From: Jiri Olsa jolsa@kernel.org
[ Upstream commit b01c1f69c8660eaeab7d365cd570103c5c073a02 ]
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.
Signed-off-by: Jiri Olsa jolsa@kernel.org Cc: Alexander Shishkin alexander.shishkin@linux.intel.com Cc: Krister Johansen kjlx@templeofstupid.com Cc: Namhyung Kim namhyung@kernel.org Cc: Peter Zijlstra peterz@infradead.org Fixes: 843ff37bb59e ("perf symbols: Find symbols in different mount namespace") Link: http://lkml.kernel.org/r/20181101170001.30019-1-jolsa@kernel.org [ No need to check for NULL args for free(), use zfree() for struct members ] Signed-off-by: Arnaldo Carvalho de Melo acme@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- tools/perf/util/namespaces.c | 17 +++++++++++++++-- tools/perf/util/namespaces.h | 1 + 2 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/tools/perf/util/namespaces.c b/tools/perf/util/namespaces.c index 1ef0049860a8..eadc7ddacbf6 100644 --- a/tools/perf/util/namespaces.c +++ b/tools/perf/util/namespaces.c @@ -17,6 +17,7 @@ #include <stdio.h> #include <string.h> #include <unistd.h> +#include <asm/bug.h>
struct namespaces *namespaces__new(struct namespaces_event *event) { @@ -185,6 +186,7 @@ void nsinfo__mountns_enter(struct nsinfo *nsi, char curpath[PATH_MAX]; int oldns = -1; int newns = -1; + char *oldcwd = NULL;
if (nc == NULL) return; @@ -198,9 +200,13 @@ 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) @@ -209,11 +215,13 @@ 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: + free(oldcwd); if (oldns > -1) close(oldns); if (newns > -1) @@ -222,11 +230,16 @@ 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)); + zfree(&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 05d82601c9a6..23584a6dd048 100644 --- a/tools/perf/util/namespaces.h +++ b/tools/perf/util/namespaces.h @@ -36,6 +36,7 @@ struct nsinfo { struct nscookie { int oldns; int newns; + char *oldcwd; };
int nsinfo__init(struct nsinfo *nsi);