block: add native support for NFS

This patch adds native support for accessing images on NFS
shares without the requirement to actually mount the entire
NFS share on the host.

NFS Images can simply be specified by an url of the form:
nfs://<host>/<export>/<filename>[?param=value[&param2=value2[&...]]]

For example:
qemu-img create -f qcow2 nfs://10.0.0.1/qemu-images/test.qcow2

You need LibNFS from Ronnie Sahlberg available at:
   git://github.com/sahlberg/libnfs.git
for this to work.

During configure it is automatically probed for libnfs and support
is enabled on-the-fly. You can forbid or enforce libnfs support
with --disable-libnfs or --enable-libnfs respectively.

Due to NFS restrictions you might need to execute your binaries
as root, allow them to open priviledged ports (<1024) or specify
insecure option on the NFS server.

For additional information on ROOT vs. non-ROOT operation and URL
format + parameters see:
   https://raw.github.com/sahlberg/libnfs/master/README

Supported by qemu are the uid, gid and tcp-syncnt URL parameters.

LibNFS currently support NFS version 3 only.

Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 439 insertions, 0 deletions

diff --git a/block/nfs.c b/block/nfs.c
new file mode 100644
index 0000000000..ef731f04e3
--- /dev/null
+++ b/block/nfs.c
@@ -0,0 +1,439 @@
+/*
+ * QEMU Block driver for native access to files on NFS shares
+ *
+ * Copyright (c) 2014 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 "config-host.h"
+
+#include <poll.h>
+#include "qemu-common.h"
+#include "qemu/config-file.h"
+#include "qemu/error-report.h"
+#include "block/block_int.h"
+#include "trace.h"
+#include "qemu/iov.h"
+#include "qemu/uri.h"
+#include "sysemu/sysemu.h"
+#include <nfsc/libnfs.h>
+
+typedef struct NFSClient {
+    struct nfs_context *context;
+    struct nfsfh *fh;
+    int events;
+    bool has_zero_init;
+} NFSClient;
+
+typedef struct NFSRPC {
+    int ret;
+    int complete;
+    QEMUIOVector *iov;
+    struct stat *st;
+    Coroutine *co;
+    QEMUBH *bh;
+} NFSRPC;
+
+static void nfs_process_read(void *arg);
+static void nfs_process_write(void *arg);
+
+static void nfs_set_events(NFSClient *client)
+{
+    int ev = nfs_which_events(client->context);
+    if (ev != client->events) {
+        qemu_aio_set_fd_handler(nfs_get_fd(client->context),
+                      (ev & POLLIN) ? nfs_process_read : NULL,
+                      (ev & POLLOUT) ? nfs_process_write : NULL,
+                      client);
+
+    }
+    client->events = ev;
+}
+
+static void nfs_process_read(void *arg)
+{
+    NFSClient *client = arg;
+    nfs_service(client->context, POLLIN);
+    nfs_set_events(client);
+}
+
+static void nfs_process_write(void *arg)
+{
+    NFSClient *client = arg;
+    nfs_service(client->context, POLLOUT);
+    nfs_set_events(client);
+}
+
+static void nfs_co_init_task(NFSClient *client, NFSRPC *task)
+{
+    *task = (NFSRPC) {
+        .co         = qemu_coroutine_self(),
+    };
+}
+
+static void nfs_co_generic_bh_cb(void *opaque)
+{
+    NFSRPC *task = opaque;
+    qemu_bh_delete(task->bh);
+    qemu_coroutine_enter(task->co, NULL);
+}
+
+static void
+nfs_co_generic_cb(int ret, struct nfs_context *nfs, void *data,
+                  void *private_data)
+{
+    NFSRPC *task = private_data;
+    task->complete = 1;
+    task->ret = ret;
+    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 && task->st) {
+        memcpy(task->st, data, sizeof(struct stat));
+    }
+    if (task->co) {
+        task->bh = qemu_bh_new(nfs_co_generic_bh_cb, task);
+        qemu_bh_schedule(task->bh);
+    }
+}
+
+static int coroutine_fn nfs_co_readv(BlockDriverState *bs,
+                                     int64_t sector_num, int nb_sectors,
