_OPT_VOLUME);
+        goto out;
+    }
+    gconf->volume = g_strdup(ptr);
+
+    ptr = qemu_opt_get(opts, GLUSTER_OPT_PATH);
+    if (!ptr) {
+        error_setg(&local_err, QERR_MISSING_PARAMETER, GLUSTER_OPT_PATH);
+        goto out;
+    }
+    gconf->path = g_strdup(ptr);
+    qemu_opts_del(opts);
+    tail = &gconf->server;
+
+    for (i = 0; i < num_servers; i++) {
+        str = g_strdup_printf(GLUSTER_OPT_SERVER_PATTERN"%d.", i);
+        qdict_extract_subqdict(options, &backing_options, str);
+
+        /* create opts info from runtime_type_opts list */
+        opts = qemu_opts_create(&runtime_type_opts, NULL, 0, &error_abort);
+        if (!qemu_opts_absorb_qdict(opts, backing_options, errp)) {
+            goto out;
+        }
+
+        ptr = qemu_opt_get(opts, GLUSTER_OPT_TYPE);
+        if (!ptr) {
+            error_setg(&local_err, QERR_MISSING_PARAMETER, GLUSTER_OPT_TYPE);
+            error_append_hint(&local_err, GERR_INDEX_HINT, i);
+            goto out;
+
+        }
+        gsconf = g_new0(SocketAddress, 1);
+        if (!strcmp(ptr, "tcp")) {
+            ptr = "inet";       /* accept legacy "tcp" */
+        }
+        type = qapi_enum_parse(&SocketAddressType_lookup, ptr, -1, NULL);
+        if (type != SOCKET_ADDRESS_TYPE_INET
+            && type != SOCKET_ADDRESS_TYPE_UNIX) {
+            error_setg(&local_err,
+                       "Parameter '%s' may be 'inet' or 'unix'",
+                       GLUSTER_OPT_TYPE);
+            error_append_hint(&local_err, GERR_INDEX_HINT, i);
+            goto out;
+        }
+        gsconf->type = type;
+        qemu_opts_del(opts);
+
+        if (gsconf->type == SOCKET_ADDRESS_TYPE_INET) {
+            /* create opts info from runtime_inet_opts list */
+            opts = qemu_opts_create(&runtime_inet_opts, NULL, 0, &error_abort);
+            if (!qemu_opts_absorb_qdict(opts, backing_options, errp)) {
+                goto out;
+            }
+
+            ptr = qemu_opt_get(opts, GLUSTER_OPT_HOST);
+            if (!ptr) {
+                error_setg(&local_err, QERR_MISSING_PARAMETER,
+                           GLUSTER_OPT_HOST);
+                error_append_hint(&local_err, GERR_INDEX_HINT, i);
+                goto out;
+            }
+            gsconf->u.inet.host = g_strdup(ptr);
+            ptr = qemu_opt_get(opts, GLUSTER_OPT_PORT);
+            if (!ptr) {
+                error_setg(&local_err, QERR_MISSING_PARAMETER,
+                           GLUSTER_OPT_PORT);
+                error_append_hint(&local_err, GERR_INDEX_HINT, i);
+                goto out;
+            }
+            gsconf->u.inet.port = g_strdup(ptr);
+
+            /* defend for unsupported fields in InetSocketAddress,
+             * i.e. @ipv4, @ipv6  and @to
+             */
+            ptr = qemu_opt_get(opts, GLUSTER_OPT_TO);
+            if (ptr) {
+                gsconf->u.inet.has_to = true;
+            }
+            ptr = qemu_opt_get(opts, GLUSTER_OPT_IPV4);
+            if (ptr) {
+                gsconf->u.inet.has_ipv4 = true;
+            }
+            ptr = qemu_opt_get(opts, GLUSTER_OPT_IPV6);
+            if (ptr) {
+                gsconf->u.inet.has_ipv6 = true;
+            }
+            if (gsconf->u.inet.has_to) {
+                error_setg(&local_err, "Parameter 'to' not supported");
+                goto out;
+            }
+            if (gsconf->u.inet.has_ipv4 || gsconf->u.inet.has_ipv6) {
+                error_setg(&local_err, "Parameters 'ipv4/ipv6' not supported");
+                goto out;
+            }
+            qemu_opts_del(opts);
+        } else {
+            /* create opts info from runtime_unix_opts list */
+            opts = qemu_opts_create(&runtime_unix_opts, NULL, 0, &error_abort);
+            if (!qemu_opts_absorb_qdict(opts, backing_options, errp)) {
+                goto out;
+            }
+
+            ptr = qemu_opt_get(opts, GLUSTER_OPT_PATH);
+            if (!ptr) {
+                ptr = qemu_opt_get(opts, GLUSTER_OPT_SOCKET);
+            } else if (qemu_opt_get(opts, GLUSTER_OPT_SOCKET)) {
+                error_setg(&local_err,
+                           "Conflicting parameters 'path' and 'socket'");
+                error_append_hint(&local_err, GERR_INDEX_HINT, i);
+                goto out;
+            }
+            if (!ptr) {
+                error_setg(&local_err, QERR_MISSING_PARAMETER,
+                           GLUSTER_OPT_PATH);
+                error_append_hint(&local_err, GERR_INDEX_HINT, i);
+                goto out;
+            }
+            gsconf->u.q_unix.path = g_strdup(ptr);
+            qemu_opts_del(opts);
+        }
+
+        QAPI_LIST_APPEND(tail, gsconf);
+        gsconf = NULL;
+
+        qobject_unref(backing_options);
+        backing_options = NULL;
+        g_free(str);
+        str = NULL;
+    }
+
+    return 0;
+
+out:
+    error_propagate(errp, local_err);
+    qapi_free_SocketAddress(gsconf);
+    qemu_opts_del(opts);
+    g_free(str);
+    qobject_unref(backing_options);
+    errno = EINVAL;
+    return -errno;
+}
+
+/* Converts options given in @filename and the @options QDict into the QAPI
+ * object @gconf. */
+static int qemu_gluster_parse(BlockdevOptionsGluster *gconf,
+                              const char *filename,
+                              QDict *options, Error **errp)
+{
+    int ret;
+    if (filename) {
+        ret = qemu_gluster_parse_uri(gconf, filename);
+        if (ret < 0) {
+            error_setg(errp, "invalid URI %s", filename);
+            error_append_hint(errp, "Usage: file=gluster[+transport]://"
+                                    "[host[:port]]volume/path[?socket=...]"
