Re: [Xen-devel] [PATCH 2 of 2] xl: Make clear distinction between "filename" and "data source"

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

On 03/04/12 19:28, George Dunlap wrote:
> Many places in xl there's a variable or element named "filename" which
> does not contain a filename, but the source of the data for reporting
> purposes.  Worse, there are variables which are sometimes actually
> used or interpreted as a filename depending on what other variables
> are set.  This makes it difficult to tell when a string is purely
> cosmetic, and when another bit of code may actually attempt to call
> "open" with the string.
>
> This patch makes a consistent distinction between "filename" (which
> always refers to the name of an actual file, and may be interpreted as
> such at some point) and "source" (which may be a filename, or may be
> another data source such as a migration stream or saved data).
>
> This does add some variables and reshuffle where assignments happen;
> most notably, the "restore_filename" element of struct domain_create
> is now only set when restoring from a file.
>
> But at a high level, there should be no funcitonal changes.
>
> Signed-off-by: George Dunlap<george.dunlap@xxxxxxxxxxxxx>
Sorry, this was meant to be an RFC patch before I did more thorough 
testing to make sure there aren't actually any regressions. Please give 
your opinions but do not apply yet.
> diff -r 5ca90c805046 -r 30cc13e25e01 tools/libxl/libxl_utils.c
> --- a/tools/libxl/libxl_utils.c Tue Apr 03 18:00:24 2012 +0100
> +++ b/tools/libxl/libxl_utils.c Tue Apr 03 19:02:19 2012 +0100
> @@ -334,7 +334,7 @@ int libxl_read_file_contents(libxl_ctx *
>                                                                             \
>     int libxl_##rw##_exactly(libxl_ctx *ctx, int fd,                 \
>                              constdata void *data, ssize_t sz,              \
> -                           const char *filename, const char *what) {      \
> +                           const char *source, const char *what) {      \
>         ssize_t got;                                                        \
>                                                                             \
>         while (sz>  0) {                                                    \
> @@ -343,7 +343,7 @@ int libxl_read_file_contents(libxl_ctx *
>                 if (errno == EINTR) continue;                               \
>                 if (!ctx) return errno;                                     \
>                 LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "failed to " #rw " 
> %s%s%s", \
> -                           what?what:"", what?" from ":"", filename);     \
> +                           what?what:"", what?" from ":"", source);       \
>                 return errno;                                               \
>             }                                                               \
>             if (got == 0) {                                                 \
> @@ -352,7 +352,7 @@ int libxl_read_file_contents(libxl_ctx *
>                        zero_is_eof                                          \
>                        ? "file/stream truncated reading %s%s%s"             \
>                        : "file/stream write returned 0! writing %s%s%s",    \
> -                     what?what:"", what?" from ":"", filename);           \
> +                     what?what:"", what?" from ":"", source);             \
>                 return EPROTO;                                              \
>             }                                                               \
>             sz -= got;                                                      \
> diff -r 5ca90c805046 -r 30cc13e25e01 tools/libxl/xl_cmdimpl.c
> --- a/tools/libxl/xl_cmdimpl.c  Tue Apr 03 18:00:24 2012 +0100
> +++ b/tools/libxl/xl_cmdimpl.c  Tue Apr 03 19:02:19 2012 +0100
> @@ -507,9 +507,9 @@ vcpp_out:
>       return rc;
>   }
>
> -static void parse_config_data(const char *configfile_filename_report,