+                                     QEMUIOVector *iov)
+{
+    NFSClient *client = bs->opaque;
+    NFSRPC task;
+
+    nfs_co_init_task(client, &task);
+    task.iov = iov;
+
+    if (nfs_pread_async(client->context, client->fh,
+                        sector_num * BDRV_SECTOR_SIZE,
+                        nb_sectors * BDRV_SECTOR_SIZE,
+                        nfs_co_generic_cb, &task) != 0) {
+        return -ENOMEM;
+    }
+
+    while (!task.complete) {
+        nfs_set_events(client);
+        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_writev(BlockDriverState *bs,
+                                        int64_t sector_num, int nb_sectors,
+                                        QEMUIOVector *iov)
+{
+    NFSClient *client = bs->opaque;
+    NFSRPC task;
+    char *buf = NULL;
+
+    nfs_co_init_task(client, &task);
+
+    buf = g_malloc(nb_sectors * BDRV_SECTOR_SIZE);
+    qemu_iovec_to_buf(iov, 0, buf, nb_sectors * BDRV_SECTOR_SIZE);
+
+    if (nfs_pwrite_async(client->context, client->fh,
+                         sector_num * BDRV_SECTOR_SIZE,
+                         nb_sectors * BDRV_SECTOR_SIZE,
+                         buf, nfs_co_generic_cb, &task) != 0) {
+        g_free(buf);
+        return -ENOMEM;
+    }
+
+    while (!task.complete) {
+        nfs_set_events(client);
+        qemu_coroutine_yield();
+    }
+
+    g_free(buf);
+
+    if (task.ret != nb_sectors * BDRV_SECTOR_SIZE) {
+        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(client, &task);
+
+    if (nfs_fsync_async(client->context, client->fh, nfs_co_generic_cb,
+                        &task) != 0) {
+        return -ENOMEM;
+    }
+
+    while (!task.complete) {
+        nfs_set_events(client);
+        qemu_coroutine_yield();
+    }
+
+    return task.ret;
+}
+
+/* TODO Convert to fine grained options */
+static QemuOptsList runtime_opts = {
+    .name = "nfs",
+    .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
+    .desc = {
+        {
+            .name = "filename",
+            .type = QEMU_OPT_STRING,
+            .help = "URL to the NFS file",
+        },
+        { /* end of list */ }
+    },
+};
+
+static void nfs_client_close(NFSClient *client)
+{
+    if (client->context) {
+        if (client->fh) {
+            nfs_close(client->context, client->fh);
+        }
+        qemu_aio_set_fd_handler(nfs_get_fd(client->context), NULL, NULL, NULL);
+        nfs_destroy_context(client->context);
+    }
+    memset(client, 0, sizeof(NFSClient));
+}
+
+static void nfs_file_close(BlockDriverState *bs)
+{
+    NFSClient *client = bs->opaque;
+    nfs_client_close(client);
+}
+
+static int64_t nfs_client_open(NFSClient *client, const char *filename,
+                               int flags, Error **errp)
+{
+    int ret = -EINVAL, i;
+    struct stat st;
+    URI *uri;
+    QueryParams *qp = NULL;
+    char *file = NULL, *strp = NULL;
+
+    uri = uri_parse(filename);
+    if (!uri) {
+        error_setg(errp, "Invalid URL specified");
+        goto fail;
+    }
+    strp = strrchr(uri->path, '/');
+    if (strp == NULL) {
+        error_setg(errp, "Invalid URL specified");
+        goto fail;
+    }
+    file = g_strdup(strp);
+    *strp = 0;
+
+    client->context = nfs_init_context();
+    if (client->context == NULL) {
+        error_setg(errp, "Failed to init NFS context");
+        goto fail;
+    }
+
+    qp = query_params_parse(uri->query);
+    for (i = 0; i < qp->n; i++) {
+        if (!qp->p[i].value) {
+            error_setg(errp, "Value for NFS parameter expected: %s",
+                       qp->p[i].name);
+            goto fail;
+        }
+        if (!strncmp(qp->p[i].name, "uid", 3)) {
