Re: [Xen-devel] [PATCH v2 4/5] xenstore: make memory report available via XS_CONTROL

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Feb 21, 2017 at 04:07:36PM +0100, Juergen Gross wrote:
> Add a XS_CONTROL command to xenstored for doing a talloc report to a
> file. Right now this is supported by specifying a command line option
> when starting xenstored and sending a signal to the daemon to trigger
> the report.
> 
> To dump the report to the standard log file call:
> 
> xenstore-control memreport
> 
> To dump the report to a new file call:
> 
> xenstore-control memreport <file>
> 
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> ---
>  tools/xenstore/xenstored_control.c | 36 ++++++++++++++++++++++++++++++++++++
>  tools/xenstore/xenstored_core.c    |  2 +-
>  tools/xenstore/xenstored_core.h    |  1 +
>  3 files changed, 38 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/xenstore/xenstored_control.c 
> b/tools/xenstore/xenstored_control.c
> index c3587ad..b4ec6ce 100644
> --- a/tools/xenstore/xenstored_control.c
> +++ b/tools/xenstore/xenstored_control.c
> @@ -76,6 +76,41 @@ static int do_control_logfile(void *ctx, struct connection 
> *conn,
>       return 0;
>  }
>  
> +static int do_control_memreport(void *ctx, struct connection *conn,
> +                             char **vec, int num)
> +{
> +     FILE *fp;
> +     int fd;
> +
> +     if (num > 1)
> +             return EINVAL;
> +
> +     if (num == 0) {
> +             if (tracefd < 0) {
> +                     if (!tracefile)
> +                             return EBADF;
> +                     fp = fopen(tracefile, "a");
> +             } else {
> +                     fd = dup(tracefd);

Why dup() the fd? Is it because you want to avoid tracefd becomes
invalid under your feet?

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