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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [xen-devel][PATCH 3/5] xl disk configuration parsing changes
On Mon, 7 Feb 2011, Kamala Narasimhan wrote:
> diff -u -r libxl-interface-changes/xl_cmdimpl.c libxl/xl_cmdimpl.c
> --- libxl-interface-changes/xl_cmdimpl.c 2011-02-07 12:03:37.000000000
> -0500
> +++ libxl/xl_cmdimpl.c 2011-02-07 14:58:39.000000000 -0500
> @@ -438,143 +438,184 @@
> return 0;
> }
>
> -#define DSTATE_INITIAL 0
> -#define DSTATE_TAP 1
> -#define DSTATE_PHYSPATH 2
> -#define DSTATE_VIRTPATH 3
> -#define DSTATE_VIRTTYPE 4
> -#define DSTATE_RW 5
> -#define DSTATE_TERMINAL 6
> +#define DSTATE_INITIAL 0
> +#define DSTATE_ATTRIB_PARSED 1
> +#define DSTATE_VDEV_PARSED 2
Why did you need to remove 4 states?
Also it would be nice to split this patch in two: a patch that
introduces parse_disk_attrib, parse_disk_vdev_info, etc, and a second
patch that makes any necessary changes to the state machine.
Otherwise it is very difficult to understand the reason behind each
change to the state machine.
> +static int parse_disk_attrib(libxl_device_disk *disk, char *attrib)
> +{
> + if ( attrib[0] == 'w' )
> + disk->readwrite = 1;
> + else if ( attrib[0] != 'r' ) {
> + LOG("Required access rights attribute is missing or incorrect in "
> + "disk configuration option %s", attrib);
> + return ERROR_INVAL;
> + }
> +
> + return 0;
> +}
> +
> +static int parse_disk_vdev_info(libxl_device_disk *disk, char *vdev_info)
> +{
> + char *vdev, *type;
> +
> + type = strchr(vdev_info, ':');
> + if ( type ) {
> + *type = '\0';
> + type++;
> + if ( !strncmp(type, "cdrom", sizeof("cdrom")-1) ) {
> + disk->is_cdrom = 1;
> + disk->unpluggable = 1;
> + }
> + else {
> + LOG("Invalid vdev type %s specified in disk configuration
> option",
> + type);
> + return ERROR_INVAL;
> + }
> + }
> +
> + vdev = vdev_info;
> + if ( vdev[0] == '\0' ) {
> + LOG("Mandatory attribute vdev not specified");
> + return ERROR_INVAL;
> + }
> +
> + disk->vdev = strdup(vdev);
> + return 0;
> +}
> +
> +static int parse_disk_pdev_info(libxl_device_disk *disk, char *pdev_info)
> +{
> + char *pdev_type, *pdev_impl, *pdev_format, *pdev_path;
> +
> + if ( pdev_info[0] == '\0' && !disk->is_cdrom ) {
> + /* pdev can be empty string only for cdrom drive with no media
> inserted */
> + LOG("Required vdev info missing in disk configuration option");
> + return ERROR_INVAL;
> + }
> +
> + pdev_path = strrchr(pdev_info, ':');
> + if ( !pdev_path ) {
> + disk->pdev_path = strdup(pdev_info);
> + return 0;
> + }
> +
> + *pdev_path = '\0';
> + disk->pdev_path = strdup(++pdev_path);
> +
> + pdev_format = strrchr(pdev_info, ':');
> + if ( !pdev_format )
> + pdev_format = pdev_info;
> + else {
> + *pdev_format = '\0';
> + pdev_format++;
> + }
> +
> + if ( !strncmp(pdev_format, "raw", sizeof("raw")-1) )
> + disk->format = DISK_FORMAT_RAW;
> + else if ( !strncmp(pdev_format, "qcow", sizeof("qcow")-1) )
> + disk->format = DISK_FORMAT_QCOW;
> + else if ( !strncmp(pdev_format, "qcow2", sizeof("qcow2")-1) )
