Re: [PATCH v2 27/29] tools/xenstored: add helpers for filename handling

[Julien Grall <julien@xxxxxxx>]

Hi Juergen,

On 10/11/2023 16:08, Juergen Gross wrote:
> Add some helpers for handling filenames which might need different
> implementations between stubdom and daemon environments:
>
> - expansion of relative filenames (those are not really defined today,
>    just expand them to be relative to /var/lib/xen/xenstore)
> - expansion of xenstore_daemon_rundir() (used e.g. for saving the state
>    file in case of live update - needs to be unchanged in the daemon
>    case, but should result in /var/lib/xen/xenstore for stubdom)
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> Reviewed-by: Jason Andryuk <jandryuk@xxxxxxxxx>
> ---
>   tools/xenstored/core.c      | 9 ++++++++-
>   tools/xenstored/core.h      | 3 +++
>   tools/xenstored/lu_daemon.c | 4 ++--
>   tools/xenstored/minios.c    | 5 +++++
>   tools/xenstored/posix.c     | 5 +++++
>   5 files changed, 23 insertions(+), 3 deletions(-)
>
> diff --git a/tools/xenstored/core.c b/tools/xenstored/core.c
> index 4a9d874f17..77befd24c9 100644
> --- a/tools/xenstored/core.c
> +++ b/tools/xenstored/core.c
> @@ -158,6 +158,13 @@ void trace_destroy(const void *data, const char *type)
>                 trace("obj: DESTROY %s %p\n", type, data);
>   }
>   
> +char *absolute_filename(const void *ctx, const char *filename)
Can the return be const?

> +{
> +       if (filename[0] != '/')
> +               return talloc_asprintf(ctx, XENSTORE_LIB_DIR "/%s", filename);
Looking at the rest of patch, you will be using xenstore_rundir(). I 
wonder whether it would not be better to switch to xenstore_rundir() so...
> +       return talloc_strdup(ctx, filename);
> +}
> +
>   /**
>    * Signal handler for SIGHUP, which requests that the trace log is reopened
>    * (in the main loop).  A single byte is written to reopen_log_pipe, to awaken
> @@ -2983,7 +2990,7 @@ int main(int argc, char *argv[])
>   
>   	signal(SIGHUP, trigger_reopen_log);
>         if (tracefile)
> -               tracefile = talloc_strdup(NULL, tracefile);
> +               tracefile = absolute_filename(NULL, tracefile);
>   
>   #ifndef NO_LIVE_UPDATE
>         /* Read state in case of live update. */
> diff --git a/tools/xenstored/core.h b/tools/xenstored/core.h
> index a0d3592961..51e1dddb22 100644
> --- a/tools/xenstored/core.h
> +++ b/tools/xenstored/core.h
> @@ -393,6 +393,9 @@ void early_init(void);
>   void mount_9pfs(void);
>   #endif
>   
> +const char *xenstore_rundir(void);
> +char *absolute_filename(const void *ctx, const char *filename);
> +
>   /* Write out the pidfile */
>   void write_pidfile(const char *pidfile);
>   
> diff --git a/tools/xenstored/lu_daemon.c b/tools/xenstored/lu_daemon.c
> index 71bcabadd3..6351111ab0 100644
> --- a/tools/xenstored/lu_daemon.c
> +++ b/tools/xenstored/lu_daemon.c
> @@ -24,7 +24,7 @@ void lu_get_dump_state(struct lu_dump_state *state)
>         state->size = 0;
>   
>   	state->filename = talloc_asprintf(NULL, "%s/state_dump",
> -                                         xenstore_daemon_rundir());
> +                                         xenstore_rundir());
... call and ...

>         if (!state->filename)
>                 barf("Allocation failure");
>   
> @@ -65,7 +65,7 @@ FILE *lu_dump_open(const void *ctx)
>         int fd;
>   
>   	filename = talloc_asprintf(ctx, "%s/state_dump",
> -                                  xenstore_daemon_rundir());
> +                                  xenstore_rundir());
... this one could be replaced with absolute_filename().

>         if (!filename)
>                 return NULL;
>   
> diff --git a/tools/xenstored/minios.c b/tools/xenstored/minios.c
> index fddbede869..cfc2377857 100644
> --- a/tools/xenstored/minios.c
> +++ b/tools/xenstored/minios.c
> @@ -98,3 +98,8 @@ void mount_9pfs(void)
>   {
>         create_thread("mount-9pfs", mount_thread, NULL);
>   }
> +
> +const char *xenstore_rundir(void)
> +{
> +       return XENSTORE_LIB_DIR;
> +}
> diff --git a/tools/xenstored/posix.c b/tools/xenstored/posix.c
> index fcb7791bd7..76f5c9ab84 100644
> --- a/tools/xenstored/posix.c
> +++ b/tools/xenstored/posix.c
> @@ -168,3 +168,8 @@ void early_init(void)
>         mkdir(xenstore_daemon_rundir(), 0755);
>         mkdir(XENSTORE_LIB_DIR, 0755);
>   }
> +
> +const char *xenstore_rundir(void)
> +{
> +       return xenstore_daemon_rundir();
> +}
Cheers,

--
Julien Grall