Commit b01c1f69 authored by Jiri Olsa's avatar Jiri Olsa Committed by Arnaldo Carvalho de Melo

perf tools: Restore proper cwd on return from mnt namespace

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: default avatarJiri 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: 843ff37b ("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: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 8feb8efe
...@@ -18,6 +18,7 @@ ...@@ -18,6 +18,7 @@
#include <stdio.h> #include <stdio.h>
#include <string.h> #include <string.h>
#include <unistd.h> #include <unistd.h>
#include <asm/bug.h>
struct namespaces *namespaces__new(struct namespaces_event *event) struct namespaces *namespaces__new(struct namespaces_event *event)
{ {
...@@ -186,6 +187,7 @@ void nsinfo__mountns_enter(struct nsinfo *nsi, ...@@ -186,6 +187,7 @@ void nsinfo__mountns_enter(struct nsinfo *nsi,
char curpath[PATH_MAX]; char curpath[PATH_MAX];
int oldns = -1; int oldns = -1;
int newns = -1; int newns = -1;
char *oldcwd = NULL;
if (nc == NULL) if (nc == NULL)
return; return;
...@@ -199,9 +201,13 @@ void nsinfo__mountns_enter(struct nsinfo *nsi, ...@@ -199,9 +201,13 @@ void nsinfo__mountns_enter(struct nsinfo *nsi,
if (snprintf(curpath, PATH_MAX, "/proc/self/ns/mnt") >= PATH_MAX) if (snprintf(curpath, PATH_MAX, "/proc/self/ns/mnt") >= PATH_MAX)
return; return;
oldcwd = get_current_dir_name();
if (!oldcwd)
return;
oldns = open(curpath, O_RDONLY); oldns = open(curpath, O_RDONLY);
if (oldns < 0) if (oldns < 0)
return; goto errout;
newns = open(nsi->mntns_path, O_RDONLY); newns = open(nsi->mntns_path, O_RDONLY);
if (newns < 0) if (newns < 0)
...@@ -210,11 +216,13 @@ void nsinfo__mountns_enter(struct nsinfo *nsi, ...@@ -210,11 +216,13 @@ void nsinfo__mountns_enter(struct nsinfo *nsi,
if (setns(newns, CLONE_NEWNS) < 0) if (setns(newns, CLONE_NEWNS) < 0)
goto errout; goto errout;
nc->oldcwd = oldcwd;
nc->oldns = oldns; nc->oldns = oldns;
nc->newns = newns; nc->newns = newns;
return; return;
errout: errout:
free(oldcwd);
if (oldns > -1) if (oldns > -1)
close(oldns); close(oldns);
if (newns > -1) if (newns > -1)
...@@ -223,11 +231,16 @@ void nsinfo__mountns_enter(struct nsinfo *nsi, ...@@ -223,11 +231,16 @@ void nsinfo__mountns_enter(struct nsinfo *nsi,
void nsinfo__mountns_exit(struct nscookie *nc) 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; return;
setns(nc->oldns, CLONE_NEWNS); setns(nc->oldns, CLONE_NEWNS);
if (nc->oldcwd) {
WARN_ON_ONCE(chdir(nc->oldcwd));
zfree(&nc->oldcwd);
}
if (nc->oldns > -1) { if (nc->oldns > -1) {
close(nc->oldns); close(nc->oldns);
nc->oldns = -1; nc->oldns = -1;
......
...@@ -38,6 +38,7 @@ struct nsinfo { ...@@ -38,6 +38,7 @@ struct nsinfo {
struct nscookie { struct nscookie {
int oldns; int oldns;
int newns; int newns;
char *oldcwd;
}; };
int nsinfo__init(struct nsinfo *nsi); int nsinfo__init(struct nsinfo *nsi);
......
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