Am 26.12.2013 um 13:48 hat Peter Lieven geschrieben:
> 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>
>
> 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
>
> LibNFS currently support NFS version 3 only.
>
> Signed-off-by: Peter Lieven <p...@kamp.de>
> ---
> v4->v5:
> - disussed with Ronnie and decided to move URL + Paramter parsing to LibNFS.
> This allows for URL parameter processing directly in LibNFS without
> altering
> the qemu NFS block driver. This bumps the version requirement for LibNFS
> to 1.9.0 though.
Considering that we'll likely want to add new options in the future, I'm
not sure if this is a good idea. This means that struct nfs_url will
change, and if qemu isn't updated, it might not even notice that some
option was requested in a new field that it doesn't know and provide,
so it will silently ignore it. Or if we have a qemu built against an
older libnfs, this must be marked as an incompatible ABI change, so it
can't run at all with the newer libnfs version.
> - added a pointer to the LibNFS readme where additional information about
> ROOT privilidge requirements can be found as this raised a few concerns.
> - removed a trailing dot in an error statement [Fam].
>
> v3->v4:
> - finally added full implementation of bdrv_get_allocated_file_size [Stefan]
> - removed trailing \n from error statements [Stefan]
>
> v2->v3:
> - rebased the stefanha/block
> - use pkg_config to check for libnfs (ignoring cflags which are broken in
> 1.8.0) [Stefan]
> - fixed NFSClient declaration [Stefan]
> - renamed Task variables to task [Stefan]
> - renamed NFSTask to NFSRPC [Ronnie]
> - do not update bs->total_sectors in nfs_co_writev [Stefan]
> - return -ENOMEM on all async call failures [Stefan,Ronnie]
> - fully implement ftruncate
> - use util/uri.c for URL parsing [Stefan]
> - reworked nfs_file_open_common to nfs_client_open which works on NFSClient
> [Stefan]
> - added a comment ot the connect message that libnfs support NFSv3 only at
> the moment.
> - DID NOT add full implementation of bdrv_get_allocated_file_size because
> we are not in a coroutine context and I cannot do an async call here.
> I could do a sync call if there would be a guarantee that no requests
> are in flight. [Stefan]
>
> v1->v2:
> - fixed block/Makefile.objs [Ronnie]
> - do not always register a read handler [Ronnie]
> - add support for reading beyond EOF [Fam]
> - fixed struct and paramter naming [Fam]
> - fixed overlong lines and whitespace errors [Fam]
> - return return status from libnfs whereever possible [Fam]
> - added comment why we set allocated_file_size to -ENOTSUP after write [Fam]
> - avoid segfault when parsing filname [Fam]
> - remove unused close_bh from NFSClient [Fam]
> - avoid dividing and mutliplying total_size by BDRV_SECTOR_SIZE in
> nfs_file_create [Fam]
>
> MAINTAINERS | 5 +
> block/Makefile.objs | 1 +
> block/nfs.c | 405
> +++++++++++++++++++++++++++++++++++++++++++++++++++
> configure | 26 ++++
qapi-schema.json is missing, so you can't add NFS block devices using
blockdev-add.
> 4 files changed, 437 insertions(+)
> create mode 100644 block/nfs.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index a5ab8f8..09996ab 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -935,6 +935,11 @@ M: Peter Lieven <p...@kamp.de>
> S: Supported
> F: block/iscsi.c
>
> +NFS
> +M: Peter Lieven <p...@kamp.de>
> +S: Maintained
> +F: block/nfs.c
> +
> SSH
> M: Richard W.M. Jones <rjo...@redhat.com>
> 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..4023b71
> --- /dev/null
> +++ b/block/nfs.c
> @@ -0,0 +1,405 @@
> +/*
> + * QEMU Block driver for native access to files on NFS shares
> + *
> + * Copyright (c) 2013 Peter Lieven <p...@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 "sysemu/sysemu.h"
> +
> +#include <nfsc/libnfs-zdr.h>
> +#include <nfsc/libnfs.h>
> +#include <nfsc/libnfs-raw.h>
> +#include <nfsc/libnfs-raw-mount.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) {
> + qemu_iovec_from_buf(task->iov, 0, data, task->status);
> + } else {
> + task->status = -EIO;
Short reads don't happen in practice with libnfs?
> + }
> + }
> + 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;
> + }
> +
> + 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;
Does this duplicate the logic of nfs_co_generic_cb?
> + }
> +
> + 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;
> +}
> +
> +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 */ }
> + },
> +};
I think this is the point where I disagree. First of all, if it's a URL,
call it "url" instead of "filename". But more importantly, a URL encodes
options in a string instead of structured options that can be set
separately.
I would split this into options 'server', 'path', etc. and only have
bdrv_parse_filename() invoke the URL parsing to fill these options if
the user preferred the URL style.
Kevin
