Re: [Xen-devel] [PATCH] tools/xenstore: Do not abort xenstore-ls if a node disappears while iterating

[David Woodhouse <dwmw2@xxxxxxxxxxxxx>]

On Mon, 2019-03-04 at 14:18 +0000, Wei Liu wrote:
> CC Ian as well.
> 
> It would be better if you run ./scripts/get_maintainers.pl on your
> patches in the future to CC the correct people.

Will do; thanks.

> On Fri, Mar 01, 2019 at 12:16:56PM +0000, David Woodhouse wrote:
> > From: David Woodhouse <dwmw@xxxxxxxxxxxx>
> > 
> > When recursing, a node sometimes disappears. Deal with it and move on
> > instead of aborting and failing to print the rest of what was
> > requested.
> >     
> > Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
> > ---
> > And thus did an extremely sporadic "not going to delete that device
> > because it already doesn't exist" failure mode become painfully obvious
> > in retrospect...
> > 
> > diff --git a/tools/xenstore/xenstore_client.c
> > b/tools/xenstore/xenstore_client.c
> > index 3afc630ab8..c089d60a2a 100644
> > --- a/tools/xenstore/xenstore_client.c
> > +++ b/tools/xenstore/xenstore_client.c
> > @@ -153,8 +153,13 @@ static void do_ls(struct xs_handle *h, char
> > *path,
> > int cur_depth, int show_perms
> >        err(1, "malloc in do_ls");
> >  
> >      e = xs_directory(h, XBT_NULL, path, &num);
> > -    if (e == NULL)
> > -        err(1, "xs_directory (%s)", path);
> > +    if (e == NULL) {
> > +        if (!cur_depth)
> > +            err(1, "xs_directory (%s)", path);
> > +
> > +        /* If a node disappears while recursing, silently move on.
> > */
> > +        num = 0;
> > +    }
> 
> Can you check if the errno is ENOENT? I would rather not ignore other
> types of errors if possible.

Under what circumstances is it correct for xenstore-ls to abort
immediately and not attempt to print anything more?

I'm sure there are circumstances where the world is so hosed that it'll
keep getting errors and *fail* to print anything more. But to
deliberately bail out? Should that really be restricted to ENOENT?

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