Re: [PATCH v6 15/21] tools/xl: support new 9pfs backend xen_9pfsd

[Juergen Gross <jgross@xxxxxxxx>]

On 15.02.24 07:55, Juergen Gross wrote:
> Add support for the new 9pfs backend "xen_9pfsd". For this backend type
> the tag defaults to "Xen" and the host side path to
> "/var/log/xen/guests/<dom-name>".
>
> Do most of the default settings in libxl. Unfortunately the default
> path can't easily be set in libxl, as the domain name isn't available
> in the related 9pfs specific function.
>
> Settings the defaults in libxl requires to move the sanity checking
> of 9pfs parameters from xl to libxl, too.
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> Reviewed-by: Jason Andryuk <jandryuk@xxxxxxxxx>
Sorry Anthony, just found your R-b: in my spam folder :-(


Juergen

> ---
> V2:
> - test max_files and max_open_files, too (Jason Andryuk)
> V4:
> - fix man page to use the "xen_9pfsd" type due to idl limitation
>    (Jason Andryuk)
> - set (most of) the defaults in libxl (Anthony Perard)
> ---
>   docs/man/xl.cfg.5.pod.in      | 36 +++++++++++++++++++++++++++++++++--
>   tools/libs/light/libxl_9pfs.c | 18 ++++++++++++++++++
>   tools/xl/xl_parse.c           | 23 +++++++++++++++++++---
>   3 files changed, 72 insertions(+), 5 deletions(-)
>
> diff --git a/docs/man/xl.cfg.5.pod.in b/docs/man/xl.cfg.5.pod.in
> index ea8d41727d..039e057318 100644
> --- a/docs/man/xl.cfg.5.pod.in
> +++ b/docs/man/xl.cfg.5.pod.in
> @@ -772,10 +772,16 @@ settings, from the following list:
>   
>   =over 4
>   
> +=item B<type=TYPE>
> +
> +The backendtype for the PV device. Supported values are B<qemu> and
> +B<xen_9pfsd>.  The default is B<qemu>.
> +
>   =item B<tag=STRING>
>   
>   9pfs tag to identify the filesystem share. The tag is needed on the
> -guest side to mount it.
> +guest side to mount it. For the backendtype of B<xen_9pfsd> the tag defaults to
> +"Xen".
>   
>   =item B<security_model="none">
>   
> @@ -785,12 +791,38 @@ squash or remap).
>   
>   =item B<path=STRING>
>   
> -Filesystem path on the backend to export.
> +Filesystem path on the backend to export. For the backendtype of B<xen_9pfsd>
> +the path defaults to "@XEN_LOG_DIR@/guests/<guest-name>".
>   
>   =item B<backend=domain-id>
>   
>   Specify the backend domain name or id, defaults to dom0.
>   
> +=item B<max-files=NUMBER>
> +
> +Specify the maximum number of files below B<path>. A value of 0 (which
> +is the default) doesn't limit the number of files. Only valid for
> +B<type=xen_9pfsd>.
> +
> +=item B<max-open-files=NUMBER>
> +
> +Specify the maximum number of concurrently opened files below B<path>.
> +Multiple opens of the same file are counted individually. Only valid for
> +B<type=xen_9pfsd>, which has a default of B<max-open-files=5>.
> +
> +=item B<max-space=NUMBER>
> +
> +Specify the maximum used disk space in MiB below B<path>. A value of 0 (which
> +is the default) doesn't limit the usable disk space. Only valid for
> +B<type=xen_9pfsd>.
> +
> +=item B<auto-delete=BOOLEAN>
> +
> +When set the backend will delete the oldest file which is currently not
> +opened by the guest in case the disk space limit set via B<max-space> or the
> +file limit set via B<max-files> is being reached. Only valid for
> +B<type=xen_9pfsd>.
> +
>   =back
>   
>   =item B<pvcalls=[ "backend=domain-id", ... ]>
> diff --git a/tools/libs/light/libxl_9pfs.c b/tools/libs/light/libxl_9pfs.c
> index 900c0d46a0..ddeb4f20a7 100644
> --- a/tools/libs/light/libxl_9pfs.c
> +++ b/tools/libs/light/libxl_9pfs.c
> @@ -20,6 +20,24 @@
>   static int libxl__device_p9_setdefault(libxl__gc *gc, uint32_t domid,
>                                          libxl_device_p9 *p9, bool hotplug)
>   {
> +    if (p9->type == LIBXL_P9_TYPE_UNKNOWN) {
> +        p9->type = LIBXL_P9_TYPE_QEMU;
> +    }
> +    if (p9->type == LIBXL_P9_TYPE_QEMU &&
> +        (p9->max_files || p9->max_open_files || p9->max_space ||
> +         p9->auto_delete)) {
> +        LOGD(ERROR, domid, "Illegal 9pfs parameter combination");
> +        return ERROR_INVAL;
> +    }
> +    if (p9->type == LIBXL_P9_TYPE_XEN_9PFSD && !p9->tag) {
> +        p9->tag = libxl__strdup(NOGC, "Xen");
> +    }
> +
> +    if (!p9->path || !p9->security_model || !p9->tag) {
> +        LOGD(ERROR, domid, "9pfs spec missing required field!");
> +        return ERROR_INVAL;
> +    }
> +
>       return libxl__resolve_domid(gc, p9->backend_domname, &p9->backend_domid);
>   }
>   
> diff --git a/tools/xl/xl_parse.c b/tools/xl/xl_parse.c
> index 9b358f11b8..80ffe85f5e 100644
> --- a/tools/xl/xl_parse.c
> +++ b/tools/xl/xl_parse.c
> @@ -2233,6 +2233,20 @@ void parse_config_data(const char *config_source,
>                       replace_string(&p9->tag, value);
>                   } else if (!strcmp(key, "backend")) {
>                       replace_string(&p9->backend_domname, value);
> +                } else if (!strcmp(key, "type")) {
> +                    if (libxl_p9_type_from_string(value, &p9->type)) {
> +                        fprintf(stderr, "failed to parse 9pfs type: %s\n",
> +                                value);
> +                        exit(1);
> +                    }
> +                } else if (!strcmp(key, "max-files")) {
> +                    p9->max_files = parse_ulong(value);
> +                } else if (!strcmp(key, "max-open-files")) {
> +                    p9->max_open_files = parse_ulong(value);
> +                } else if (!strcmp(key, "max-space")) {
> +                    p9->max_space = parse_ulong(value);
> +                } else if (!strcmp(key, "auto-delete")) {
> +                    p9->auto_delete = strtoul(value, NULL, 0);
>                   } else {
>                       fprintf(stderr, "Unknown 9pfs parameter '%s'\n", key);
>                       exit(1);
> @@ -2243,9 +2257,12 @@ void parse_config_data(const char *config_source,
>   
>               libxl_string_list_dispose(&pairs);
>   
> -            if (!p9->path || !p9->security_model || !p9->tag) {
> -                fprintf(stderr, "9pfs spec missing required field!\n");
> -                exit(1);
> +            if (p9->type == LIBXL_P9_TYPE_XEN_9PFSD && !p9->path) {
> +                char *path;
> +
> +                xasprintf(&path, XEN_LOG_DIR "/guests/%s", c_info->name);
> +                replace_string(&p9->path, path);
> +                free(path);
>               }
>           }
>       }

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