Messages in this thread | | | Date | Fri, 16 Nov 2018 14:03:29 +0100 | From | Jiri Olsa <> | Subject | Re: [PATCH] perf tools: Restore proper cwd on return from mnt ns |
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ping
jirka
On Thu, Nov 01, 2018 at 06:00:01PM +0100, Jiri Olsa wrote: > When reporting on 'record' server we try to retrieve/use > the mnt namespace of the profiled tasks. We use following > API with cookie to hold the return namespace, roughly: > > nsinfo__mountns_enter(struct nsinfo *nsi, struct nscookie *nc) > setns(newns, 0); > ... > new ns related open.. > ... > nsinfo__mountns_exit(struct nscookie *nc) > setns(nc->oldns) > > Once finished we setns to old namespace, which also sets the > current working directory (cwd) to "/", trashing the cwd we had. > > This is mostly fine, because we use absolute paths almost everywhere, > but it screws up perf diff: > > # perf diff > failed to open perf.data: No such file or directory (try 'perf record' first) > ... > > Adding the current working directory to be part of the cookie > and restoring it in the nsinfo__mountns_exit call. > > Cc: Krister Johansen <kjlx@templeofstupid.com> > Fixes: 843ff37bb59e ("perf symbols: Find symbols in different mount namespace") > Link: http://lkml.kernel.org/n/tip-zg3vz7kjr86cco7lo91v8yhj@git.kernel.org > Signed-off-by: Jiri Olsa <jolsa@kernel.org> > --- > tools/perf/util/namespaces.c | 18 ++++++++++++++++-- > tools/perf/util/namespaces.h | 1 + > 2 files changed, 17 insertions(+), 2 deletions(-) > > diff --git a/tools/perf/util/namespaces.c b/tools/perf/util/namespaces.c > index cf8bd123cf73..fb0458b7e6aa 100644 > --- a/tools/perf/util/namespaces.c > +++ b/tools/perf/util/namespaces.c > @@ -18,6 +18,7 @@ > #include <stdio.h> > #include <string.h> > #include <unistd.h> > +#include <asm/bug.h> > > struct namespaces *namespaces__new(struct namespaces_event *event) > { > @@ -186,6 +187,7 @@ void nsinfo__mountns_enter(struct nsinfo *nsi, > char curpath[PATH_MAX]; > int oldns = -1; > int newns = -1; > + char *oldcwd = NULL; > > if (nc == NULL) > return; > @@ -199,9 +201,13 @@ void nsinfo__mountns_enter(struct nsinfo *nsi, > if (snprintf(curpath, PATH_MAX, "/proc/self/ns/mnt") >= PATH_MAX) > return; > > + oldcwd = get_current_dir_name(); > + if (!oldcwd) > + return; > + > oldns = open(curpath, O_RDONLY); > if (oldns < 0) > - return; > + goto errout; > > newns = open(nsi->mntns_path, O_RDONLY); > if (newns < 0) > @@ -210,11 +216,14 @@ void nsinfo__mountns_enter(struct nsinfo *nsi, > if (setns(newns, CLONE_NEWNS) < 0) > goto errout; > > + nc->oldcwd = oldcwd; > nc->oldns = oldns; > nc->newns = newns; > return; > > errout: > + if (oldcwd) > + free(oldcwd); > if (oldns > -1) > close(oldns); > if (newns > -1) > @@ -223,11 +232,16 @@ void nsinfo__mountns_enter(struct nsinfo *nsi, > > void nsinfo__mountns_exit(struct nscookie *nc) > { > - if (nc == NULL || nc->oldns == -1 || nc->newns == -1) > + if (nc == NULL || nc->oldns == -1 || nc->newns == -1 || !nc->oldcwd) > return; > > setns(nc->oldns, CLONE_NEWNS); > > + if (nc->oldcwd) { > + WARN_ON_ONCE(chdir(nc->oldcwd)); > + free(nc->oldcwd); > + } > + > if (nc->oldns > -1) { > close(nc->oldns); > nc->oldns = -1; > diff --git a/tools/perf/util/namespaces.h b/tools/perf/util/namespaces.h > index cae1a9a39722..d5f46c09ea31 100644 > --- a/tools/perf/util/namespaces.h > +++ b/tools/perf/util/namespaces.h > @@ -38,6 +38,7 @@ struct nsinfo { > struct nscookie { > int oldns; > int newns; > + char *oldcwd; > }; > > int nsinfo__init(struct nsinfo *nsi); > -- > 2.17.2 >
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