+                                    "[,file.debug=N]"
+                                    "[,file.logfile=/path/filename.log]\n");
+            return ret;
+        }
+    } else {
+        ret = qemu_gluster_parse_json(gconf, options, errp);
+        if (ret < 0) {
+            error_append_hint(errp, "Usage: "
+                             "-drive driver=qcow2,file.driver=gluster,"
+                             "file.volume=testvol,file.path=/path/a.qcow2"
+                             "[,file.debug=9]"
+                             "[,file.logfile=/path/filename.log],"
+                             "file.server.0.type=inet,"
+                             "file.server.0.host=1.2.3.4,"
+                             "file.server.0.port=24007,"
+                             "file.server.1.transport=unix,"
+                             "file.server.1.path=/var/run/glusterd.socket ..."
+                             "\n");
+            return ret;
+        }
+    }
+
+    return 0;
+}
+
+static struct glfs *qemu_gluster_init(BlockdevOptionsGluster *gconf,
+                                      const char *filename,
+                                      QDict *options, Error **errp)
+{
+    int ret;
+
+    ret = qemu_gluster_parse(gconf, filename, options, errp);
+    if (ret < 0) {
+        errno = -ret;
+        return NULL;
+    }
+
+    return qemu_gluster_glfs_init(gconf, errp);
+}
+
+/*
+ * AIO callback routine called from GlusterFS thread.
+ */
+static void gluster_finish_aiocb(struct glfs_fd *fd, ssize_t ret,
+#ifdef CONFIG_GLUSTERFS_IOCB_HAS_STAT
+                                 struct glfs_stat *pre, struct glfs_stat *post,
+#endif
+                                 void *arg)
+{
+    GlusterAIOCB *acb = (GlusterAIOCB *)arg;
+
+    if (!ret || ret == acb->size) {
+        acb->ret = 0; /* Success */
+    } else if (ret < 0) {
+        acb->ret = -errno; /* Read/Write failed */
+    } else {
+        acb->ret = -EIO; /* Partial read/write - fail it */
+    }
+
+    aio_co_schedule(acb->aio_context, acb->coroutine);
+}
+
+static void qemu_gluster_parse_flags(int bdrv_flags, int *open_flags)
+{
+    assert(open_flags != NULL);
+
+    *open_flags |= O_BINARY;
+
+    if (bdrv_flags & BDRV_O_RDWR) {
+        *open_flags |= O_RDWR;
+    } else {
+        *open_flags |= O_RDONLY;
+    }
+
+    if ((bdrv_flags & BDRV_O_NOCACHE)) {
+        *open_flags |= O_DIRECT;
+    }
+}
+
+/*
+ * Do SEEK_DATA/HOLE to detect if it is functional. Older broken versions of
+ * gfapi incorrectly return the current offset when SEEK_DATA/HOLE is used.
+ * - Corrected versions return -1 and set errno to EINVAL.
+ * - Versions that support SEEK_DATA/HOLE correctly, will return -1 and set
+ *   errno to ENXIO when SEEK_DATA is called with a position of EOF.
