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From: tip-bot for Jiri Olsa <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: peterz@infradead.org, mingo@kernel.org,
	linux-kernel@vger.kernel.org, namhyung@kernel.org,
	jolsa@kernel.org, alexander.shishkin@linux.intel.com,
	acme@redhat.com, tglx@linutronix.de, kjlx@templeofstupid.com,
	hpa@zytor.com
Subject: [tip:perf/urgent] perf tools: Restore proper cwd on return from mnt namespace
Date: Wed, 21 Nov 2018 07:02:12 -0800	[thread overview]
Message-ID: <tip-b01c1f69c8660eaeab7d365cd570103c5c073a02@git.kernel.org> (raw)
In-Reply-To: <20181101170001.30019-1-jolsa@kernel.org>

Commit-ID:  b01c1f69c8660eaeab7d365cd570103c5c073a02
Gitweb:     https://git.kernel.org/tip/b01c1f69c8660eaeab7d365cd570103c5c073a02
Author:     Jiri Olsa <jolsa@kernel.org>
AuthorDate: Thu, 1 Nov 2018 18:00:01 +0100
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 19 Nov 2018 12:12:26 -0800

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: 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>
---
 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 cf8bd123cf73..aed170bd4384 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 +216,13 @@ 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)
@@ -223,11 +231,16 @@ errout:
 
 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 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);

      parent reply	other threads:[~2018-11-21 15:02 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-01 17:00 [PATCH] perf tools: Restore proper cwd on return from mnt ns Jiri Olsa
2018-11-16 13:03 ` Jiri Olsa
2018-11-16 18:31 ` Arnaldo Carvalho de Melo
2018-11-16 18:42   ` Arnaldo Carvalho de Melo
2018-11-17  9:00     ` Jiri Olsa
2018-11-19 16:10 ` Arnaldo Carvalho de Melo
2018-11-20 10:56   ` Jiri Olsa
2018-11-20 11:23     ` [PATCHv2] " Jiri Olsa
2018-11-20 15:56     ` [PATCH] " Arnaldo Carvalho de Melo
2018-11-20 17:42       ` Jiri Olsa
2018-11-21 15:02 ` tip-bot for Jiri Olsa [this message]

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