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, 910 insertions, 0 deletions

diff --git a/block/nfs.c b/block/nfs.c
new file mode 100644
index 000000000..577aea1d2
--- /dev/null
+++ b/block/nfs.c
@@ -0,0 +1,910 @@
+/*
+ * QEMU Block driver for native access to files on NFS shares
+ *
+ * Copyright (c) 2014-2017 Peter Lieven <pl@kamp.de>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu/osdep.h"
+
+#if !defined(_WIN32)
+#include <poll.h>
+#endif
+#include "qemu/config-file.h"
+#include "qemu/error-report.h"
+#include "qapi/error.h"
+#include "block/block_int.h"
+#include "block/qdict.h"
+#include "trace.h"
+#include "qemu/iov.h"
+#include "qemu/main-loop.h"
+#include "qemu/module.h"
+#include "qemu/option.h"
+#include "qemu/uri.h"
+#include "qemu/cutils.h"
+#include "sysemu/replay.h"
+#include "qapi/qapi-visit-block-core.h"
+#include "qapi/qmp/qdict.h"
+#include "qapi/qmp/qstring.h"
+#include "qapi/qobject-input-visitor.h"
+#include "qapi/qobject-output-visitor.h"
+#include <nfsc/libnfs.h>
+
+
+#define QEMU_NFS_MAX_READAHEAD_SIZE 1048576
+#define QEMU_NFS_MAX_PAGECACHE_SIZE (8388608 / NFS_BLKSIZE)
+#define QEMU_NFS_MAX_DEBUG_LEVEL 2
+
+typedef struct NFSClient {
+    struct nfs_context *context;
+    struct nfsfh *fh;
+    int events;
+    bool has_zero_init;
+    AioContext *aio_context;
+    QemuMutex mutex;
+    uint64_t st_blocks;
+    bool cache_used;
+    NFSServer *server;
+    char *path;
+    int64_t uid, gid, tcp_syncnt, readahead, pagecache, debug;
+} NFSClient;
+
+typedef struct NFSRPC {
+    BlockDriverState *bs;
+    int ret;
+    int complete;
+    QEMUIOVector *iov;
+    struct stat *st;
+    Coroutine *co;
+    NFSClient *client;
+} NFSRPC;
+
+static int nfs_parse_uri(const char *filename, QDict *options, Error **errp)
+{
+    URI *uri = NULL;
+    QueryParams *qp = NULL;
+    int ret = -EINVAL, i;
+
+    uri = uri_parse(filename);
+    if (!uri) {
+        error_setg(errp, "Invalid URI specified");
+        goto out;
+    }
+    if (g_strcmp0(uri->scheme, "nfs") != 0) {
+        error_setg(errp, "URI scheme must be 'nfs'");
+        goto out;
+    }
+
+    if (!uri->server) {
+        error_setg(errp, "missing hostname in URI");
+        goto out;
+    }
+
+    if (!uri->path) {
+        error_setg(errp, "missing file path in URI");
+        goto out;
+    }
+
+    qp = query_params_parse(uri->query);
+    if (!qp) {
+        error_setg(errp, "could not parse query parameters");
+        goto out;
+    }
+
+    qdict_put_str(options, "server.host", uri->server);
+    qdict_put_str(options, "server.type", "inet");
+    qdict_put_str(options, "path", uri->path);
+
+    for (i = 0; i < qp->n; i++) {
+        unsigned long long val;
+        if (!qp->p[i].value) {
+            error_setg(errp, "Value for NFS parameter expected: %s",
+                       qp->p[i].name);
+            goto out;
+        }
+        if (parse_uint_full(qp->p[i].value, &val, 0)) {
+            error_setg(errp, "Illegal value for NFS parameter: %s",
+                       qp->p[i].name);
+            goto out;
+        }
+        if (!strcmp(qp->p[i].name, "uid")) {
+            qdict_put_str(options, "user", qp->p[i].value);
+        } else if (!strcmp(qp->p[i].name, "gid")) {
+            qdict_put_str(options, "group", qp->p[i].value);
+        } else if (!strcmp(qp->p[i].name, "tcp-syncnt")) {
+            qdict_put_str(options, "tcp-syn-count", qp->p[i].value);
+        } else if (!strcmp(qp->p[i].name, "readahead")) {
+            qdict_put_str(options, "readahead-size", qp->p[i].value);
+        } else if (!strcmp(qp->p[i].name, "pagecache")) {
+            qdict_put_str(options, "page-cache-size", qp->p[i].value);
+        } else if (!strcmp(qp->p[i].name, "debug")) {