+ */
+static bool qemu_gluster_test_seek(struct glfs_fd *fd)
+{
+    off_t ret = 0;
+
+#if defined SEEK_HOLE && defined SEEK_DATA
+    off_t eof;
+
+    eof = glfs_lseek(fd, 0, SEEK_END);
+    if (eof < 0) {
+        /* this should never occur */
+        return false;
+    }
+
+    /* this should always fail with ENXIO if SEEK_DATA is supported */
+    ret = glfs_lseek(fd, eof, SEEK_DATA);
+#endif
+
+    return (ret < 0) && (errno == ENXIO);
+}
+
+static int qemu_gluster_open(BlockDriverState *bs,  QDict *options,
+                             int bdrv_flags, Error **errp)
+{
+    BDRVGlusterState *s = bs->opaque;
+    int open_flags = 0;
+    int ret = 0;
+    BlockdevOptionsGluster *gconf = NULL;
+    QemuOpts *opts;
+    const char *filename, *logfile;
+
+    opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
+    if (!qemu_opts_absorb_qdict(opts, options, errp)) {
+        ret = -EINVAL;
+        goto out;
+    }
+
+    filename = qemu_opt_get(opts, GLUSTER_OPT_FILENAME);
+
+    s->debug = qemu_opt_get_number(opts, GLUSTER_OPT_DEBUG,
+                                   GLUSTER_DEBUG_DEFAULT);
+    if (s->debug < 0) {
+        s->debug = 0;
+    } else if (s->debug > GLUSTER_DEBUG_MAX) {
+        s->debug = GLUSTER_DEBUG_MAX;
+    }
+
+    gconf = g_new0(BlockdevOptionsGluster, 1);
+    gconf->debug = s->debug;
+    gconf->has_debug = true;
+
+    logfile = qemu_opt_get(opts, GLUSTER_OPT_LOGFILE);
+    s->logfile = g_strdup(logfile ? logfile : GLUSTER_LOGFILE_DEFAULT);
+
+    gconf->logfile = g_strdup(s->logfile);
+    gconf->has_logfile = true;
+
+    s->glfs = qemu_gluster_init(gconf, filename, options, errp);
+    if (!s->glfs) {
+        ret = -errno;
+        goto out;
+    }
+
+#ifdef CONFIG_GLUSTERFS_XLATOR_OPT
+    /* Without this, if fsync fails for a recoverable reason (for instance,
+     * ENOSPC), gluster will dump its cache, preventing retries.  This means
+     * almost certain data loss.  Not all gluster versions support the
+     * 'resync-failed-syncs-after-fsync' key value, but there is no way to
+     * discover during runtime if it is supported (this api returns success for
+     * unknown key/value pairs) */
+    ret = glfs_set_xlator_option(s->glfs, "*-write-behind",
+                                          "resync-failed-syncs-after-fsync",
+                                          "on");
+    if (ret < 0) {
+        error_setg_errno(errp, errno, "Unable to set xlator key/value pair");
+        ret = -errno;
+        goto out;
+    }
+#endif
+
+    qemu_gluster_parse_flags(bdrv_flags, &open_flags);
+
+    s->fd = glfs_open(s->glfs, gconf->path, open_flags);
+    ret = s->fd ? 0 : -errno;
+
+    if (ret == -EACCES || ret == -EROFS) {
+        /* Try to degrade to read-only, but if it doesn't work, still use the
+         * normal error message. */
+        if (bdrv_apply_auto_read_only(bs, NULL, NULL) == 0) {
+            open_flags = (open_flags & ~O_RDWR) | O_RDONLY;
+            s->fd = glfs_open(s->glfs, gconf->path, open_flags);
+            ret = s->fd ? 0 : -errno;
+        }
+    }
+
+    s->supports_seek_data = qemu_gluster_test_seek(s->fd);
+
+out:
+    qemu_opts_del(opts);
+    qapi_free_BlockdevOptionsGluster(gconf);
+    if (!ret) {
+        return ret;
+    }
+    g_free(s->logfile);
+    if (s->fd) {
+        glfs_close(s->fd);
+    }
+
+    glfs_clear_preopened(s->glfs);
+
+    return ret;
+}
+
+static void qemu_gluster_refresh_limits(BlockDriverState *bs, Error **errp)
+{
+    bs->bl.max_transfer = GLUSTER_MAX_TRANSFER;
+    bs->bl.max_pdiscard = SIZE_MAX;
+}
+
+static int qemu_gluster_reopen_prepare(BDRVReopenState *state,
+                                       BlockReopenQueue *queue, Error **errp)
+{
+    int ret = 0;
+    BDRVGlusterState *s;
+    BDRVGlusterReopenState *reop_s;
+    BlockdevOptionsGluster *gconf;
+    int open_flags = 0;
+
+    assert(state != NULL);
+    assert(state->bs != NULL);
+
+    s = state->bs->opaque;
+
+    state->opaque = g_new0(BDRVGlusterReopenState, 1);
+    reop_s = state->opaque;
+
+    qemu_gluster_parse_flags(state->flags, &open_flags);
+
+    gconf = g_new0(BlockdevOptionsGluster, 1);
+    gconf->debug = s->debug;
+    gconf->has_debug = true;
+    gconf->logfile = g_strdup(s->logfile);
+    gconf->has_logfile = true;
+
+    /*
+     * If 'state->bs->exact_filename' is empty, 'state->options' should contain
+     * the JSON parameters already parsed.
+     */
+    if (state->bs->exact_filename[0] != '\0') {
+        reop_s->glfs = qemu_gluster_init(gconf, state->bs->exact_filename, NULL,
+                                         errp);
+    } else {
+        reop_s->glfs = qemu_gluster_init(gconf, NULL, state->options, errp);
+    }
+    if (reop_s->glfs == NULL) {
+        ret = -errno;
+        goto exit;
+    }
+
+#ifdef CONFIG_GLUSTERFS_XLATOR_OPT
+    ret = glfs_set_xlator_option(reop_s->glfs, "*-write-behind",
+                                 "resync-failed-syncs-after-fsync", "on");
+    if (ret < 0) {
+        error_setg_errno(errp, errno, "Unable to set xlator key/value pair");
+        ret = -errno;
+        goto exit;
+    }
+#endif
+
