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

[Juergen Gross <jgross@xxxxxxxx>]

On 13.11.23 23:25, Julien Grall wrote:
> 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?
I'll have a look.

> > +{
> > +    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().
No, I don't think this is a good idea.

I don't want the daemon to store trace files specified as relative files
to be stored in /var/run/xen, while I want all files of the stubdom to be
stored under /var/lib/xen.


Juergen

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