+            nfs_set_uid(client->context, atoi(qp->p[i].value));
+        } else if (!strncmp(qp->p[i].name, "gid", 3)) {
+            nfs_set_gid(client->context, atoi(qp->p[i].value));
+        } else if (!strncmp(qp->p[i].name, "tcp-syncnt", 10)) {
+            nfs_set_tcp_syncnt(client->context, atoi(qp->p[i].value));
+        } else {
+            error_setg(errp, "Unknown NFS parameter name: %s",
+                       qp->p[i].name);
+            goto fail;
+        }
+    }
+
+    ret = nfs_mount(client->context, uri->server, uri->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);
+    client->has_zero_init = S_ISREG(st.st_mode);
+    goto out;
+fail:
+    nfs_client_close(client);
+out:
+    if (qp) {
+        query_params_free(qp);
+    }
+    uri_free(uri);
+    g_free(file);
+    return ret;
+}
+
+static int nfs_file_open(BlockDriverState *bs, QDict *options, int flags,
+                         Error **errp) {
+    NFSClient *client = bs->opaque;
+    int64_t ret;
+    QemuOpts *opts;
+    Error *local_err = NULL;
+
+    opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
+    qemu_opts_absorb_qdict(opts, options, &local_err);
+    if (error_is_set(&local_err)) {
+        error_propagate(errp, local_err);
+        return -EINVAL;
+    }
+    ret = nfs_client_open(client, qemu_opt_get(opts, "filename"),
+                          (flags & BDRV_O_RDWR) ? O_RDWR : O_RDONLY,
+                          errp);
+    if (ret < 0) {
+        return ret;
+    }
+    bs->total_sectors = ret;
+    return 0;
+}
+
+static int nfs_file_create(const char *url, QEMUOptionParameter *options,
+                           Error **errp)
+{
+    int ret = 0;
+    int64_t total_size = 0;
+    NFSClient *client = g_malloc0(sizeof(NFSClient));
+
+    /* Read out options */
+    while (options && options->name) {
+        if (!strcmp(options->name, "size")) {
+            total_size = options->value.n;
+        }
+        options++;
+    }
+
+    ret = nfs_client_open(client, url, O_CREAT, errp);
+    if (ret < 0) {
+        goto out;
+    }
+    ret = nfs_ftruncate(client->context, client->fh, total_size);
+    nfs_client_close(client);
+out:
+    g_free(client);
+    return ret;
+}
+
+static int nfs_has_zero_init(BlockDriverState *bs)
+{
+    NFSClient *client = bs->opaque;
+    return client->has_zero_init;
+}
+
+static int64_t nfs_get_allocated_file_size(BlockDriverState *bs)
+{
+    NFSClient *client = bs->opaque;
+    NFSRPC task = {0};
+    struct stat st;
+
+    task.st = &st;
+    if (nfs_fstat_async(client->context, client->fh, nfs_co_generic_cb,
+                        &task) != 0) {
+        return -ENOMEM;
+    }
+
+    while (!task.complete) {
+        nfs_set_events(client);
+        qemu_aio_wait();
+    }
+
+    return (task.ret < 0 ? task.ret : st.st_blocks * st.st_blksize);
+}
+
+static int nfs_file_truncate(BlockDriverState *bs, int64_t offset)
+{
+    NFSClient *client = bs->opaque;
+    return nfs_ftruncate(client->context, client->fh, offset);
+}
+
+static BlockDriver bdrv_nfs = {
+    .format_name     = "nfs",
+    .protocol_name   = "nfs",
+
+    .instance_size   = sizeof(NFSClient),
+    .bdrv_needs_filename = true,
+    .bdrv_has_zero_init = nfs_has_zero_init,
+    .bdrv_get_allocated_file_size = nfs_get_allocated_file_size,
+    .bdrv_truncate = nfs_file_truncate,
+
+    .bdrv_file_open  = nfs_file_open,
+    .bdrv_close      = nfs_file_close,
+    .bdrv_create     = nfs_file_create,
+
+    .bdrv_co_readv         = nfs_co_readv,
+    .bdrv_co_writev        = nfs_co_writev,
+    .bdrv_co_flush_to_disk = nfs_co_flush,
+};
+
+static void nfs_block_init(void)
+{
+    bdrv_register(&bdrv_nfs);
+}
+
+block_init(nfs_block_init);