+    reop_s->fd = glfs_open(reop_s->glfs, gconf->path, open_flags);
+    if (reop_s->fd == NULL) {
+        /* reops->glfs will be cleaned up in _abort */
+        ret = -errno;
+        goto exit;
+    }
+
+exit:
+    /* state->opaque will be freed in either the _abort or _commit */
+    qapi_free_BlockdevOptionsGluster(gconf);
+    return ret;
+}
+
+static void qemu_gluster_reopen_commit(BDRVReopenState *state)
+{
+    BDRVGlusterReopenState *reop_s = state->opaque;
+    BDRVGlusterState *s = state->bs->opaque;
+
+
+    /* close the old */
+    if (s->fd) {
+        glfs_close(s->fd);
+    }
+
+    glfs_clear_preopened(s->glfs);
+
+    /* use the newly opened image / connection */
+    s->fd         = reop_s->fd;
+    s->glfs       = reop_s->glfs;
+
+    g_free(state->opaque);
+    state->opaque = NULL;
+
+    return;
+}
+
+
+static void qemu_gluster_reopen_abort(BDRVReopenState *state)
+{
+    BDRVGlusterReopenState *reop_s = state->opaque;
+
+    if (reop_s == NULL) {
+        return;
+    }
+
+    if (reop_s->fd) {
+        glfs_close(reop_s->fd);
+    }
+
+    glfs_clear_preopened(reop_s->glfs);
+
+    g_free(state->opaque);
+    state->opaque = NULL;
+
+    return;
+}
+
+#ifdef CONFIG_GLUSTERFS_ZEROFILL
+static coroutine_fn int qemu_gluster_co_pwrite_zeroes(BlockDriverState *bs,
+                                                      int64_t offset,
+                                                      int64_t bytes,
+                                                      BdrvRequestFlags flags)
+{
+    int ret;
+    GlusterAIOCB acb;
+    BDRVGlusterState *s = bs->opaque;
+
+    acb.size = bytes;
+    acb.ret = 0;
+    acb.coroutine = qemu_coroutine_self();
+    acb.aio_context = bdrv_get_aio_context(bs);
+
+    ret = glfs_zerofill_async(s->fd, offset, bytes, gluster_finish_aiocb, &acb);
+    if (ret < 0) {
+        return -errno;
+    }
+
+    qemu_coroutine_yield();
+    return acb.ret;
+}
+#endif
+
+static int qemu_gluster_do_truncate(struct glfs_fd *fd, int64_t offset,
+                                    PreallocMode prealloc, Error **errp)
+{
+    int64_t current_length;
+
+    current_length = glfs_lseek(fd, 0, SEEK_END);
+    if (current_length < 0) {
+        error_setg_errno(errp, errno, "Failed to determine current size");
+        return -errno;
+    }
+
+    if (current_length > offset && prealloc != PREALLOC_MODE_OFF) {
+        error_setg(errp, "Cannot use preallocation for shrinking files");
+        return -ENOTSUP;
+    }
+
+    if (current_length == offset) {
+        return 0;
+    }
+
+    switch (prealloc) {
+#ifdef CONFIG_GLUSTERFS_FALLOCATE
+    case PREALLOC_MODE_FALLOC:
+        if (glfs_fallocate(fd, 0, current_length, offset - current_length)) {
+            error_setg_errno(errp, errno, "Could not preallocate data");
+            return -errno;
+        }
+        break;
+#endif /* CONFIG_GLUSTERFS_FALLOCATE */
+#ifdef CONFIG_GLUSTERFS_ZEROFILL
+    case PREALLOC_MODE_FULL:
+        if (glfs_ftruncate(fd, offset)) {
+            error_setg_errno(errp, errno, "Could not resize file");
+            return -errno;
+        }
+        if (glfs_zerofill(fd, current_length, offset - current_length)) {
+            error_setg_errno(errp, errno, "Could not zerofill the new area");
+            return -errno;
+        }
+        break;
+#endif /* CONFIG_GLUSTERFS_ZEROFILL */
+    case PREALLOC_MODE_OFF:
+        if (glfs_ftruncate(fd, offset)) {
+            error_setg_errno(errp, errno, "Could not resize file");
+            return -errno;
+        }
+        break;
+    default:
+        error_setg(errp, "Unsupported preallocation mode: %s",
+                   PreallocMode_str(prealloc));
+        return -EINVAL;
+    }
+
+    return 0;
+}
+
+static int qemu_gluster_co_create(BlockdevCreateOptions *options,
+                                  Error **errp)
+{
+    BlockdevCreateOptionsGluster *opts = &options->u.gluster;
+    struct glfs *glfs;
+    struct glfs_fd *fd = NULL;
+    int ret = 0;
+
+    assert(options->driver == BLOCKDEV_DRIVER_GLUSTER);
+
+    glfs = qemu_gluster_glfs_init(opts->location, errp);
+    if (!glfs) {
+        ret = -errno;
+        goto out;
+    }
+
+    fd = glfs_creat(glfs, opts->location->path,
+                    O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, S_IRUSR | S_IWUSR);
+    if (!fd) {
+        ret = -errno;
+        goto out;
+    }
+
+    ret = qemu_gluster_do_truncate(fd, opts->size, opts->preallocation, errp);
+
+out:
+    if (fd) {
+        if (glfs_close(fd) != 0 && ret == 0) {
+            ret = -errno;
+        }
+    }
+    glfs_clear_preopened(glfs);
+    return ret;
+}
+
+static int coroutine_fn qemu_gluster_co_create_opts(BlockDriver *drv,
+                                                    const char *filename,
+                                                    QemuOpts *opts,
+                                                    Error **errp)
+{
+    BlockdevCreateOptions *options;
+    BlockdevCreateOptionsGluster *gopts;
+    BlockdevOptionsGluster *gconf;
+    char *tmp = NULL;
+    Error *local_err = NULL;
+    int ret;
+