> + disk->format = DISK_FORMAT_QCOW2;
> + else if ( !strncmp(pdev_format, "vhd", sizeof("vhd")-1) )
> + disk->format = DISK_FORMAT_VHD;
> +
> + if ( disk->format == DISK_FORMAT_UNKNOWN )
> + pdev_impl = pdev_format;
> + else {
> + pdev_impl = strrchr(pdev_info, ':');
> + if ( !pdev_impl )
> + return 0;
> + *pdev_impl = '\0';
> + pdev_impl++;
> + }
> +
> + if ( !strncmp(pdev_impl, "aio", sizeof("aio")-1) ||
> + !strncmp(pdev_impl, "tapdisk", sizeof("tapdisk")-1) )
> + disk->backend = DISK_BACKEND_TAPDISK2;
> + else if ( !strncmp(pdev_impl, "ioemu", sizeof("ioemu")-1) )
> + disk->backend = DISK_BACKEND_QEMU;
> +
> + if ( disk->backend == DISK_BACKEND_UNKNOWN )
> + pdev_type = pdev_impl;
> + else {
> + pdev_type = pdev_info;
> + if ( pdev_type[0] == '\0' )
> + return 0;
> + }
> +
> + if ( !strncmp(pdev_type, "phy", sizeof("phy")-1) )
> + disk->backend = DISK_BACKEND_BLKBACK;
> + else if ( !strncmp(pdev_type, "file", sizeof("file")-1) ||
> + !strncmp(pdev_type, "tap", sizeof("tap")-1) ||
> + !strncmp(pdev_type, "tap2", sizeof("tap2")-1) )
> + disk->backend = DISK_BACKEND_TAPDISK2;
> +
> + return 0;
> +}
> +
> +/*
> + * Note: Following code calls methods each of which will parse
> + * specific chunks of the disk configuration option, the specific
> + * chunks being attribute, vdev and pdev. As with any parsing code
> + * it makes assumption about the order in which specific chunks appear
> + * in the disk configuration option string. So, please use
> + * care while modifying the code below, esp. when it comes to
> + * the order of calls.
> + */
> static int parse_disk_config(libxl_device_disk *disk, char *buf2)
> {
> - int state = DSTATE_INITIAL;
> - char *p, *end, *tok;
> + int state = DSTATE_INITIAL, ret_val;
> + char *substr = buf2;
>
> memset(disk, 0, sizeof(*disk));
>
> - for(tok = p = buf2, end = buf2 + strlen(buf2) + 1; p < end; p++) {
> - switch(state){
> - case DSTATE_INITIAL:
> - if ( *p == ':' ) {
> - *p = '\0';
> - if ( !strcmp(tok, "phy") ) {
> - state = DSTATE_PHYSPATH;
> - disk->format = DISK_FORMAT_RAW;
> - disk->backend = DISK_BACKEND_BLKBACK;
> - }else if ( !strcmp(tok, "file") ) {
> - state = DSTATE_PHYSPATH;
> - disk->format = DISK_FORMAT_RAW;
> - disk->backend = DISK_BACKEND_TAPDISK2;
> - }else if ( !strcmp(tok, "tap") ) {
> - state = DSTATE_TAP;
> - }else{
> - fprintf(stderr, "Unknown disk type: %s\n", tok);
> - return 0;
> + for ( substr = strrchr(buf2, ',');
> + substr || (!substr && state == DSTATE_VDEV_PARSED);
> + substr = strrchr(buf2, ',') ) {
> + switch ( state ) {
> + case DSTATE_INITIAL: {
> + if ( !substr ) {
> + LOG("Invalid disk configuration option %s. Refer to the
> xl disk "
> + "configuration document for further information", buf2);
> + return ERROR_INVAL;
> }
> - tok = p + 1;
> - } else if (*p == ',') {
> - state = DSTATE_VIRTPATH;
> - disk->backend = DISK_FORMAT_EMPTY;
> - disk->pdev_path = strdup("");
> - tok = p + 1;
> - }
> - break;
> - case DSTATE_TAP:
> - if ( *p == ':' ) {
> - *p = '\0';
> - if ( !strcmp(tok, "aio") ) {
> - disk->format = DISK_FORMAT_RAW;
