Em Thu, Nov 01, 2018 at 06:00:01PM +0100, Jiri Olsa escreveu:
> 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 <[email protected]>
> Fixes: 843ff37bb59e ("perf symbols: Find symbols in different mount
> namespace")
> Link: http://lkml.kernel.org/n/[email protected]
> Signed-off-by: Jiri Olsa <[email protected]>
> ---
> 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);
Applied, and while at it I removed the needless if in the above two
lines.
> 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