+            qdict_put_str(options, "debug", qp->p[i].value);
+        } else {
+            error_setg(errp, "Unknown NFS parameter name: %s",
+                       qp->p[i].name);
+            goto out;
+        }
+    }
+    ret = 0;
+out:
+    if (qp) {
+        query_params_free(qp);
+    }
+    uri_free(uri);
+    return ret;
+}
+
+static bool nfs_has_filename_options_conflict(QDict *options, Error **errp)
+{
+    const QDictEntry *qe;
+
+    for (qe = qdict_first(options); qe; qe = qdict_next(options, qe)) {
+        if (!strcmp(qe->key, "host") ||
+            !strcmp(qe->key, "path") ||
+            !strcmp(qe->key, "user") ||
+            !strcmp(qe->key, "group") ||
+            !strcmp(qe->key, "tcp-syn-count") ||
+            !strcmp(qe->key, "readahead-size") ||
+            !strcmp(qe->key, "page-cache-size") ||
+            !strcmp(qe->key, "debug") ||
+            strstart(qe->key, "server.", NULL))
+        {
+            error_setg(errp, "Option %s cannot be used with a filename",
+                       qe->key);
+            return true;
+        }
+    }
+
+    return false;
+}
+
+static void nfs_parse_filename(const char *filename, QDict *options,
+                               Error **errp)
+{
+    if (nfs_has_filename_options_conflict(options, errp)) {
+        return;
+    }
+
+    nfs_parse_uri(filename, options, errp);
+}
+
+static void nfs_process_read(void *arg);
+static void nfs_process_write(void *arg);
+
+/* Called with QemuMutex held.  */
+static void nfs_set_events(NFSClient *client)
+{
+    int ev = nfs_which_events(client->context);
+    if (ev != client->events) {
+        aio_set_fd_handler(client->aio_context, nfs_get_fd(client->context),
+                           false,
+                           (ev & POLLIN) ? nfs_process_read : NULL,
+                           (ev & POLLOUT) ? nfs_process_write : NULL,
+                           NULL, client);
+
+    }
+    client->events = ev;
+}
+
+static void nfs_process_read(void *arg)
+{
+    NFSClient *client = arg;
+
+    qemu_mutex_lock(&client->mutex);
+    nfs_service(client->context, POLLIN);
+    nfs_set_events(client);
+    qemu_mutex_unlock(&client->mutex);
+}
+
+static void nfs_process_write(void *arg)
+{
+    NFSClient *client = arg;
+
+    qemu_mutex_lock(&client->mutex);
+    nfs_service(client->context, POLLOUT);
+    nfs_set_events(client);
+    qemu_mutex_unlock(&client->mutex);
+}
+
+static void nfs_co_init_task(BlockDriverState *bs, NFSRPC *task)
+{
+    *task = (NFSRPC) {
+        .co             = qemu_coroutine_self(),
+        .bs             = bs,
+        .client         = bs->opaque,
+    };
+}
+
+static void nfs_co_generic_bh_cb(void *opaque)
+{
+    NFSRPC *task = opaque;
+
+    task->complete = 1;
+    aio_co_wake(task->co);
+}
+
+/* Called (via nfs_service) with QemuMutex held.  */
+static void
+nfs_co_generic_cb(int ret, struct nfs_context *nfs, void *data,
+                  void *private_data)
+{
+    NFSRPC *task = private_data;
+    task->ret = ret;
+    assert(!task->st);
+    if (task->ret > 0 && task->iov) {
+        if (task->ret <= task->iov->size) {
+            qemu_iovec_from_buf(task->iov, 0, data, task->ret);
+        } else {
+            task->ret = -EIO;
+        }
+    }
+    if (task->ret < 0) {
+        error_report("NFS Error: %s", nfs_get_error(nfs));
+    }
+    replay_bh_schedule_oneshot_event(task->client->aio_context,
+                                     nfs_co_generic_bh_cb, task);
+}
+
+static int coroutine_fn nfs_co_preadv(BlockDriverState *bs, int64_t offset,
+                                      int64_t bytes, QEMUIOVector *iov,
+                                      BdrvRequestFlags flags)
+{
+    NFSClient *client = bs->opaque;