> - disk->backend = DISK_BACKEND_TAPDISK2;
> - }else if ( !strcmp(tok, "vhd") ) {
> - disk->format = DISK_FORMAT_VHD;
> - disk->backend = DISK_BACKEND_TAPDISK2;
> - }else if ( !strcmp(tok, "qcow") ) {
> - disk->format = DISK_FORMAT_QCOW;
> - disk->backend = DISK_BACKEND_QEMU;
> - }else if ( !strcmp(tok, "qcow2") ) {
> - disk->format = DISK_FORMAT_QCOW2;
> - disk->backend = DISK_BACKEND_QEMU;
> - }else {
> - fprintf(stderr, "Unknown tapdisk type: %s\n", tok);
> - return 0;
> - }
> -
> - tok = p + 1;
> - state = DSTATE_PHYSPATH;
> - }
> - break;
> - case DSTATE_PHYSPATH:
> - if ( *p == ',' ) {
> - int ioemu_len;
> -
> - *p = '\0';
> - disk->pdev_path = (*tok) ? strdup(tok) : NULL;
> - tok = p + 1;
> -
> - /* hack for ioemu disk spec */
> - ioemu_len = strlen("ioemu:");
> - state = DSTATE_VIRTPATH;
> - if ( tok + ioemu_len < end &&
> - !strncmp(tok, "ioemu:", ioemu_len)) {
> - tok += ioemu_len;
> - p += ioemu_len;
> - }
> - }
> - break;
> - case DSTATE_VIRTPATH:
> - if ( *p == ',' || *p == ':' || *p == '\0' ) {
> - switch(*p) {
> - case ':':
> - state = DSTATE_VIRTTYPE;
> - break;
> - case ',':
> - state = DSTATE_RW;
> - break;
> - case '\0':
> - state = DSTATE_TERMINAL;
> - break;
> - }
> - if ( tok == p )
> - goto out;
> - *p = '\0';
> - disk->vdev = (*tok) ? strdup(tok) : NULL;
> - tok = p + 1;
> + *substr = '\0';
> + substr++;
> + ret_val = parse_disk_attrib(disk, substr);
> + if ( ret_val )
> + return ret_val;
> + state = DSTATE_ATTRIB_PARSED;
> + break;
> }
> - break;
> - case DSTATE_VIRTTYPE:
> - if ( *p == ',' || *p == '\0' ) {
> - *p = '\0';
> - if ( !strcmp(tok, "cdrom") ) {
> - disk->is_cdrom = 1;
> - disk->unpluggable = 1;
> - }else{
> - fprintf(stderr, "Unknown virtual disk type: %s\n", tok);
> - return 0;
> + case DSTATE_ATTRIB_PARSED: {
> + if ( !substr ) {
> + LOG("Required vdev info missing in disk configuration
> option");
> + return ERROR_INVAL;
> }
> - tok = p + 1;
> - state = (*p == ',') ? DSTATE_RW : DSTATE_TERMINAL;
> + *substr = '\0';
> + substr++;
> + ret_val = parse_disk_vdev_info(disk, substr);
> + if ( ret_val )
> + return ret_val;
> + state = DSTATE_VDEV_PARSED;
> + break;
> }
> - break;
> - case DSTATE_RW:
> - if ( *p == '\0' ) {
> - disk->readwrite = (tok[0] == 'w');
> - tok = p + 1;
> - state = DSTATE_TERMINAL;
> + case DSTATE_VDEV_PARSED: {
> + ret_val = parse_disk_pdev_info(disk, buf2);
> + if ( ret_val )
> + return ret_val;
> + if ( disk->format == DISK_FORMAT_UNKNOWN )
> + disk->format = DISK_FORMAT_RAW;
> + if ( disk->backend == DISK_BACKEND_UNKNOWN )
> + disk->backend = DISK_BACKEND_TAPDISK2;
> + return 0;
> }
> - break;
> - case DSTATE_TERMINAL:
> - goto out;
> }
> }
>
> -out:
> - if ( tok != p || state != DSTATE_TERMINAL ) {
> - fprintf(stderr, "parse error in disk config near '%s'\n", tok);
> - return 0;
> - }
> -
> - return 1;
> + LOG("Disk configuration parsing failed");
> + return ERROR_INVAL;
> }
There doesn't seem to be a way to set DISK_FORMAT_EMPTY anymore, in fact
a config line like ',hdc:cdrom,w' seems to be broken.
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