[Qemu-devel] [RFC PATCH 2/2] block: gluster as block backend

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

block: gluster as block backend

From: Bharata B Rao <bharata@linux.vnet.ibm.com>

This patch adds gluster as the new block backend in QEMU. This gives QEMU
the ability to boot VM images from gluster volumes.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
---

 block/Makefile.objs |    1 
 block/gluster.c     |  483 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 484 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..c33a006
--- /dev/null
+++ b/block/gluster.c
@@ -0,0 +1,483 @@
+/*
+ * GlusterFS backend for QEMU
+ *
+ * (AIO implementation is derived from block/rbd.c)
+ *
+ * Copyright (C) 2012 Bharata B Rao <bharata@linux.vnet.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * (at your option) any later version. See the COPYING file in the top-level
+ * directory.
+ */
+#include "block_int.h"
+#include <glusterfs/api/glfs.h>
+
+typedef struct GlusterConf {
+    char server[HOST_NAME_MAX];
+    int port;
+    char volname[128]; /* TODO: use GLUSTERD_MAX_VOLUME_NAME */
+    char image[PATH_MAX];
+} GlusterConf;
+
+typedef struct GlusterAIOCB {
+    BlockDriverAIOCB common;
+    QEMUIOVector *qiov;
+    char *bounce;
+    struct BDRVGlusterState *s;
+    int cancelled;
+} GlusterAIOCB;
+
+typedef struct GlusterCBKData {
+    GlusterAIOCB *acb;
+    struct BDRVGlusterState *s;
+    int64_t size;
+    int ret;
+} GlusterCBKData;
+
+typedef struct BDRVGlusterState {
+    struct glfs *glfs;
+    int fds[2];
+    int open_flags;
+    struct glfs_fd *fd;
+    int qemu_aio_count;
+    int event_reader_pos;
+    GlusterCBKData *event_gcbk;
+} BDRVGlusterState;
+
+#define GLUSTER_FD_READ 0
+#define GLUSTER_FD_WRITE 1
+
+static void qemu_gluster_complete_aio(GlusterCBKData *gcbk)
+{
+    GlusterAIOCB *acb = gcbk->acb;
+    int ret;
+
+    if (acb->cancelled) {
+        qemu_aio_release(acb);
+        goto done;
+    }
+
+    if (gcbk->ret == gcbk->size) {
+        ret = 0; /* Success */
+    } else if (gcbk->ret < 0) {
+        ret = gcbk->ret; /* Read/Write failed */
+    } else {
+        ret = -EINVAL; /* Partial read/write - fail it */
+    }
+    acb->common.cb(acb->common.opaque, ret);
+    qemu_aio_release(acb);
+
+done:
+    g_free(gcbk);
+}
+
+static void qemu_gluster_aio_event_reader(void *opaque)
+{
+    BDRVGlusterState *s = opaque;
+    ssize_t ret;
+
+    do {
+        char *p = (char *)&s->event_gcbk;
+
+        ret = read(s->fds[GLUSTER_FD_READ], p + s->event_reader_pos,
+                   sizeof(s->event_gcbk) - s->event_reader_pos);
+        if (ret > 0) {
+            s->event_reader_pos += ret;
+            if (s->event_reader_pos == sizeof(s->event_gcbk)) {
+                s->event_reader_pos = 0;
+                qemu_gluster_complete_aio(s->event_gcbk);
+                s->qemu_aio_count--;
+            }
+        }
+    } while (ret < 0 && errno == EINTR);
+}
+
+static int qemu_gluster_aio_flush_cb(void *opaque)
+{
+    BDRVGlusterState *s = opaque;
+
+    return (s->qemu_aio_count > 0);
+}
+
+/*