+    NFSRPC task;
+
+    nfs_co_init_task(bs, &task);
+    task.iov = iov;
+
+    WITH_QEMU_LOCK_GUARD(&client->mutex) {
+        if (nfs_pread_async(client->context, client->fh,
+                            offset, bytes, nfs_co_generic_cb, &task) != 0) {
+            return -ENOMEM;
+        }
+
+        nfs_set_events(client);
+    }
+    while (!task.complete) {
+        qemu_coroutine_yield();
+    }
+
+    if (task.ret < 0) {
+        return task.ret;
+    }
+
+    /* zero pad short reads */
+    if (task.ret < iov->size) {
+        qemu_iovec_memset(iov, task.ret, 0, iov->size - task.ret);
+    }
+
+    return 0;
+}
+
+static int coroutine_fn nfs_co_pwritev(BlockDriverState *bs, int64_t offset,
+                                       int64_t bytes, QEMUIOVector *iov,
+                                       BdrvRequestFlags flags)
+{
+    NFSClient *client = bs->opaque;
+    NFSRPC task;
+    char *buf = NULL;
+    bool my_buffer = false;
+
+    nfs_co_init_task(bs, &task);
+
+    if (iov->niov != 1) {
+        buf = g_try_malloc(bytes);
+        if (bytes && buf == NULL) {
+            return -ENOMEM;
+        }
+        qemu_iovec_to_buf(iov, 0, buf, bytes);
+        my_buffer = true;
+    } else {
+        buf = iov->iov[0].iov_base;
+    }
+
+    WITH_QEMU_LOCK_GUARD(&client->mutex) {
+        if (nfs_pwrite_async(client->context, client->fh,
+                             offset, bytes, buf,
+                             nfs_co_generic_cb, &task) != 0) {
+            if (my_buffer) {
+                g_free(buf);
+            }
+            return -ENOMEM;
+        }
+
+        nfs_set_events(client);
+    }
+    while (!task.complete) {
+        qemu_coroutine_yield();
+    }
+
+    if (my_buffer) {
+        g_free(buf);
+    }
+
+    if (task.ret != bytes) {
+        return task.ret < 0 ? task.ret : -EIO;
+    }
+
+    return 0;
+}
+
+static int coroutine_fn nfs_co_flush(BlockDriverState *bs)
+{
+    NFSClient *client = bs->opaque;
+    NFSRPC task;
+
+    nfs_co_init_task(bs, &task);
+
+    WITH_QEMU_LOCK_GUARD(&client->mutex) {
+        if (nfs_fsync_async(client->context, client->fh, nfs_co_generic_cb,
+                            &task) != 0) {
+            return -ENOMEM;
+        }
+
+        nfs_set_events(client);
+    }
+    while (!task.complete) {
+        qemu_coroutine_yield();
+    }
+
+    return task.ret;
+}
+
+static void nfs_detach_aio_context(BlockDriverState *bs)
+{
+    NFSClient *client = bs->opaque;
+
+    aio_set_fd_handler(client->aio_context, nfs_get_fd(client->context),
+                       false, NULL, NULL, NULL, NULL);
+    client->events = 0;
+}
+
+static void nfs_attach_aio_context(BlockDriverState *bs,
+                                   AioContext *new_context)
+{
+    NFSClient *client = bs->opaque;
+
+    client->aio_context = new_context;
+    nfs_set_events(client);
+}
+
+static void nfs_client_close(NFSClient *client)
+{
+    if (client->context) {
+        qemu_mutex_lock(&client->mutex);
+        aio_set_fd_handler(client->aio_context, nfs_get_fd(client->context),
+                           false, NULL, NULL, NULL, NULL);
+        qemu_mutex_unlock(&client->mutex);
+        if (client->fh) {
+            nfs_close(client->context, client->fh);
+            client->fh = NULL;
+        }
+#ifdef LIBNFS_FEATURE_UMOUNT
+        nfs_umount(client->context);
+#endif
+        nfs_destroy_context(client->context);
+        client->context = NULL;
+    }
+    g_free(client->path);
+    qemu_mutex_destroy(&client->mutex);
+    qapi_free_NFSServer(client->server);
+    client->server = NULL;
+}
+
+static void nfs_file_close(BlockDriverState *bs)
+{
+    NFSClient *client = bs->opaque;
+    nfs_client_close(client);
