Commit cf7f616b authored by Bharata B Rao's avatar Bharata B Rao Committed by Kevin Wolf
Browse files

gluster: Add support for creating zero-filled image 

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: default avatarBharata B Rao <bharata@linux.vnet.ibm.com>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 7c815372

block/gluster.c

+49 −1
Original line number Diff line number Diff line
@@ -354,6 +354,29 @@ out: 
    g_slice_free(GlusterAIOCB, acb);

    return ret;

}



static inline bool 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 bool 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,
@@ -362,6 +385,7 @@ 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));
@@ -374,6 +398,19 @@ 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++;

    }
@@ -383,9 +420,15 @@ 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;

        }
@@ -560,6 +603,11 @@ 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 }

};