Re: [PATCH for-4.6] xenstored: log tdb message via xenstored's logging mechanisms

[Ian Campbell <Ian.Campbell@citrix.com>]

On Thu, 2015-01-08 at 12:57 +0000, Wei Liu wrote:
> On Thu, Jan 08, 2015 at 12:33:29PM +0000, Ian Campbell wrote:
> > ping.
> > 
> > On Mon, 2014-12-15 at 13:18 +0000, Ian Campbell wrote:
> > > TDB provides us with a callback for this purpose. Use it in both
> > > xenstored and xs_tdb_dump.
> > > 
> > > While at it make the existing log() macro tollerate memory failures.
> > > 
> > > Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> > > ---
> > >  tools/xenstore/xenstored_core.c |   39 +++++++++++++++++++++++++++++++++------
> > >  tools/xenstore/xs_tdb_dump.c    |   12 +++++++++++-
> > >  2 files changed, 44 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
> > > index 4eaff57..3fd9a20 100644
> > > --- a/tools/xenstore/xenstored_core.c
> > > +++ b/tools/xenstore/xenstored_core.c
> > > @@ -89,9 +89,14 @@ static void check_store(void);
> > >  #define log(...)							\
> > >  	do {								\
> > >  		char *s = talloc_asprintf(NULL, __VA_ARGS__);		\
> > > -		trace("%s\n", s);					\
> > > -		syslog(LOG_ERR, "%s",  s);				\
> > > -		talloc_free(s);						\
> > > +		if (s) {						\
> > > +			trace("%s\n", s);				\
> > > +			syslog(LOG_ERR, "%s",  s);			\
> > > +			talloc_free(s);					\
> > > +		} else {						\
> > > +			trace("talloc failure during logging\n");	\
> > > +			syslog(LOG_ERR, "talloc failure during logging\n"); \
> > > +		}							\
> 
> talloc_free can tolerate NULL pointer.

Good point, I'll fix. I think I'll also change the message to more
clearly indicate an allocation failure, since that is what has actually
happened.

> > >  	} while (0)
> > >  
> [...]
> > > +		tdb_ctx = tdb_open_ex(tdbname, 0, tdb_flags, O_RDWR, 0,
> > > +				      &tdb_logger, NULL);
> [...]
> > > +		tdb_ctx = tdb_open_ex(tdbname, 7919, tdb_flags, O_RDWR|O_CREAT,
> > > +				      0640, &tdb_logger, NULL);
> [...]
> > > +	tdb = tdb_open_ex(talloc_strdup(NULL, argv[1]), 0, 0, O_RDONLY, 0,
> > > +			  tdb_logger, NULL);
> 
> Should be &tdb_logger?

tdb_logger is a function, so it's not strictly required, but it is good
form (and a hint to the reader) plus inconsistent with the others, so
I'll change.

Ian.