Re: [Qemu-devel] [PATCH v7 5/5] block: Support GlusterFS as a QEMU block backend.

[Kevin Wolf]

Am 17.09.2012 17:26, schrieb Bharata B Rao:
> block: Support GlusterFS as a QEMU block backend.
> 
> From: Bharata B Rao <address@hidden>
> 
> This patch adds gluster as the new block backend in QEMU. This gives
> QEMU the ability to boot VM images from gluster volumes. Its already
> possible to boot from VM images on gluster volumes using FUSE mount, but
> this patchset provides the ability to boot VM images from gluster volumes
> by by-passing the FUSE layer in gluster. This is made possible by
> using libgfapi routines to perform IO on gluster volumes directly.
> 
> VM Image on gluster volume is specified like this:
> 
> file=gluster[+transport]://[server[:port]]/volname/image[?socket=...]
> 
> 'gluster' is the protocol.
> 
> 'transport' specifies the transport type used to connect to gluster
> management daemon (glusterd). Valid transport types are
> tcp, unix and rdma. If the transport type isn't specified, then tcp
> type is assumed.
> 
> 'server' specifies the server where the volume file specification for
> the given volume resides. This can be either hostname or ipv4 address
> or ipv6 address. ipv6 address needs to be with in square brackets [ ].
> If transport type is 'unix', then server field is ignored, but 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. port is ignored for unix type of transport.
> 
> 'volname' is the name of the gluster volume which contains the VM image.
> 
> 'image' 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://[1:2:3:4:5:6:7:8]/testvol/dir/a.img
> file=gluster+tcp://[1:2:3:4:5:6:7:8]:24007/testvol/dir/a.img
> file=gluster+tcp://server.domain.com:24007/testvol/dir/a.img
> file=gluster+unix:///testvol/dir/a.img?socket=/tmp/glusterd.socket
> file=gluster+rdma://1.2.3.4:24007/testvol/a.img
> 
> Signed-off-by: Bharata B Rao <address@hidden>
> ---
> 
>  block/Makefile.objs |    1 
>  block/gluster.c     |  694 
> +++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 695 insertions(+), 0 deletions(-)
>  create mode 100644 block/gluster.c
> 
> 
> diff --git a/block/Makefile.objs b/block/Makefile.objs
> index b5754d3..a1ae67f 100644
> --- a/block/Makefile.objs
> +++ b/block/Makefile.objs
> @@ -9,3 +9,4 @@ block-obj-$(CONFIG_POSIX) += raw-posix.o
>  block-obj-$(CONFIG_LIBISCSI) += iscsi.o
>  block-obj-$(CONFIG_CURL) += curl.o
>  block-obj-$(CONFIG_RBD) += rbd.o
> +block-obj-$(CONFIG_GLUSTERFS) += gluster.o
> diff --git a/block/gluster.c b/block/gluster.c
> new file mode 100644
> index 0000000..0de3286
> --- /dev/null
> +++ b/block/gluster.c
> @@ -0,0 +1,694 @@
> +/*
> + * GlusterFS backend for QEMU
> + *
> + * Copyright (C) 2012 Bharata B Rao <address@hidden>
> + *
> + * Pipe handling mechanism in AIO implementation is derived from
> + * block/rbd.c. Hence,
> + *
> + * Copyright (C) 2010-2011 Christian Brunner <address@hidden>,
> + *                         Josh Durgin <address@hidden>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.  See
