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SubjectRe: lost path_put in perf_fill_ns_link_info
Hi Vasily and all,

The patch looks correct for me. I tried to reproduce this issue and
checked that this patch fixes it. Bellow you can find my test program
and a command line to run it. The problem still exists even with this patch.

$ cat test.c
#define _GNU_SOURCE
#include <sched.h>

int main(int argc, char **argv)
{
while (1)
unshare(CLONE_NEWUTS);
return 0;
}

$ gcc -o test_unshare test.c
$ for i in `seq 10000`; do perf trace -o log unshare -u true; done &
[5] 28766
$ for i in `seq 10000`; do perf trace -o log unshare -u true; done &
[6] 28840

$ echo 3 > /proc/sys/vm/drop_caches | cat /proc/slabinfo | grep dentry
dentry 74848 78660 224 18 1 : tunables 0 0 0 : slabdata 4370 4370 0

$ sleep 10
$ echo 3 > /proc/sys/vm/drop_caches | cat /proc/slabinfo | grep dentry
dentry 75145 79002 224 18 1 : tunables 0 0 0 : slabdata 4389 4389 0

$ sleep 10
$ echo 3 > /proc/sys/vm/drop_caches | cat /proc/slabinfo | grep dentry
dentry 75921 79776 224 18 1 : tunables 0 0 0 : slabdata 4432 4432 0
$ git log --pretty=oneline | head -n 2
c83bceb10b36cef895def4b2dfe0aff6ca7c9784 lost path_put in perf_fill_ns_link_info
8b82a8a7ab53ee1a065ac69c835737a701f46b2e Add linux-next specific files for 20171107

Thanks,
Andrei

On Mon, Nov 06, 2017 at 09:22:18AM +0300, Vasily Averin wrote:
> Fixes: commit e422267322cd ("perf: Add PERF_RECORD_NAMESPACES to include namespaces related info")
> Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
> ---
> kernel/events/core.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 10cdb9c..ab5ac84 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -6756,6 +6756,7 @@ static void perf_fill_ns_link_info(struct perf_ns_link_info *ns_link_info,
> ns_inode = ns_path.dentry->d_inode;
> ns_link_info->dev = new_encode_dev(ns_inode->i_sb->s_dev);
> ns_link_info->ino = ns_inode->i_ino;
> + path_put(&ns_path);
> }
> }
>

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