[lxc-devel] [PATCH 1/2 v2] Add clone_update_unexp_ovl_dir() function
Serge Hallyn
serge.hallyn at ubuntu.com
Fri Oct 30 15:55:06 UTC 2015
Quoting Christian Brauner (christianvanbrauner at gmail.com):
> On Oct 30, 2015 4:08 PM, "Serge Hallyn" <serge.hallyn at ubuntu.com> wrote:
> >
> > Quoting Christian Brauner (christianvanbrauner at gmail.com):
> > > This functions updates absolute paths for overlay upper- and workdirs
> so users
> > > can simply clone and start new containers without worrying about
> absolute paths
> > > in lxc.mount.entry overlay entries.
> > >
> > > Signed-off-by: Christian Brauner <christianvanbrauner at gmail.com>
> > > ---
> > > src/lxc/confile.c | 103
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > > src/lxc/confile.h | 3 ++
> > > 2 files changed, 106 insertions(+)
> > >
> > > diff --git a/src/lxc/confile.c b/src/lxc/confile.c
> > > index f7d6814..bc5b7ef 100644
> > > --- a/src/lxc/confile.c
> > > +++ b/src/lxc/confile.c
> > > @@ -2598,6 +2598,109 @@ void clear_unexp_config_line(struct lxc_conf
> *conf, const char *key, bool rm_sub
> > > }
> > > }
> > >
> > > +bool clone_update_unexp_ovl_dir(struct lxc_conf *conf, const char
> *oldpath,
> > > + const char *newpath, const char *oldname,
> > > + const char *newname, const char *ovldir)
> > > +{
> > > + const char *key = "lxc.mount.entry";
> > > + int ret;
> > > + char *lstart = conf->unexpanded_config;
> > > + char *lend;
> > > + char *p;
> > > + char *q;
> > > + size_t newdirlen = strlen(ovldir) + strlen(newpath) +
> strlen(newname) + 2;
> > > + size_t olddirlen = strlen(ovldir) + strlen(oldpath) +
> strlen(oldname) + 2;
> > > + char *olddir = alloca(olddirlen + 1);
> > > + char *newdir = alloca(newdirlen + 1);
> > > +
> > > + ret = snprintf(olddir, olddirlen + 1, "%s=%s/%s", ovldir,
> oldpath, oldname);
> > > + if (ret < 0 || ret >= olddirlen + 1) {
> > > + ERROR("Bug in %s", __func__);
> > > + return false;
> > > + }
> > > + ret = snprintf(newdir, newdirlen + 1, "%s=%s/%s", ovldir,
> newpath, newname);
> > > + if (ret < 0 || ret >= newdirlen + 1) {
> > > + ERROR("Bug in %s", __func__);
> > > + return false;
> > > + }
> > > + if (!conf->unexpanded_config)
> > > + return true;
> > > + while (*lstart) {
> > > + lend = strchr(lstart, '\n');
> > > + if (!lend)
> > > + lend = lstart + strlen(lstart);
> > > + else
> > > + lend++;
> > > + if (strncmp(lstart, key, strlen(key)) != 0) {
> > > + lstart = lend;
> > > + continue;
> > > + }
> > > + p = strchr(lstart + strlen(key), '=');
> > > + if (!p) {
> > > + lstart = lend;
> > > + continue;
> > > + }
> > > + p++;
> > > + while (isblank(*p))
> > > + p++;
> > > + if (!*p)
> > > + return true;
> >
> > I think you should
> >
> > if (p >= lend)
> > continue;
> >
> > (and then you can skip the !*p check above as this should catch that)
> >
> > What you have will only get confused on invalid configs, but this would
> > be stricter and make me feel better.
>
> Agreed. Than we should change that in the other function
> (clone_update_unexp_hooks()) as well.
>
> >
> > > + /* We check that when an lxc.mount.entry is found the
> substrings
> > > + * " overlay " or " aufs " are present before we try to
> update
> > > + * the line. This seems like a bit more safety. We can
> check for
> > > + * " overlay " and " aufs " since both substrings need to
> have
> > > + * at least one space before and after them. When the
> space
> > > + * before or after is missing it is very likely that these
> > > + * substrings are part of a path or something else. So we
> > > + * shouldn't bother to do any further work...
> > > + */
> > > + if (!strstr(p, " overlay ") && !strstr(p, " aufs ")) {
> > > + lstart = lend;
> > > + continue;
> > > + }
> >
> > But this will find " overlay " in any subsequent lines too right? Don't
> you
> > need to limit your search to the line? Maybe by saving *lend and setting
> > *lend = '\0'?
>
> But we do want to check in all lines, don't we? If we do not find the
> substring in the current line we skip it and check the next one.
Right, so the you set *lend back to the saved *lend before going to the
top of the loop - there's someplace else i lxc that does this.
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