+    options = g_new0(BlockdevCreateOptions, 1);
+    options->driver = BLOCKDEV_DRIVER_GLUSTER;
+    gopts = &options->u.gluster;
+
+    gconf = g_new0(BlockdevOptionsGluster, 1);
+    gopts->location = gconf;
+
+    gopts->size = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
+                           BDRV_SECTOR_SIZE);
+
+    tmp = qemu_opt_get_del(opts, BLOCK_OPT_PREALLOC);
+    gopts->preallocation = qapi_enum_parse(&PreallocMode_lookup, tmp,
+                                           PREALLOC_MODE_OFF, &local_err);
+    g_free(tmp);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        ret = -EINVAL;
+        goto fail;
+    }
+
+    gconf->debug = qemu_opt_get_number_del(opts, GLUSTER_OPT_DEBUG,
+                                           GLUSTER_DEBUG_DEFAULT);
+    if (gconf->debug < 0) {
+        gconf->debug = 0;
+    } else if (gconf->debug > GLUSTER_DEBUG_MAX) {
+        gconf->debug = GLUSTER_DEBUG_MAX;
+    }
+    gconf->has_debug = true;
+
+    gconf->logfile = qemu_opt_get_del(opts, GLUSTER_OPT_LOGFILE);
+    if (!gconf->logfile) {
+        gconf->logfile = g_strdup(GLUSTER_LOGFILE_DEFAULT);
+    }
+    gconf->has_logfile = true;
+
+    ret = qemu_gluster_parse(gconf, filename, NULL, errp);
+    if (ret < 0) {
+        goto fail;
+    }
+
+    ret = qemu_gluster_co_create(options, errp);
+    if (ret < 0) {
+        goto fail;
+    }
+
+    ret = 0;
+fail:
+    qapi_free_BlockdevCreateOptions(options);
+    return ret;
+}
+
+static coroutine_fn int qemu_gluster_co_rw(BlockDriverState *bs,
+                                           int64_t sector_num, int nb_sectors,
+                                           QEMUIOVector *qiov, int write)
+{
+    int ret;
+    GlusterAIOCB acb;
+    BDRVGlusterState *s = bs->opaque;
+    size_t size = nb_sectors * BDRV_SECTOR_SIZE;
+    off_t offset = sector_num * BDRV_SECTOR_SIZE;
+
+    acb.size = size;
+    acb.ret = 0;
+    acb.coroutine = qemu_coroutine_self();
+    acb.aio_context = bdrv_get_aio_context(bs);
+
+    if (write) {
+        ret = glfs_pwritev_async(s->fd, qiov->iov, qiov->niov, offset, 0,
+                                 gluster_finish_aiocb, &acb);
+    } else {
+        ret = glfs_preadv_async(s->fd, qiov->iov, qiov->niov, offset, 0,
+                                gluster_finish_aiocb, &acb);
+    }
+
+    if (ret < 0) {
+        return -errno;
+    }
+
+    qemu_coroutine_yield();
+    return acb.ret;
+}
+
+static coroutine_fn int qemu_gluster_co_truncate(BlockDriverState *bs,
+                                                 int64_t offset,
+                                                 bool exact,
+                                                 PreallocMode prealloc,
+                                                 BdrvRequestFlags flags,
+                                                 Error **errp)
+{
+    BDRVGlusterState *s = bs->opaque;
+    return qemu_gluster_do_truncate(s->fd, offset, prealloc, errp);
+}
+
+static coroutine_fn int qemu_gluster_co_readv(BlockDriverState *bs,
+                                              int64_t sector_num,
+                                              int nb_sectors,
+                                              QEMUIOVector *qiov)
+{
+    return qemu_gluster_co_rw(bs, sector_num, nb_sectors, qiov, 0);
+}
+
+static coroutine_fn int qemu_gluster_co_writev(BlockDriverState *bs,
+                                               int64_t sector_num,
+                                               int nb_sectors,
+                                               QEMUIOVector *qiov,
+                                               int flags)
+{
+    assert(!flags);
+    return qemu_gluster_co_rw(bs, sector_num, nb_sectors, qiov, 1);
+}
+
+static void qemu_gluster_close(BlockDriverState *bs)
+{
+    BDRVGlusterState *s = bs->opaque;
+
+    g_free(s->logfile);
+    if (s->fd) {
+        glfs_close(s->fd);
+        s->fd = NULL;
+    }
+    glfs_clear_preopened(s->glfs);
+}
+
+static coroutine_fn int qemu_gluster_co_flush_to_disk(BlockDriverState *bs)
+{
+    int ret;
+    GlusterAIOCB acb;
+    BDRVGlusterState *s = bs->opaque;
+
+    acb.size = 0;
+    acb.ret = 0;
+    acb.coroutine = qemu_coroutine_self();
+    acb.aio_context = bdrv_get_aio_context(bs);
+
+    ret = glfs_fsync_async(s->fd, gluster_finish_aiocb, &acb);
+    if (ret < 0) {
+        ret = -errno;
+        goto error;
+    }
+
+    qemu_coroutine_yield();
+    if (acb.ret < 0) {
+        ret = acb.ret;
+        goto error;
+    }
+
+    return acb.ret;
+
+error:
+    /* Some versions of Gluster (3.5.6 -> 3.5.8?) will not retain its cache
+     * after a fsync failure, so we have no way of allowing the guest to safely
+     * continue.  Gluster versions prior to 3.5.6 don't retain the cache
+     * either, but will invalidate the fd on error, so this is again our only
+     * option.
+     *
+     * The 'resync-failed-syncs-after-fsync' xlator option for the
+     * write-behind cache will cause later gluster versions to retain its
+     * cache after error, so long as the fd remains open.  However, we
+     * currently have no way of knowing if this option is supported.