> + * the COPYING file in the top-level directory.
> + *
> + * Contributions after 2012-01-13 are licensed under the terms of the
> + * GNU GPL, version 2 or (at your option) any later version.
> + */
> +#include <glusterfs/api/glfs.h>
> +#include "block_int.h"
> +#include "qemu_socket.h"
> +
> +typedef struct GlusterAIOCB {
> +    BlockDriverAIOCB common;
> +    int64_t size;
> +    int ret;
> +    bool *finished;
> +    QEMUBH *bh;
> +} GlusterAIOCB;
> +
> +typedef struct BDRVGlusterState {
> +    struct glfs *glfs;
> +    int fds[2];
> +    struct glfs_fd *fd;
> +    int qemu_aio_count;
> +    int event_reader_pos;
> +    GlusterAIOCB *event_acb;
> +} BDRVGlusterState;
> +
> +#define GLUSTER_FD_READ 0
> +#define GLUSTER_FD_WRITE 1
> +
> +#define GLUSTER_TRANSPORT_DEFAULT        "gluster://"
> +#define GLUSTER_TRANSPORT_DEFAULT_SZ     strlen(GLUSTER_TRANSPORT_DEFAULT)
> +#define GLUSTER_TRANSPORT_TCP            "gluster+tcp://"
> +#define GLUSTER_TRANSPORT_TCP_SZ         strlen(GLUSTER_TRANSPORT_TCP)
> +#define GLUSTER_TRANSPORT_UNIX           "gluster+unix://"
> +#define GLUSTER_TRANSPORT_UNIX_SZ        strlen(GLUSTER_TRANSPORT_UNIX)
> +#define GLUSTER_TRANSPORT_RDMA           "gluster+rdma://"
> +#define GLUSTER_TRANSPORT_RDMA_SZ        strlen(GLUSTER_TRANSPORT_RDMA)
> +
> +typedef struct GlusterURI {
> +    char *server;
> +    int port;
> +    char *volname;
> +    char *image;
> +    char *transport;
> +    bool is_unix;
> +} GlusterURI;
> +
> +static void qemu_gluster_uri_free(GlusterURI *uri)
> +{
> +    g_free(uri->server);
> +    g_free(uri->volname);
> +    g_free(uri->image);
> +    g_free(uri->transport);
> +    g_free(uri);
> +}
> +
> +static int parse_socket(GlusterURI *uri, char *socket)
> +{
> +    char *token, *saveptr;
> +
> +    if (!socket) {
> +        return 0;
> +    }
> +    token = strtok_r(socket, "=", &saveptr);
> +    if (!token || strcmp(token, "socket")) {
> +        return -EINVAL;
> +    }
> +    token = strtok_r(NULL, "=", &saveptr);
> +    if (!token) {
> +        return -EINVAL;
> +    }
> +    uri->server = g_strdup(token);
> +    uri->is_unix = true;
> +    return 0;
> +}
> +
> +static int parse_gluster_spec(GlusterURI *uri, char *spec)
> +{
> +    char *token, *saveptr;
> +    int ret;
> +    QemuOpts *opts;
> +    char *p, *q;
> +
> +    /* transport */
> +    p = spec;
> +    if (!strncmp(p, GLUSTER_TRANSPORT_DEFAULT, 
> GLUSTER_TRANSPORT_DEFAULT_SZ)) {
> +        uri->transport = g_strdup("tcp");
> +        p += GLUSTER_TRANSPORT_DEFAULT_SZ;
> +    } else if (!strncmp(p, GLUSTER_TRANSPORT_TCP, GLUSTER_TRANSPORT_TCP_SZ)) 
> {
> +        uri->transport = g_strdup("tcp");
> +        p += GLUSTER_TRANSPORT_TCP_SZ;
> +    } else if (!strncmp(p, GLUSTER_TRANSPORT_UNIX, 
> GLUSTER_TRANSPORT_UNIX_SZ)) {
> +        uri->transport = g_strdup("unix");
> +        p += GLUSTER_TRANSPORT_UNIX_SZ;
> +    } else if (!strncmp(p, GLUSTER_TRANSPORT_RDMA, 
> GLUSTER_TRANSPORT_RDMA_SZ)) {