+}
+
+static int64_t nfs_client_open(NFSClient *client, BlockdevOptionsNfs *opts,
+                               int flags, int open_flags, Error **errp)
+{
+    int64_t ret = -EINVAL;
+    struct stat st;
+    char *file = NULL, *strp = NULL;
+
+    qemu_mutex_init(&client->mutex);
+
+    client->path = g_strdup(opts->path);
+
+    strp = strrchr(client->path, '/');
+    if (strp == NULL) {
+        error_setg(errp, "Invalid URL specified");
+        goto fail;
+    }
+    file = g_strdup(strp);
+    *strp = 0;
+
+    /* Steal the NFSServer object from opts; set the original pointer to NULL
+     * to avoid use after free and double free. */
+    client->server = opts->server;
+    opts->server = NULL;
+
+    client->context = nfs_init_context();
+    if (client->context == NULL) {
+        error_setg(errp, "Failed to init NFS context");
+        goto fail;
+    }
+
+    if (opts->has_user) {
+        client->uid = opts->user;
+        nfs_set_uid(client->context, client->uid);
+    }
+
+    if (opts->has_group) {
+        client->gid = opts->group;
+        nfs_set_gid(client->context, client->gid);
+    }
+
+    if (opts->has_tcp_syn_count) {
+        client->tcp_syncnt = opts->tcp_syn_count;
+        nfs_set_tcp_syncnt(client->context, client->tcp_syncnt);
+    }
+
+#ifdef LIBNFS_FEATURE_READAHEAD
+    if (opts->has_readahead_size) {
+        if (open_flags & BDRV_O_NOCACHE) {
+            error_setg(errp, "Cannot enable NFS readahead "
+                             "if cache.direct = on");
+            goto fail;
+        }
+        client->readahead = opts->readahead_size;
+        if (client->readahead > QEMU_NFS_MAX_READAHEAD_SIZE) {
+            warn_report("Truncating NFS readahead size to %d",
+                        QEMU_NFS_MAX_READAHEAD_SIZE);
+            client->readahead = QEMU_NFS_MAX_READAHEAD_SIZE;
+        }
+        nfs_set_readahead(client->context, client->readahead);
+#ifdef LIBNFS_FEATURE_PAGECACHE
+        nfs_set_pagecache_ttl(client->context, 0);
+#endif
+        client->cache_used = true;
+    }
+#endif
+
+#ifdef LIBNFS_FEATURE_PAGECACHE
+    if (opts->has_page_cache_size) {
+        if (open_flags & BDRV_O_NOCACHE) {
+            error_setg(errp, "Cannot enable NFS pagecache "
+                             "if cache.direct = on");
+            goto fail;
+        }
+        client->pagecache = opts->page_cache_size;
+        if (client->pagecache > QEMU_NFS_MAX_PAGECACHE_SIZE) {
+            warn_report("Truncating NFS pagecache size to %d pages",
+                        QEMU_NFS_MAX_PAGECACHE_SIZE);
+            client->pagecache = QEMU_NFS_MAX_PAGECACHE_SIZE;
+        }
+        nfs_set_pagecache(client->context, client->pagecache);
+        nfs_set_pagecache_ttl(client->context, 0);
+        client->cache_used = true;
+    }
+#endif
+
+#ifdef LIBNFS_FEATURE_DEBUG
+    if (opts->has_debug) {
+        client->debug = opts->debug;
+        /* limit the maximum debug level to avoid potential flooding
+         * of our log files. */
+        if (client->debug > QEMU_NFS_MAX_DEBUG_LEVEL) {
+            warn_report("Limiting NFS debug level to %d",
+                        QEMU_NFS_MAX_DEBUG_LEVEL);
+            client->debug = QEMU_NFS_MAX_DEBUG_LEVEL;
+        }
+        nfs_set_debug(client->context, client->debug);
+    }
+#endif
+
+    ret = nfs_mount(client->context, client->server->host, client->path);
+    if (ret < 0) {
+        error_setg(errp, "Failed to mount nfs share: %s",
+                   nfs_get_error(client->context));
+        goto fail;
+    }
+
+    if (flags & O_CREAT) {
+        ret = nfs_creat(client->context, file, 0600, &client->fh);
+        if (ret < 0) {
+            error_setg(errp, "Failed to create file: %s",