+ * file=protocol:server@port:volname:image
+ */
+static int qemu_gluster_parsename(GlusterConf *c, const char *filename)
+{
+    char *file = g_strdup(filename);
+    char *token, *next_token, *saveptr;
+    char *token_s, *next_token_s, *saveptr_s;
+    int ret = -EINVAL;
+
+    /* Discard the protocol */
+    token = strtok_r(file, ":", &saveptr);
+    if (!token) {
+        goto out;
+    }
+
+    /* server@port */
+    next_token = strtok_r(NULL, ":", &saveptr);
+    if (!next_token) {
+        goto out;
+    }
+    if (strchr(next_token, '@')) {
+        token_s = strtok_r(next_token, "@", &saveptr_s);
+        if (!token_s) {
+            goto out;
+        }
+        strncpy(c->server, token_s, HOST_NAME_MAX);
+        next_token_s = strtok_r(NULL, "@", &saveptr_s);
+        if (!next_token_s) {
+            goto out;
+        }
+        c->port = atoi(next_token_s);
+    } else {
+        strncpy(c->server, next_token, HOST_NAME_MAX);
+        c->port = 0;
+    }
+
+    /* volname */
+    next_token = strtok_r(NULL, ":", &saveptr);
+    if (!next_token) {
+        goto out;
+    }
+    strncpy(c->volname, next_token, 128);
+
+    /* image */
+    next_token = strtok_r(NULL, ":", &saveptr);
+    if (!next_token) {
+        goto out;
+    }
+    strncpy(c->image, next_token, PATH_MAX);
+    ret = 0;
+out:
+    g_free(file);
+    return ret;
+}
+
+static struct glfs *qemu_gluster_init(GlusterConf *c, const char *filename)
+{
+    struct glfs *glfs = NULL;
+    int ret;
+
+    ret = qemu_gluster_parsename(c, filename);
+    if (ret < 0) {
+        errno = -ret;
+        goto out;
+    }
+
+    glfs = glfs_new(c->volname);
+    if (!glfs) {
+        goto out;
+    }
+
+    ret = glfs_set_volfile_server(glfs, "socket", c->server, c->port);
+    if (ret < 0) {
+        goto out;
+    }
+
+    /*
+     * TODO: Logging is not necessary but instead nice to have.
+     * Can QEMU optionally log into a standard place ?
+     * Need to use defines like gf_loglevel_t:GF_LOG_INFO instead of
+     * hard coded values like 7 here.
+     */
+    ret = glfs_set_logging(glfs, "/tmp/qemu-gluster.log", 7);
+    if (ret < 0) {
+        goto out;
+    }
+
+    ret = glfs_init(glfs);
+    if (ret < 0) {
+        goto out;
+    }
+    return glfs;
+
+out:
+    if (glfs) {
+        (void)glfs_fini(glfs);
+    }
+    return NULL;
+}
+
+static int qemu_gluster_open(BlockDriverState *bs, const char *filename,
+    int bdrv_flags)
+{
+    BDRVGlusterState *s = bs->opaque;
+    GlusterConf *c = g_malloc(sizeof(GlusterConf));
+    int ret;
+
+    s->glfs = qemu_gluster_init(c, filename);
+    if (!s->glfs) {
+        ret = -errno;
+        goto out;
+    }
+
+    s->open_flags |=  O_BINARY;
+    s->open_flags &= ~O_ACCMODE;
+    if (bdrv_flags & BDRV_O_RDWR) {
+        s->open_flags |= O_RDWR;
+    } else {
+        s->open_flags |= O_RDONLY;
+    }
+
+    if ((bdrv_flags & BDRV_O_NOCACHE)) {
+        s->open_flags |= O_DIRECT;
+    }
+
+    s->fd = glfs_open(s->glfs, c->image, s->open_flags);
+    if (!s->fd) {
+        ret = -errno;
+        goto out;
+    }
+