+     *
+     * TODO: Once gluster provides a way for us to determine if the option
+     * is supported, bypass the closure and setting drv to NULL.  */
+    qemu_gluster_close(bs);
+    bs->drv = NULL;
+    return ret;
+}
+
+#ifdef CONFIG_GLUSTERFS_DISCARD
+static coroutine_fn int qemu_gluster_co_pdiscard(BlockDriverState *bs,
+                                                 int64_t offset, int64_t bytes)
+{
+    int ret;
+    GlusterAIOCB acb;
+    BDRVGlusterState *s = bs->opaque;
+
+    assert(bytes <= SIZE_MAX); /* rely on max_pdiscard */
+
+    acb.size = 0;
+    acb.ret = 0;
+    acb.coroutine = qemu_coroutine_self();
+    acb.aio_context = bdrv_get_aio_context(bs);
+
+    ret = glfs_discard_async(s->fd, offset, bytes, gluster_finish_aiocb, &acb);
+    if (ret < 0) {
+        return -errno;
+    }
+
+    qemu_coroutine_yield();
+    return acb.ret;
+}
+#endif
+
+static int64_t qemu_gluster_getlength(BlockDriverState *bs)
+{
+    BDRVGlusterState *s = bs->opaque;
+    int64_t ret;
+
+    ret = glfs_lseek(s->fd, 0, SEEK_END);
+    if (ret < 0) {
+        return -errno;
+    } else {
+        return ret;
+    }
+}
+
+static int64_t qemu_gluster_allocated_file_size(BlockDriverState *bs)
+{
+    BDRVGlusterState *s = bs->opaque;
+    struct stat st;
+    int ret;
+
+    ret = glfs_fstat(s->fd, &st);
+    if (ret < 0) {
+        return -errno;
+    } else {
+        return st.st_blocks * 512;
+    }
+}
+
+/*
+ * Find allocation range in @bs around offset @start.
+ * May change underlying file descriptor's file offset.
+ * If @start is not in a hole, store @start in @data, and the
+ * beginning of the next hole in @hole, and return 0.
+ * If @start is in a non-trailing hole, store @start in @hole and the
+ * beginning of the next non-hole in @data, and return 0.
+ * If @start is in a trailing hole or beyond EOF, return -ENXIO.
+ * If we can't find out, return a negative errno other than -ENXIO.
+ *
+ * (Shamefully copied from file-posix.c, only minuscule adaptions.)
+ */
+static int find_allocation(BlockDriverState *bs, off_t start,
+                           off_t *data, off_t *hole)
+{
+    BDRVGlusterState *s = bs->opaque;
+
+    if (!s->supports_seek_data) {
+        goto exit;
+    }
+
+#if defined SEEK_HOLE && defined SEEK_DATA
+    off_t offs;
+
+    /*
+     * SEEK_DATA cases:
+     * D1. offs == start: start is in data
+     * D2. offs > start: start is in a hole, next data at offs
+     * D3. offs < 0, errno = ENXIO: either start is in a trailing hole
+     *                              or start is beyond EOF
+     *     If the latter happens, the file has been truncated behind
+     *     our back since we opened it.  All bets are off then.
+     *     Treating like a trailing hole is simplest.
+     * D4. offs < 0, errno != ENXIO: we learned nothing
+     */
+    offs = glfs_lseek(s->fd, start, SEEK_DATA);
+    if (offs < 0) {
+        return -errno;          /* D3 or D4 */
+    }
+
+    if (offs < start) {
+        /* This is not a valid return by lseek().  We are safe to just return
+         * -EIO in this case, and we'll treat it like D4. Unfortunately some
+         *  versions of gluster server will return offs < start, so an assert
+         *  here will unnecessarily abort QEMU. */
+        return -EIO;
+    }
+
+    if (offs > start) {
+        /* D2: in hole, next data at offs */
+        *hole = start;
+        *data = offs;
+        return 0;
+    }
+
+    /* D1: in data, end not yet known */
+
+    /*
+     * SEEK_HOLE cases:
+     * H1. offs == start: start is in a hole
+     *     If this happens here, a hole has been dug behind our back
+     *     since the previous lseek().
+     * H2. offs > start: either start is in data, next hole at offs,
+     *                   or start is in trailing hole, EOF at offs
+     *     Linux treats trailing holes like any other hole: offs ==
+     *     start.  Solaris seeks to EOF instead: offs > start (blech).
+     *     If that happens here, a hole has been dug behind our back
+     *     since the previous lseek().
+     * H3. offs < 0, errno = ENXIO: start is beyond EOF
+     *     If this happens, the file has been truncated behind our
+     *     back since we opened it.  Treat it like a trailing hole.
+     * H4. offs < 0, errno != ENXIO: we learned nothing
+     *     Pretend we know nothing at all, i.e. "forget" about D1.
+     */
+    offs = glfs_lseek(s->fd, start, SEEK_HOLE);
+    if (offs < 0) {
+        return -errno;          /* D1 and (H3 or H4) */
+    }
+
+    if (offs < start) {
+        /* This is not a valid return by lseek().  We are safe to just return
+         * -EIO in this case, and we'll treat it like H4. Unfortunately some
+         *  versions of gluster server will return offs < start, so an assert
+         *  here will unnecessarily abort QEMU. */
+        return -EIO;
+    }
+
+    if (offs > start) {
+        /*
+         * D1 and H2: either in data, next hole at offs, or it was in
+         * data but is now in a trailing hole.  In the latter case,
+         * all bets are off.  Treating it as if it there was data all
+         * the way to EOF is safe, so simply do that.
+         */
+        *data = start;
+        *hole = offs;
+        return 0;
+    }
+
+    /* D1 and H1 */
+    return -EBUSY;
+#endif
+
+exit:
+    return -ENOTSUP;
+}
+
+/*
+ * Returns the allocation status of the specified offset.
+ *
+ * The block layer guarantees 'offset' and 'bytes' are within bounds.
+ *
+ * 'pnum' is set to the number of bytes (including and immediately following
+ * the specified offset) that are known to be in the same
+ * allocated/unallocated state.