+                       nfs_get_error(client->context));
+            goto fail;
+        }
+    } else {
+        ret = nfs_open(client->context, file, flags, &client->fh);
+        if (ret < 0) {
+            error_setg(errp, "Failed to open file : %s",
+                       nfs_get_error(client->context));
+            goto fail;
+        }
+    }
+
+    ret = nfs_fstat(client->context, client->fh, &st);
+    if (ret < 0) {
+        error_setg(errp, "Failed to fstat file: %s",
+                   nfs_get_error(client->context));
+        goto fail;
+    }
+
+    ret = DIV_ROUND_UP(st.st_size, BDRV_SECTOR_SIZE);
+#if !defined(_WIN32)
+    client->st_blocks = st.st_blocks;
+#endif
+    client->has_zero_init = S_ISREG(st.st_mode);
+    *strp = '/';
+    goto out;
+
+fail:
+    nfs_client_close(client);
+out:
+    g_free(file);
+    return ret;
+}
+
+static BlockdevOptionsNfs *nfs_options_qdict_to_qapi(QDict *options,
+                                                     Error **errp)
+{
+    BlockdevOptionsNfs *opts = NULL;
+    Visitor *v;
+    const QDictEntry *e;
+
+    v = qobject_input_visitor_new_flat_confused(options, errp);
+    if (!v) {
+        return NULL;
+    }
+
+    visit_type_BlockdevOptionsNfs(v, NULL, &opts, errp);
+    visit_free(v);
+    if (!opts) {
+        return NULL;
+    }
+
+    /* Remove the processed options from the QDict (the visitor processes
+     * _all_ options in the QDict) */
+    while ((e = qdict_first(options))) {
+        qdict_del(options, e->key);
+    }
+
+    return opts;
+}
+
+static int64_t nfs_client_open_qdict(NFSClient *client, QDict *options,
+                                     int flags, int open_flags, Error **errp)
+{
+    BlockdevOptionsNfs *opts;
+    int64_t ret;
+
+    opts = nfs_options_qdict_to_qapi(options, errp);
+    if (opts == NULL) {
+        ret = -EINVAL;
+        goto fail;
+    }
+
+    ret = nfs_client_open(client, opts, flags, open_flags, errp);
+fail:
+    qapi_free_BlockdevOptionsNfs(opts);
+    return ret;
+}
+
+static int nfs_file_open(BlockDriverState *bs, QDict *options, int flags,
+                         Error **errp) {
+    NFSClient *client = bs->opaque;
+    int64_t ret;
+
+    client->aio_context = bdrv_get_aio_context(bs);
+
+    ret = nfs_client_open_qdict(client, options,
+                                (flags & BDRV_O_RDWR) ? O_RDWR : O_RDONLY,
+                                bs->open_flags, errp);
+    if (ret < 0) {
+        return ret;
+    }
+
+    bs->total_sectors = ret;
+    if (client->has_zero_init) {
+        bs->supported_truncate_flags = BDRV_REQ_ZERO_WRITE;
+    }
+    return 0;
+}
+
+static QemuOptsList nfs_create_opts = {
+    .name = "nfs-create-opts",
+    .head = QTAILQ_HEAD_INITIALIZER(nfs_create_opts.head),
+    .desc = {
+        {
+            .name = BLOCK_OPT_SIZE,
+            .type = QEMU_OPT_SIZE,
+            .help = "Virtual disk size"
+        },
+        { /* end of list */ }
+    }
+};
+
+static int nfs_file_co_create(BlockdevCreateOptions *options, Error **errp)
+{
+    BlockdevCreateOptionsNfs *opts = &options->u.nfs;
+    NFSClient *client = g_new0(NFSClient, 1);
+    int ret;
+
+    assert(options->driver == BLOCKDEV_DRIVER_NFS);
+
+    client->aio_context = qemu_get_aio_context();
+
+    ret = nfs_client_open(client, opts->location, O_CREAT, 0, errp);
+    if (ret < 0) {
+        goto out;
+    }
+    ret = nfs_ftruncate(client->context, client->fh, opts->size);
+    nfs_client_close(client);
+
+out:
+    g_free(client);
+    return ret;
+}
+
+static int coroutine_fn nfs_file_co_create_opts(BlockDriver *drv,
+                                                const char *url,
+                                                QemuOpts *opts,