> -                              const char *configfile_data,
> -                              int configfile_len,
> +static void parse_config_data(const char *config_source,
> +                              const char *config_data,
> +                              int config_len,
>                                 libxl_domain_config *d_config)
>   {
>       const char *buf;
> @@ -524,15 +524,15 @@ static void parse_config_data(const char
>       libxl_domain_create_info *c_info =&d_config->c_info;
>       libxl_domain_build_info *b_info =&d_config->b_info;
>
> -    config= xlu_cfg_init(stderr, configfile_filename_report);
> +    config= xlu_cfg_init(stderr, config_source);
>       if (!config) {
>           fprintf(stderr, "Failed to allocate for configuration\n");
>           exit(1);
>       }
>
> -    e= xlu_cfg_readdata(config, configfile_data, configfile_len);
> +    e= xlu_cfg_readdata(config, config_data, config_len);
>       if (e) {
> -        fprintf(stderr, "Failed to parse config file: %s\n", strerror(e));
> +        fprintf(stderr, "Failed to parse config: %s\n", strerror(e));
>           exit(1);
>       }
>
> @@ -1467,6 +1467,8 @@ static int create_domain(struct domain_c
>       const char *config_file = dom_info->config_file;
>       const char *extra_config = dom_info->extra_config;
>       const char *restore_file = dom_info->restore_file;
> +    const char *config_source = NULL;
> +    const char *restore_source = NULL;
>       int migrate_fd = dom_info->migrate_fd;
>
>       int i;
> @@ -1482,24 +1484,28 @@ static int create_domain(struct domain_c
>       pid_t child_console_pid = -1;
>       struct save_file_header hdr;
>
> +    int restoring = (restore_file || (migrate_fd>= 0));
> +
>       memset(&d_config, 0x00, sizeof(d_config));
>
> -    if (restore_file) {
> +    if (restoring) {
>           uint8_t *optdata_begin = 0;
>           const uint8_t *optdata_here = 0;
>           union { uint32_t u32; char b[4]; } u32buf;
>           uint32_t badflags;
>
>           if (migrate_fd>= 0) {
> +            restore_source = "incoming migration stream";
>               restore_fd = migrate_fd;
>           } else {
> +            restore_source = restore_file;
>               restore_fd = open(restore_file, O_RDONLY);
>               rc = libxl_fd_set_cloexec(ctx, restore_fd, 1);
>               if (rc) return rc;
>           }
>
>           CHK_ERRNO( libxl_read_exactly(ctx, restore_fd,&hdr,
> -                   sizeof(hdr), restore_file, "header") );
> +                   sizeof(hdr), restore_source, "header") );
>           if (memcmp(hdr.magic, savefileheader_magic, sizeof(hdr.magic))) {
>               fprintf(stderr, "File has wrong magic number -"
>                       " corrupt or for a different tool?\n");
> @@ -1512,7 +1518,7 @@ static int create_domain(struct domain_c
>           fprintf(stderr, "Loading new save file %s"
>                   " (new xl fmt info"
>                   " 0x%"PRIx32"/0x%"PRIx32"/%"PRIu32")\n",
> -                restore_file, hdr.mandatory_flags, hdr.optional_flags,
> +                restore_source, hdr.mandatory_flags, hdr.optional_flags,
>                   hdr.optional_data_len);
>
>           badflags = hdr.mandatory_flags&  ~( 0 /* none understood yet */ );
> @@ -1525,7 +1531,7 @@ static int create_domain(struct domain_c
>           if (hdr.optional_data_len) {
>               optdata_begin = xmalloc(hdr.optional_data_len);
>               CHK_ERRNO( libxl_read_exactly(ctx, restore_fd, optdata_begin,
> -                   hdr.optional_data_len, restore_file, "optdata") );
> +                   hdr.optional_data_len, restore_source, "optdata") );
>           }
>
>   #define OPTDATA_LEFT  (hdr.optional_data_len - (optdata_here - optdata_begin))
> @@ -1560,7 +1566,7 @@ static int create_domain(struct domain_c
>                                          &config_data,&config_len);
>           if (ret) { fprintf(stderr, "Failed to read config file: %s: %s\n",
>                              config_file, strerror(errno)); return ERROR_FAIL; }