+ *
+ * 'bytes' is a soft cap for 'pnum'.  If the information is free, 'pnum' may
+ * well exceed it.
+ *
+ * (Based on raw_co_block_status() from file-posix.c.)
+ */
+static int coroutine_fn qemu_gluster_co_block_status(BlockDriverState *bs,
+                                                     bool want_zero,
+                                                     int64_t offset,
+                                                     int64_t bytes,
+                                                     int64_t *pnum,
+                                                     int64_t *map,
+                                                     BlockDriverState **file)
+{
+    BDRVGlusterState *s = bs->opaque;
+    off_t data = 0, hole = 0;
+    int ret = -EINVAL;
+
+    assert(QEMU_IS_ALIGNED(offset | bytes, bs->bl.request_alignment));
+
+    if (!s->fd) {
+        return ret;
+    }
+
+    if (!want_zero) {
+        *pnum = bytes;
+        *map = offset;
+        *file = bs;
+        return BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID;
+    }
+
+    ret = find_allocation(bs, offset, &data, &hole);
+    if (ret == -ENXIO) {
+        /* Trailing hole */
+        *pnum = bytes;
+        ret = BDRV_BLOCK_ZERO;
+    } else if (ret < 0) {
+        /* No info available, so pretend there are no holes */
+        *pnum = bytes;
+        ret = BDRV_BLOCK_DATA;
+    } else if (data == offset) {
+        /* On a data extent, compute bytes to the end of the extent,
+         * possibly including a partial sector at EOF. */
+        *pnum = hole - offset;
+
+        /*
+         * We are not allowed to return partial sectors, though, so
+         * round up if necessary.
+         */
+        if (!QEMU_IS_ALIGNED(*pnum, bs->bl.request_alignment)) {
+            int64_t file_length = qemu_gluster_getlength(bs);
+            if (file_length > 0) {
+                /* Ignore errors, this is just a safeguard */
+                assert(hole == file_length);
+            }
+            *pnum = ROUND_UP(*pnum, bs->bl.request_alignment);
+        }
+
+        ret = BDRV_BLOCK_DATA;
+    } else {
+        /* On a hole, compute bytes to the beginning of the next extent.  */
+        assert(hole == offset);
+        *pnum = data - offset;
+        ret = BDRV_BLOCK_ZERO;
+    }
+
+    *map = offset;
+    *file = bs;
+
+    return ret | BDRV_BLOCK_OFFSET_VALID;
+}
+
+
+static const char *const gluster_strong_open_opts[] = {
+    GLUSTER_OPT_VOLUME,
+    GLUSTER_OPT_PATH,
+    GLUSTER_OPT_TYPE,
+    GLUSTER_OPT_SERVER_PATTERN,
+    GLUSTER_OPT_HOST,
+    GLUSTER_OPT_PORT,
+    GLUSTER_OPT_TO,
+    GLUSTER_OPT_IPV4,
+    GLUSTER_OPT_IPV6,
+    GLUSTER_OPT_SOCKET,
+
+    NULL
+};
+
+static BlockDriver bdrv_gluster = {
+    .format_name                  = "gluster",
+    .protocol_name                = "gluster",
+    .instance_size                = sizeof(BDRVGlusterState),
+    .bdrv_needs_filename          = false,
+    .bdrv_file_open               = qemu_gluster_open,
+    .bdrv_reopen_prepare          = qemu_gluster_reopen_prepare,
+    .bdrv_reopen_commit           = qemu_gluster_reopen_commit,
+    .bdrv_reopen_abort            = qemu_gluster_reopen_abort,
+    .bdrv_close                   = qemu_gluster_close,
+    .bdrv_co_create               = qemu_gluster_co_create,
+    .bdrv_co_create_opts          = qemu_gluster_co_create_opts,
+    .bdrv_getlength               = qemu_gluster_getlength,
+    .bdrv_get_allocated_file_size = qemu_gluster_allocated_file_size,
+    .bdrv_co_truncate             = qemu_gluster_co_truncate,
+    .bdrv_co_readv                = qemu_gluster_co_readv,
+    .bdrv_co_writev               = qemu_gluster_co_writev,
+    .bdrv_co_flush_to_disk        = qemu_gluster_co_flush_to_disk,
+#ifdef CONFIG_GLUSTERFS_DISCARD
+    .bdrv_co_pdiscard             = qemu_gluster_co_pdiscard,
+#endif
+#ifdef CONFIG_GLUSTERFS_ZEROFILL
+    .bdrv_co_pwrite_zeroes        = qemu_gluster_co_pwrite_zeroes,
+#endif
+    .bdrv_co_block_status         = qemu_gluster_co_block_status,
+    .bdrv_refresh_limits          = qemu_gluster_refresh_limits,
+    .create_opts                  = &qemu_gluster_create_opts,
+    .strong_runtime_opts          = gluster_strong_open_opts,
+};
+
+static BlockDriver bdrv_gluster_tcp = {
+    .format_name                  = "gluster",
+    .protocol_name                = "gluster+tcp",
+    .instance_size                = sizeof(BDRVGlusterState),
+    .bdrv_needs_filename          = false,
+    .bdrv_file_open               = qemu_gluster_open,
+    .bdrv_reopen_prepare          = qemu_gluster_reopen_prepare,
+    .bdrv_reopen_commit           = qemu_gluster_reopen_commit,
+    .bdrv_reopen_abort            = qemu_gluster_reopen_abort,