+                                                Error **errp)
+{
+    BlockdevCreateOptions *create_options;
+    BlockdevCreateOptionsNfs *nfs_opts;
+    QDict *options;
+    int ret;
+
+    create_options = g_new0(BlockdevCreateOptions, 1);
+    create_options->driver = BLOCKDEV_DRIVER_NFS;
+    nfs_opts = &create_options->u.nfs;
+
+    /* Read out options */
+    nfs_opts->size = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
+                              BDRV_SECTOR_SIZE);
+
+    options = qdict_new();
+    ret = nfs_parse_uri(url, options, errp);
+    if (ret < 0) {
+        goto out;
+    }
+
+    nfs_opts->location = nfs_options_qdict_to_qapi(options, errp);
+    if (nfs_opts->location == NULL) {
+        ret = -EINVAL;
+        goto out;
+    }
+
+    ret = nfs_file_co_create(create_options, errp);
+    if (ret < 0) {
+        goto out;
+    }
+
+    ret = 0;
+out:
+    qobject_unref(options);
+    qapi_free_BlockdevCreateOptions(create_options);
+    return ret;
+}
+
+static int nfs_has_zero_init(BlockDriverState *bs)
+{
+    NFSClient *client = bs->opaque;
+    return client->has_zero_init;
+}
+
+#if !defined(_WIN32)
+/* Called (via nfs_service) with QemuMutex held.  */
+static void
+nfs_get_allocated_file_size_cb(int ret, struct nfs_context *nfs, void *data,
+                               void *private_data)
+{
+    NFSRPC *task = private_data;
+    task->ret = ret;
+    if (task->ret == 0) {
+        memcpy(task->st, data, sizeof(struct stat));
+    }
+    if (task->ret < 0) {
+        error_report("NFS Error: %s", nfs_get_error(nfs));
+    }
+
+    /* Set task->complete before reading bs->wakeup.  */
+    qatomic_mb_set(&task->complete, 1);
+    bdrv_wakeup(task->bs);
+}
+
+static int64_t nfs_get_allocated_file_size(BlockDriverState *bs)
+{
+    NFSClient *client = bs->opaque;
+    NFSRPC task = {0};
+    struct stat st;
+
+    if (bdrv_is_read_only(bs) &&
+        !(bs->open_flags & BDRV_O_NOCACHE)) {
+        return client->st_blocks * 512;
+    }
+
+    task.bs = bs;
+    task.st = &st;
+    if (nfs_fstat_async(client->context, client->fh, nfs_get_allocated_file_size_cb,
+                        &task) != 0) {
+        return -ENOMEM;
+    }
+
+    nfs_set_events(client);
+    BDRV_POLL_WHILE(bs, !task.complete);
+
+    return (task.ret < 0 ? task.ret : st.st_blocks * 512);
+}
+#endif
+
+static int coroutine_fn
+nfs_file_co_truncate(BlockDriverState *bs, int64_t offset, bool exact,
+                     PreallocMode prealloc, BdrvRequestFlags flags,
+                     Error **errp)
+{
+    NFSClient *client = bs->opaque;
+    int ret;
+
+    if (prealloc != PREALLOC_MODE_OFF) {
+        error_setg(errp, "Unsupported preallocation mode '%s'",
+                   PreallocMode_str(prealloc));
+        return -ENOTSUP;
+    }
+
+    ret = nfs_ftruncate(client->context, client->fh, offset);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "Failed to truncate file");
+        return ret;
+    }
+
+    return 0;
+}
+
+/* Note that this will not re-establish a connection with the NFS server
+ * - it is effectively a NOP.  */
+static int nfs_reopen_prepare(BDRVReopenState *state,
+                              BlockReopenQueue *queue, Error **errp)
+{
+    NFSClient *client = state->bs->opaque;
+    struct stat st;
+    int ret = 0;
+
+    if (state->flags & BDRV_O_RDWR && bdrv_is_read_only(state->bs)) {
+        error_setg(errp, "Cannot open a read-only mount as read-write");
+        return -EACCES;
+    }
+
+    if ((state->flags & BDRV_O_NOCACHE) && client->cache_used) {
+        error_setg(errp, "Cannot disable cache if libnfs readahead or"
+                         " pagecache is enabled");
+        return -EINVAL;
+    }
+
+    /* Update cache for read-only reopens */
