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b01c1f69c8
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: 843ff37bb5
("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>
266 lines
5.0 KiB
C
266 lines
5.0 KiB
C
/*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License, version 2, as
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* published by the Free Software Foundation.
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*
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* Copyright (C) 2017 Hari Bathini, IBM Corporation
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*/
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#include "namespaces.h"
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#include "util.h"
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#include "event.h"
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <limits.h>
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#include <sched.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <unistd.h>
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#include <asm/bug.h>
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struct namespaces *namespaces__new(struct namespaces_event *event)
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{
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struct namespaces *namespaces;
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u64 link_info_size = ((event ? event->nr_namespaces : NR_NAMESPACES) *
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sizeof(struct perf_ns_link_info));
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namespaces = zalloc(sizeof(struct namespaces) + link_info_size);
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if (!namespaces)
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return NULL;
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namespaces->end_time = -1;
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if (event)
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memcpy(namespaces->link_info, event->link_info, link_info_size);
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return namespaces;
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}
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void namespaces__free(struct namespaces *namespaces)
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{
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free(namespaces);
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}
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int nsinfo__init(struct nsinfo *nsi)
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{
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char oldns[PATH_MAX];
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char spath[PATH_MAX];
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char *newns = NULL;
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char *statln = NULL;
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struct stat old_stat;
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struct stat new_stat;
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FILE *f = NULL;
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size_t linesz = 0;
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int rv = -1;
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if (snprintf(oldns, PATH_MAX, "/proc/self/ns/mnt") >= PATH_MAX)
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return rv;
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if (asprintf(&newns, "/proc/%d/ns/mnt", nsi->pid) == -1)
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return rv;
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if (stat(oldns, &old_stat) < 0)
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goto out;
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if (stat(newns, &new_stat) < 0)
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goto out;
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/* Check if the mount namespaces differ, if so then indicate that we
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* want to switch as part of looking up dso/map data.
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*/
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if (old_stat.st_ino != new_stat.st_ino) {
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nsi->need_setns = true;
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nsi->mntns_path = newns;
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newns = NULL;
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}
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/* If we're dealing with a process that is in a different PID namespace,
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* attempt to work out the innermost tgid for the process.
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*/
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if (snprintf(spath, PATH_MAX, "/proc/%d/status", nsi->pid) >= PATH_MAX)
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goto out;
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f = fopen(spath, "r");
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if (f == NULL)
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goto out;
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while (getline(&statln, &linesz, f) != -1) {
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/* Use tgid if CONFIG_PID_NS is not defined. */
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if (strstr(statln, "Tgid:") != NULL) {
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nsi->tgid = (pid_t)strtol(strrchr(statln, '\t'),
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NULL, 10);
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nsi->nstgid = nsi->tgid;
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}
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if (strstr(statln, "NStgid:") != NULL) {
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nsi->nstgid = (pid_t)strtol(strrchr(statln, '\t'),
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NULL, 10);
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break;
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}
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}
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rv = 0;
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out:
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if (f != NULL)
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(void) fclose(f);
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free(statln);
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free(newns);
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return rv;
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}
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struct nsinfo *nsinfo__new(pid_t pid)
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{
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struct nsinfo *nsi;
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if (pid == 0)
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return NULL;
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nsi = calloc(1, sizeof(*nsi));
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if (nsi != NULL) {
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nsi->pid = pid;
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nsi->tgid = pid;
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nsi->nstgid = pid;
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nsi->need_setns = false;
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/* Init may fail if the process exits while we're trying to look
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* at its proc information. In that case, save the pid but
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* don't try to enter the namespace.
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*/
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if (nsinfo__init(nsi) == -1)
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nsi->need_setns = false;
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refcount_set(&nsi->refcnt, 1);
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}
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return nsi;
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}
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struct nsinfo *nsinfo__copy(struct nsinfo *nsi)
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{
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struct nsinfo *nnsi;
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if (nsi == NULL)
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return NULL;
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nnsi = calloc(1, sizeof(*nnsi));
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if (nnsi != NULL) {
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nnsi->pid = nsi->pid;
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nnsi->tgid = nsi->tgid;
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nnsi->nstgid = nsi->nstgid;
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nnsi->need_setns = nsi->need_setns;
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if (nsi->mntns_path) {
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nnsi->mntns_path = strdup(nsi->mntns_path);
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if (!nnsi->mntns_path) {
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free(nnsi);
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return NULL;
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}
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}
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refcount_set(&nnsi->refcnt, 1);
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}
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return nnsi;
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}
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void nsinfo__delete(struct nsinfo *nsi)
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{
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zfree(&nsi->mntns_path);
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free(nsi);
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}
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struct nsinfo *nsinfo__get(struct nsinfo *nsi)
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{
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if (nsi)
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refcount_inc(&nsi->refcnt);
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return nsi;
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}
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void nsinfo__put(struct nsinfo *nsi)
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{
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if (nsi && refcount_dec_and_test(&nsi->refcnt))
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nsinfo__delete(nsi);
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}
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void nsinfo__mountns_enter(struct nsinfo *nsi,
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struct nscookie *nc)
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{
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char curpath[PATH_MAX];
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int oldns = -1;
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int newns = -1;
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char *oldcwd = NULL;
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if (nc == NULL)
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return;
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nc->oldns = -1;
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nc->newns = -1;
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if (!nsi || !nsi->need_setns)
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return;
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if (snprintf(curpath, PATH_MAX, "/proc/self/ns/mnt") >= PATH_MAX)
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return;
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oldcwd = get_current_dir_name();
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if (!oldcwd)
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return;
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oldns = open(curpath, O_RDONLY);
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if (oldns < 0)
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goto errout;
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newns = open(nsi->mntns_path, O_RDONLY);
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if (newns < 0)
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goto errout;
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if (setns(newns, CLONE_NEWNS) < 0)
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goto errout;
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nc->oldcwd = oldcwd;
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nc->oldns = oldns;
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nc->newns = newns;
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return;
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errout:
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free(oldcwd);
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if (oldns > -1)
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close(oldns);
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if (newns > -1)
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close(newns);
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}
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void nsinfo__mountns_exit(struct nscookie *nc)
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{
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if (nc == NULL || nc->oldns == -1 || nc->newns == -1 || !nc->oldcwd)
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return;
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setns(nc->oldns, CLONE_NEWNS);
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if (nc->oldcwd) {
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WARN_ON_ONCE(chdir(nc->oldcwd));
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zfree(&nc->oldcwd);
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}
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if (nc->oldns > -1) {
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close(nc->oldns);
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nc->oldns = -1;
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}
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if (nc->newns > -1) {
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close(nc->newns);
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nc->newns = -1;
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}
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}
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char *nsinfo__realpath(const char *path, struct nsinfo *nsi)
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{
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char *rpath;
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struct nscookie nsc;
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nsinfo__mountns_enter(nsi, &nsc);
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rpath = realpath(path, NULL);
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nsinfo__mountns_exit(&nsc);
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return rpath;
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}
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