> -        if (!restore_file&&  extra_config&&  strlen(extra_config)) {
> +        if (!restoring&&  extra_config&&  strlen(extra_config)) {
>               if (config_len>  INT_MAX - (strlen(extra_config) + 2 + 1)) {
>                   fprintf(stderr, "Failed to attach extra configration\n");
>                   return ERROR_FAIL;
> @@ -1575,19 +1581,20 @@ static int create_domain(struct domain_c
>               config_len += sprintf(config_data + config_len, "\n%s\n",
>                   extra_config);
>           }
> +        config_source=config_file;
>       } else {
>           if (!config_data) {
>               fprintf(stderr, "Config file not specified and"
>                       " none in save file\n");
>               return ERROR_INVAL;
>           }
> -        config_file = "<saved>";
> +        config_source = "<saved>";
>       }
>
>       if (!dom_info->quiet)
> -        printf("Parsing config file %s\n", config_file);
> -
> -    parse_config_data(config_file, config_data, config_len,&d_config);
> +        printf("Parsing config from %s\n", config_source);
> +
> +    parse_config_data(config_source, config_data, config_len,&d_config);
>
>       if (migrate_fd>= 0) {
>           if (d_config.c_info.name) {
> @@ -1638,7 +1645,7 @@ start:
>           cb = NULL;
>       }
>
> -    if ( restore_file ) {
> +    if ( restoring ) {
>           ret = libxl_domain_create_restore(ctx,&d_config,
>                                               cb,&child_console_pid,
>                                               &domid, restore_fd);
> @@ -2410,7 +2417,7 @@ static void list_domains_details(const l
>   {
>       libxl_domain_config d_config;
>
> -    char *config_file;
> +    char *config_source;
>       uint8_t *data;
>       int i, len, rc;
>
> @@ -2421,13 +2428,13 @@ static void list_domains_details(const l
>           rc = libxl_userdata_retrieve(ctx, info[i].domid, "xl",&data,&len);
>           if (rc)
>               continue;
> -        CHK_ERRNO(asprintf(&config_file, "<domid %d data>", info[i].domid));
> +        CHK_ERRNO(asprintf(&config_source, "<domid %d data>", info[i].domid));
>           memset(&d_config, 0x00, sizeof(d_config));
> -        parse_config_data(config_file, (char *)data, len,&d_config);
> +        parse_config_data(config_source, (char *)data, len,&d_config);
>           printf_info(default_output_format, info[i].domid,&d_config);
>           libxl_domain_config_dispose(&d_config);
>           free(data);
> -        free(config_file);
> +        free(config_source);
>       }
>   }
>
> @@ -2530,7 +2537,7 @@ static void save_domain_core_begin(const
>       }
>   }
>
> -static void save_domain_core_writeconfig(int fd, const char *filename,
> +static void save_domain_core_writeconfig(int fd, const char *source,
>                                     const uint8_t *config_data, int config_len)
>   {
>       struct save_file_header hdr;
> @@ -2559,13 +2566,13 @@ static void save_domain_core_writeconfig
>       /* that's the optional data */
>
>       CHK_ERRNO( libxl_write_exactly(ctx, fd,
> -&hdr, sizeof(hdr), filename, "header") );
> +&hdr, sizeof(hdr), source, "header") );
>       CHK_ERRNO( libxl_write_exactly(ctx, fd,
> -        optdata_begin, hdr.optional_data_len, filename, "header") );
> +        optdata_begin, hdr.optional_data_len, source, "header") );
>
>       fprintf(stderr, "Saving to %s new xl format (info"
>               " 0x%"PRIx32"/0x%"PRIx32"/%"PRIu32")\n",
> -            filename, hdr.mandatory_flags, hdr.optional_flags,
> +            source, hdr.mandatory_flags, hdr.optional_flags,
>               hdr.optional_data_len);
>   }
>
> @@ -2891,7 +2898,6 @@ static void migrate_receive(int debug, i
>       dom_info.daemonize = daemonize;
>       dom_info.monitor = monitor;
>       dom_info.paused = 1;
> -    dom_info.restore_file = "incoming migration stream";
>       dom_info.migrate_fd = 0; /* stdin */
>       dom_info.migration_domname_r =&migration_domname;
>       dom_info.incr_generationid = 0;

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