+    if (!(state->flags & BDRV_O_RDWR)) {
+        ret = nfs_fstat(client->context, client->fh, &st);
+        if (ret < 0) {
+            error_setg(errp, "Failed to fstat file: %s",
+                       nfs_get_error(client->context));
+            return ret;
+        }
+#if !defined(_WIN32)
+        client->st_blocks = st.st_blocks;
+#endif
+    }
+
+    return 0;
+}
+
+static void nfs_refresh_filename(BlockDriverState *bs)
+{
+    NFSClient *client = bs->opaque;
+
+    if (client->uid && !client->gid) {
+        snprintf(bs->exact_filename, sizeof(bs->exact_filename),
+                 "nfs://%s%s?uid=%" PRId64, client->server->host, client->path,
+                 client->uid);
+    } else if (!client->uid && client->gid) {
+        snprintf(bs->exact_filename, sizeof(bs->exact_filename),
+                 "nfs://%s%s?gid=%" PRId64, client->server->host, client->path,
+                 client->gid);
+    } else if (client->uid && client->gid) {
+        snprintf(bs->exact_filename, sizeof(bs->exact_filename),
+                 "nfs://%s%s?uid=%" PRId64 "&gid=%" PRId64,
+                 client->server->host, client->path, client->uid, client->gid);
+    } else {
+        snprintf(bs->exact_filename, sizeof(bs->exact_filename),
+                 "nfs://%s%s", client->server->host, client->path);
+    }
+}
+
+static char *nfs_dirname(BlockDriverState *bs, Error **errp)
+{
+    NFSClient *client = bs->opaque;
+
+    if (client->uid || client->gid) {
+        bdrv_refresh_filename(bs);
+        error_setg(errp, "Cannot generate a base directory for NFS node '%s'",
+                   bs->filename);
+        return NULL;
+    }
+
+    return g_strdup_printf("nfs://%s%s/", client->server->host, client->path);
+}
+
+#ifdef LIBNFS_FEATURE_PAGECACHE
+static void coroutine_fn nfs_co_invalidate_cache(BlockDriverState *bs,
+                                                 Error **errp)
+{
+    NFSClient *client = bs->opaque;
+    nfs_pagecache_invalidate(client->context, client->fh);
+}
+#endif
+
+static const char *nfs_strong_runtime_opts[] = {
+    "path",
+    "user",
+    "group",
+    "server.",
+
+    NULL
+};
+
+static BlockDriver bdrv_nfs = {
+    .format_name                    = "nfs",
+    .protocol_name                  = "nfs",
+
+    .instance_size                  = sizeof(NFSClient),
+    .bdrv_parse_filename            = nfs_parse_filename,
+    .create_opts                    = &nfs_create_opts,
+
+    .bdrv_has_zero_init             = nfs_has_zero_init,
+/* libnfs does not provide the allocated filesize of a file on win32. */
+#if !defined(_WIN32)
+    .bdrv_get_allocated_file_size   = nfs_get_allocated_file_size,
+#endif
+    .bdrv_co_truncate               = nfs_file_co_truncate,
+
+    .bdrv_file_open                 = nfs_file_open,
+    .bdrv_close                     = nfs_file_close,
+    .bdrv_co_create                 = nfs_file_co_create,
+    .bdrv_co_create_opts            = nfs_file_co_create_opts,
+    .bdrv_reopen_prepare            = nfs_reopen_prepare,
+
+    .bdrv_co_preadv                 = nfs_co_preadv,
+    .bdrv_co_pwritev                = nfs_co_pwritev,
+    .bdrv_co_flush_to_disk          = nfs_co_flush,
+
+    .bdrv_detach_aio_context        = nfs_detach_aio_context,
+    .bdrv_attach_aio_context        = nfs_attach_aio_context,
+    .bdrv_refresh_filename          = nfs_refresh_filename,
+    .bdrv_dirname                   = nfs_dirname,
+
+    .strong_runtime_opts            = nfs_strong_runtime_opts,
+
+#ifdef LIBNFS_FEATURE_PAGECACHE
+    .bdrv_co_invalidate_cache       = nfs_co_invalidate_cache,
+#endif
+};
+
+static void nfs_block_init(void)
+{
+    bdrv_register(&bdrv_nfs);
+}
+
+block_init(nfs_block_init);