+    ret = qemu_pipe(s->fds);
+    if (ret < 0) {
+        goto out;
+    }
+    fcntl(s->fds[0], F_SETFL, O_NONBLOCK);
+    fcntl(s->fds[1], F_SETFL, O_NONBLOCK);
+    qemu_aio_set_fd_handler(s->fds[GLUSTER_FD_READ],
+        qemu_gluster_aio_event_reader, NULL, qemu_gluster_aio_flush_cb, s);
+    g_free(c);
+    return ret;
+
+out:
+    g_free(c);
+    if (s->fd) {
+        glfs_close(s->fd);
+    }
+    if (s->glfs) {
+        (void) glfs_fini(s->glfs);
+    }
+    return ret;
+}
+
+static int qemu_gluster_create(const char *filename,
+        QEMUOptionParameter *options)
+{
+    struct glfs *glfs;
+    struct glfs_fd *fd;
+    GlusterConf *c = g_malloc(sizeof(GlusterConf));
+    int ret = 0;
+    int64_t total_size = 0;
+
+    glfs = qemu_gluster_init(c, filename);
+    if (!glfs) {
+        ret = -errno;
+        goto out;
+    }
+
+    /* Read out options */
+    while (options && options->name) {
+        if (!strcmp(options->name, BLOCK_OPT_SIZE)) {
+            total_size = options->value.n / BDRV_SECTOR_SIZE;
+        }
+        options++;
+    }
+
+    fd = glfs_creat(glfs, c->image, O_WRONLY|O_CREAT|O_TRUNC|O_BINARY, S_IRWXU);
+    if (!fd) {
+        ret = -errno;
+    } else {
+        if (glfs_ftruncate(fd, total_size * BDRV_SECTOR_SIZE) != 0) {
+            ret = -errno;
+        }
+        if (glfs_close(fd) != 0) {
+            ret = -errno;
+        }
+    }
+out:
+    g_free(c);
+    if (glfs) {
+        (void) glfs_fini(glfs);
+    }
+    return ret;
+}
+
+static AIOPool gluster_aio_pool = {
+    .aiocb_size = sizeof(GlusterAIOCB),
+};
+
+static int qemu_gluster_send_pipe(BDRVGlusterState *s, GlusterCBKData *gcbk)
+{
+    int ret = 0;
+    while (1) {
+        fd_set wfd;
+        int fd = s->fds[GLUSTER_FD_WRITE];
+
+        ret = write(fd, (void *)&gcbk, sizeof(gcbk));
+        if (ret >= 0) {
+            break;
+        }
+        if (errno == EINTR) {
+            continue;
+        }
+        if (errno != EAGAIN) {
+            break;
+        }
+
+        FD_ZERO(&wfd);
+        FD_SET(fd, &wfd);
+        do {
+            ret = select(fd + 1, NULL, &wfd, NULL, NULL);
+        } while (ret < 0 && errno == EINTR);
+    }
+    return ret;
+}
+
+static void gluster_finish_aiocb(struct glfs_fd *fd, ssize_t ret, void *arg)
+{
+    GlusterCBKData *gcbk = (GlusterCBKData *)arg;
+    BDRVGlusterState *s = gcbk->s;
+
+    gcbk->ret = ret;
+    if (qemu_gluster_send_pipe(s, gcbk) < 0) {
+        error_report("Could not complete read/write/flush from gluster");
+        abort();
+    }
+}
+
+static BlockDriverAIOCB *qemu_gluster_aio_rw(BlockDriverState *bs,
+        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
+        BlockDriverCompletionFunc *cb, void *opaque, int write)
+{
+    int ret;
+    GlusterAIOCB *acb;
+    GlusterCBKData *gcbk;
+    BDRVGlusterState *s = bs->opaque;
+    size_t size;
+    off_t offset;
+
+    acb = qemu_aio_get(&gluster_aio_pool, bs, cb, opaque);
+    acb->qiov = qiov;
+    acb->s = s;
+
+    offset = sector_num * BDRV_SECTOR_SIZE;
+    size = nb_sectors * BDRV_SECTOR_SIZE;
+    s->qemu_aio_count++;
