GlusterFS supports creation of zero-filled file on GlusterFS volume by means of an API called glfs_zerofill(). Use this API from QEMU to create an image that is filled with zeroes by using the preallocation option of qemu-img.
qemu-img create gluster://server/volume/image -o preallocation=full 10G The allowed values for preallocation are 'full' and 'off'. By default preallocation is off and image is not zero-filled. glfs_zerofill() offloads the writing of zeroes to the server and if the storage supports SCSI WRITESAME, GlusterFS server can issue BLKZEROOUT ioctl to achieve the zeroing. Signed-off-by: Bharata B Rao <bhar...@linux.vnet.ibm.com> --- block/gluster.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 49 insertions(+), 1 deletion(-) diff --git a/block/gluster.c b/block/gluster.c index 1390270..c167abe 100644 --- a/block/gluster.c +++ b/block/gluster.c @@ -364,6 +364,29 @@ out: qemu_aio_release(acb); return ret; } + +static inline int gluster_supports_zerofill(void) +{ + return 1; +} + +static inline int qemu_gluster_zerofill(struct glfs_fd *fd, int64_t offset, + int64_t size) +{ + return glfs_zerofill(fd, offset, size); +} + +#else +static inline int gluster_supports_zerofill(void) +{ + return 0; +} + +static inline int qemu_gluster_zerofill(struct glfs_fd *fd, int64_t offset, + int64_t size) +{ + return 0; +} #endif static int qemu_gluster_create(const char *filename, @@ -372,6 +395,7 @@ static int qemu_gluster_create(const char *filename, struct glfs *glfs; struct glfs_fd *fd; int ret = 0; + int prealloc = 0; int64_t total_size = 0; GlusterConf *gconf = g_malloc0(sizeof(GlusterConf)); @@ -384,6 +408,19 @@ static int qemu_gluster_create(const char *filename, while (options && options->name) { if (!strcmp(options->name, BLOCK_OPT_SIZE)) { total_size = options->value.n / BDRV_SECTOR_SIZE; + } else if (!strcmp(options->name, BLOCK_OPT_PREALLOC)) { + if (!options->value.s || !strcmp(options->value.s, "off")) { + prealloc = 0; + } else if (!strcmp(options->value.s, "full") && + gluster_supports_zerofill()) { + prealloc = 1; + } else { + error_setg(errp, "Invalid preallocation mode: '%s'" + " or GlusterFS doesn't support zerofill API", + options->value.s); + ret = -EINVAL; + goto out; + } } options++; } @@ -393,9 +430,15 @@ static int qemu_gluster_create(const char *filename, if (!fd) { ret = -errno; } else { - if (glfs_ftruncate(fd, total_size * BDRV_SECTOR_SIZE) != 0) { + if (!glfs_ftruncate(fd, total_size * BDRV_SECTOR_SIZE)) { + if (prealloc && qemu_gluster_zerofill(fd, 0, + total_size * BDRV_SECTOR_SIZE)) { + ret = -errno; + } + } else { ret = -errno; } + if (glfs_close(fd) != 0) { ret = -errno; } @@ -579,6 +622,11 @@ static QEMUOptionParameter qemu_gluster_create_options[] = { .type = OPT_SIZE, .help = "Virtual disk size" }, + { + .name = BLOCK_OPT_PREALLOC, + .type = OPT_STRING, + .help = "Preallocation mode (allowed values: off, full)" + }, { NULL } }; -- 1.7.11.7