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Re: [Qemu-devel] [PATCHv7 1/5] block: add native support for NFS


From: Stefan Hajnoczi
Subject: Re: [Qemu-devel] [PATCHv7 1/5] block: add native support for NFS
Date: Thu, 30 Jan 2014 10:05:55 +0100
User-agent: Mutt/1.5.21 (2010-09-15)

On Wed, Jan 29, 2014 at 05:38:29PM +0100, Peter Lieven wrote:
> On 29.01.2014 17:19, Benoît Canet wrote:
> >Le Wednesday 29 Jan 2014 à 09:50:21 (+0100), Peter Lieven a écrit :
> >>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 <address@hidden>
> >>---
> >>  MAINTAINERS         |    5 +
> >>  block/Makefile.objs |    1 +
> >>  block/nfs.c         |  440 
> >> +++++++++++++++++++++++++++++++++++++++++++++++++++
> >>  configure           |   26 +++
> >>  qapi-schema.json    |    1 +
> >>  5 files changed, 473 insertions(+)
> >>  create mode 100644 block/nfs.c
> >>
> >>diff --git a/MAINTAINERS b/MAINTAINERS
> >>index fb53242..f8411f9 100644
> >>--- a/MAINTAINERS
> >>+++ b/MAINTAINERS
> >>@@ -936,6 +936,11 @@ M: Peter Lieven <address@hidden>
> >>  S: Supported
> >>  F: block/iscsi.c
> >>+NFS
> >>+M: Peter Lieven <address@hidden>
> >>+S: Maintained
> >>+F: block/nfs.c
> >>+
> >>  SSH
> >>  M: Richard W.M. Jones <address@hidden>
> >>  S: Supported
> >>diff --git a/block/Makefile.objs b/block/Makefile.objs
> >>index 4e8c91e..e254a21 100644
> >>--- a/block/Makefile.objs
> >>+++ b/block/Makefile.objs
> >>@@ -12,6 +12,7 @@ block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
> >>  ifeq ($(CONFIG_POSIX),y)
> >>  block-obj-y += nbd.o nbd-client.o sheepdog.o
> >>  block-obj-$(CONFIG_LIBISCSI) += iscsi.o
> >>+block-obj-$(CONFIG_LIBNFS) += nfs.o
> >>  block-obj-$(CONFIG_CURL) += curl.o
> >>  block-obj-$(CONFIG_RBD) += rbd.o
> >>  block-obj-$(CONFIG_GLUSTERFS) += gluster.o
> >>diff --git a/block/nfs.c b/block/nfs.c
> >>new file mode 100644
> >>index 0000000..2bbf7a2
> >>--- /dev/null
> >>+++ b/block/nfs.c
> >>@@ -0,0 +1,440 @@
> >>+/*
> >>+ * QEMU Block driver for native access to files on NFS shares
> >>+ *
> >>+ * Copyright (c) 2014 Peter Lieven <address@hidden>
> >>+ *
> >>+ * 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 status;
> >>+    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 status, struct nfs_context *nfs, void *data,
> >>+                  void *private_data)
> >>+{
> >>+    NFSRPC *task = private_data;
> >>+    task->complete = 1;
> >>+    task->status = status;
> >>+    if (task->status > 0 && task->iov) {
> >>+        if (task->status <= task->iov->size) {
> >It feel very odd to compare something named status with something named size.
> >
> >>+            qemu_iovec_from_buf(task->iov, 0, data, task->status);
> >>+        } else {
> >>+            task->status = -EIO;
> >>+        }
> >>+    }
> >>+    if (task->status == 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.status < 0) {
> >>+        return task.status;
> >>+    }
> >>+
> >>+    /* zero pad short reads */
> >>+    if (task.status < iov->size) {
> >>+        qemu_iovec_memset(iov, task.status, 0, iov->size - task.status);
> >>+    }
> >>+
> >>+    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.status != nb_sectors * BDRV_SECTOR_SIZE) {
> >>+        return task.status < 0 ? task.status : -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.status;
> >>+}
> >>+
> >>+/* 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_.cilclient_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;
> >Should this be goto out since we don't have done nfs_init_context yet ?
> >>+    }
> >>+    strp = strrchr(uri->path, '/');
> >>+    if (strp == NULL) {
> >>+        error_setg(errp, "Invalid URL specified");
> >>+        goto fail;
> >goto out ?
> >>+    }
> >>+    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)) {
> >>+        qerror_report_err(local_err);
> >I have seen more usage of error_propagate(errp, local_err); in QEMU code.
> >Maybe I am missing the point.
> >
> >>+        error_free(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);
> >>+out:
> >Should the out: label be after nfs_client_close(client); since the code will
> >jump to it on nfs_client_open failure ?
> You are right, but it doesn't hurt since you can call nfs_client_close 
> multiple
> times.

Will you send another revision addressing the other comments?

Stefan



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