+    .bdrv_close                   = qemu_gluster_close,
+    .bdrv_co_create               = qemu_gluster_co_create,
+    .bdrv_co_create_opts          = qemu_gluster_co_create_opts,
+    .bdrv_getlength               = qemu_gluster_getlength,
+    .bdrv_get_allocated_file_size = qemu_gluster_allocated_file_size,
+    .bdrv_co_truncate             = qemu_gluster_co_truncate,
+    .bdrv_co_readv                = qemu_gluster_co_readv,
+    .bdrv_co_writev               = qemu_gluster_co_writev,
+    .bdrv_co_flush_to_disk        = qemu_gluster_co_flush_to_disk,
+#ifdef CONFIG_GLUSTERFS_DISCARD
+    .bdrv_co_pdiscard             = qemu_gluster_co_pdiscard,
+#endif
+#ifdef CONFIG_GLUSTERFS_ZEROFILL
+    .bdrv_co_pwrite_zeroes        = qemu_gluster_co_pwrite_zeroes,
+#endif
+    .bdrv_co_block_status         = qemu_gluster_co_block_status,
+    .bdrv_refresh_limits          = qemu_gluster_refresh_limits,
+    .create_opts                  = &qemu_gluster_create_opts,
+    .strong_runtime_opts          = gluster_strong_open_opts,
+};
+
+static BlockDriver bdrv_gluster_unix = {
+    .format_name                  = "gluster",
+    .protocol_name                = "gluster+unix",
+    .instance_size                = sizeof(BDRVGlusterState),
+    .bdrv_needs_filename          = true,
+    .bdrv_file_open               = qemu_gluster_open,
+    .bdrv_reopen_prepare          = qemu_gluster_reopen_prepare,
+    .bdrv_reopen_commit           = qemu_gluster_reopen_commit,
+    .bdrv_reopen_abort            = qemu_gluster_reopen_abort,
+    .bdrv_close                   = qemu_gluster_close,
+    .bdrv_co_create               = qemu_gluster_co_create,
+    .bdrv_co_create_opts          = qemu_gluster_co_create_opts,
+    .bdrv_getlength               = qemu_gluster_getlength,
+    .bdrv_get_allocated_file_size = qemu_gluster_allocated_file_size,
+    .bdrv_co_truncate             = qemu_gluster_co_truncate,
+    .bdrv_co_readv                = qemu_gluster_co_readv,
+    .bdrv_co_writev               = qemu_gluster_co_writev,
+    .bdrv_co_flush_to_disk        = qemu_gluster_co_flush_to_disk,
+#ifdef CONFIG_GLUSTERFS_DISCARD
+    .bdrv_co_pdiscard             = qemu_gluster_co_pdiscard,
+#endif
+#ifdef CONFIG_GLUSTERFS_ZEROFILL
+    .bdrv_co_pwrite_zeroes        = qemu_gluster_co_pwrite_zeroes,
+#endif
+    .bdrv_co_block_status         = qemu_gluster_co_block_status,
+    .bdrv_refresh_limits          = qemu_gluster_refresh_limits,
+    .create_opts                  = &qemu_gluster_create_opts,
+    .strong_runtime_opts          = gluster_strong_open_opts,
+};
+
+/* rdma is deprecated (actually never supported for volfile fetch).
+ * Let's maintain it for the protocol compatibility, to make sure things
+ * won't break immediately. For now, gluster+rdma will fall back to gluster+tcp
+ * protocol with a warning.
+ * TODO: remove gluster+rdma interface support
+ */
+static BlockDriver bdrv_gluster_rdma = {
+    .format_name                  = "gluster",
+    .protocol_name                = "gluster+rdma",
+    .instance_size                = sizeof(BDRVGlusterState),
+    .bdrv_needs_filename          = true,
+    .bdrv_file_open               = qemu_gluster_open,
+    .bdrv_reopen_prepare          = qemu_gluster_reopen_prepare,
+    .bdrv_reopen_commit           = qemu_gluster_reopen_commit,
+    .bdrv_reopen_abort            = qemu_gluster_reopen_abort,
+    .bdrv_close                   = qemu_gluster_close,
+    .bdrv_co_create               = qemu_gluster_co_create,
+    .bdrv_co_create_opts          = qemu_gluster_co_create_opts,
+    .bdrv_getlength               = qemu_gluster_getlength,
+    .bdrv_get_allocated_file_size = qemu_gluster_allocated_file_size,
+    .bdrv_co_truncate             = qemu_gluster_co_truncate,
+    .bdrv_co_readv                = qemu_gluster_co_readv,
+    .bdrv_co_writev               = qemu_gluster_co_writev,
+    .bdrv_co_flush_to_disk        = qemu_gluster_co_flush_to_disk,
+#ifdef CONFIG_GLUSTERFS_DISCARD
+    .bdrv_co_pdiscard             = qemu_gluster_co_pdiscard,
+#endif
+#ifdef CONFIG_GLUSTERFS_ZEROFILL
+    .bdrv_co_pwrite_zeroes        = qemu_gluster_co_pwrite_zeroes,
+#endif
+    .bdrv_co_block_status         = qemu_gluster_co_block_status,
+    .bdrv_refresh_limits          = qemu_gluster_refresh_limits,
+    .create_opts                  = &qemu_gluster_create_opts,
+    .strong_runtime_opts          = gluster_strong_open_opts,
+};
+
+static void bdrv_gluster_init(void)
+{
+    bdrv_register(&bdrv_gluster_rdma);
+    bdrv_register(&bdrv_gluster_unix);
+    bdrv_register(&bdrv_gluster_tcp);
+    bdrv_register(&bdrv_gluster);
+}
+
+block_init(bdrv_gluster_init);