Would look a bit nicer with strstart() form cutils.c instead of strncmp().

> +        uri->transport = g_strdup("rdma");
> +        p += GLUSTER_TRANSPORT_RDMA_SZ;
> +    } else {
> +        return -EINVAL;
> +    }
> +    q = p;
> +
> +    /* server */
> +    if (!strcmp(uri->transport, "unix")) {
> +        if (!uri->is_unix) {
> +            return -EINVAL;
> +        }
> +    } else {
> +        if (uri->is_unix) {
> +            return -EINVAL;
> +        }
> +        p = strchr(p, '/');
> +        if (!p) {
> +            return -EINVAL;
> +        }
> +        *p++ = '\0';
> +        opts = qemu_opts_create(qemu_find_opts("inet"), NULL, 0, NULL);
> +        ret = inet_parse(opts, q);
> +        if (!ret) {
> +            uri->server = g_strdup(qemu_opt_get(opts, "host"));
> +            uri->port = strtoul(qemu_opt_get(opts, "port"), NULL, 0);
> +            if (uri->port < 0) {
> +                ret = -EINVAL;
> +            }
> +        }
> +        qemu_opts_del(opts);
> +        if (ret < 0) {
> +            return -EINVAL;
> +        }
> +    }
> +
> +    /* volname */
> +    token = strtok_r(p, "/", &saveptr);
> +    if (!token) {
> +        return -EINVAL;
> +    }
> +    uri->volname = g_strdup(token);
> +
> +    /* image */
> +    token = strtok_r(NULL, "?", &saveptr);
> +    if (!token) {
> +        return -EINVAL;
> +    }
> +    uri->image = g_strdup(token);
> +    return 0;
> +}
> +
> +/*
> + * file=gluster[+transport]://[server[:port]]/volname/image[?socket=...]
> + *
> + * 'gluster' is the protocol.
> + *
> + * 'transport' specifies the transport type used to connect to gluster
> + * management daemon (glusterd). Valid transport types are
> + * tcp, unix and rdma. If the transport type isn't specified, then tcp
> + * type is assumed.
> + *
> + * 'server' specifies the server where the volume file specification for
> + * the given volume resides. This can be either hostname or ipv4 address
> + * or ipv6 address. ipv6 address needs to be with in square brackets [ ].
> + * If transport type is 'unix', then server field is ignored, but 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. port is ignored for unix type of transport.
> + *
> + * 'volname' is the name of the gluster volume which contains the VM image.
> + *
> + * 'image' 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://[1:2:3:4:5:6:7:8]/testvol/dir/a.img
> + * file=gluster+tcp://[1:2:3:4:5:6:7:8]:24007/testvol/dir/a.img
> + * file=gluster+tcp://server.domain.com:24007/testvol/dir/a.img
> + * file=gluster+unix:///testvol/dir/a.img?socket=/tmp/glusterd.socket
> + * file=gluster+rdma://1.2.3.4:24007/testvol/a.img
> + */
> +static int qemu_gluster_parseuri(GlusterURI *uri, const char *filename)
> +{
> +    char *token, *saveptr;
> +    char *p, *q, *gluster_spec = NULL;
> +    int ret = -EINVAL;
> +
> +    p = q = g_strdup(filename);

Neither p nor q are changed, so one variable would be enough.

> +
> +    /* Extract server, volname and image */
> +    token = strtok_r(p, "?", &saveptr);
> +    if (!token) {
> +        goto out;
> +    }
> +    gluster_spec = g_strdup(token);
> +
> +    /* socket */
> +    token = strtok_r(NULL, "?", &saveptr);
> +    ret = parse_socket(uri, token);
> +    if (ret < 0) {
> +        goto out;
> +     }

The is_unix thing feels a bit backwards. You set it whenever an option
is present, and fail if a protocol other than gluster+unix:// is used.

Wouldn't it make more sense to set it depending on the protocol and then
check in the option parser if is_unix == true when there is a 'socket'
option? Otherwise adding non-unix options later is going to become hard.

The rest looks good now.

Kevin