+
+    gcbk = g_malloc(sizeof(GlusterCBKData));
+    gcbk->acb = acb;
+    gcbk->s = s;
+    gcbk->size = size;
+
+    if (write) {
+        ret = glfs_pwritev_async(s->fd, qiov->iov, qiov->niov, offset, 0,
+            &gluster_finish_aiocb, gcbk);
+    } else {
+        ret = glfs_preadv_async(s->fd, qiov->iov, qiov->niov, offset, 0,
+            &gluster_finish_aiocb, gcbk);
+    }
+
+    if (ret < 0) {
+        goto out;
+    }
+    return &acb->common;
+
+out:
+    g_free(gcbk);
+    s->qemu_aio_count--;
+    qemu_aio_release(acb);
+    return NULL;
+}
+
+static BlockDriverAIOCB *qemu_gluster_aio_readv(BlockDriverState *bs,
+        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
+        BlockDriverCompletionFunc *cb, void *opaque)
+{
+    return qemu_gluster_aio_rw(bs, sector_num, qiov, nb_sectors, cb, opaque, 0);
+}
+
+static BlockDriverAIOCB *qemu_gluster_aio_writev(BlockDriverState *bs,
+        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
+        BlockDriverCompletionFunc *cb, void *opaque)
+{
+    return qemu_gluster_aio_rw(bs, sector_num, qiov, nb_sectors, cb, opaque, 1);
+}
+
+static BlockDriverAIOCB *qemu_gluster_aio_flush(BlockDriverState *bs,
+        BlockDriverCompletionFunc *cb, void *opaque)
+{
+    int ret;
+    GlusterAIOCB *acb;
+    GlusterCBKData *gcbk;
+    BDRVGlusterState *s = bs->opaque;
+
+    acb = qemu_aio_get(&gluster_aio_pool, bs, cb, opaque);
+    acb->s = s;
+    s->qemu_aio_count++;
+
+    gcbk = g_malloc(sizeof(GlusterCBKData));
+    gcbk->acb = acb;
+    gcbk->s = s;
+    gcbk->size = 0;
+
+    ret = glfs_fsync_async(s->fd, &gluster_finish_aiocb, gcbk);
+    if (ret < 0) {
+        goto out;
+    }
+    return &acb->common;
+
+out:
+    g_free(gcbk);
+    s->qemu_aio_count--;
+    qemu_aio_release(acb);
+    return NULL;
+}
+
+static int64_t qemu_gluster_getlength(BlockDriverState *bs)
+{
+    BDRVGlusterState *s = bs->opaque;
+    struct stat st;
+    int ret;
+
+    ret = glfs_fstat(s->fd, &st);
+    if (ret < 0) {
+        return -errno;
+    } else {
+        return st.st_size;
+    }
+}
+
+static void qemu_gluster_close(BlockDriverState *bs)
+{
+    BDRVGlusterState *s = bs->opaque;
+
+    if (s->fd) {
+        glfs_close(s->fd);
+        s->fd = NULL;
+    }
+}
+
+static QEMUOptionParameter qemu_gluster_create_options[] = {
+    {
+        .name = BLOCK_OPT_SIZE,
+        .type = OPT_SIZE,
+        .help = "Virtual disk size"
+    },
+    { NULL }
+};
+
+static BlockDriver bdrv_gluster = {
+    .format_name = "gluster",
+    .protocol_name = "gluster",
+    .instance_size = sizeof(BDRVGlusterState),
+    .bdrv_file_open = qemu_gluster_open,
+    .bdrv_close = qemu_gluster_close,
+    .bdrv_create = qemu_gluster_create,
+    .bdrv_getlength = qemu_gluster_getlength,
+
+    .bdrv_aio_readv = qemu_gluster_aio_readv,
+    .bdrv_aio_writev = qemu_gluster_aio_writev,
+    .bdrv_aio_flush = qemu_gluster_aio_flush,
+
+    .create_options = qemu_gluster_create_options,
+};
+
+static void bdrv_gluster_init(void)
+{
+    bdrv_register(&bdrv_gluster);
+}
+
+block_init(bdrv_gluster_init);