Re: [PATCH 0/2] fs/lock: show locks info owned by dead/invisible processes

[Konstantin Khorenko]

On 08/09/2018 10:16 AM, Murphy Zhou wrote:
> Hi,
>
> Looks like this missed v4.18 ?

Hi Murphy,

yes, Jeff planned to push those patches into 4.19 and they are in "linux-next" now,
but not in 4.18 "master" currently.

On 06/14/2018 01:41 PM, Jeff Layton wrote:
> These look fine to me. I'll plan to pick them up for v4.19 unless anyone
> has objections.

linux-next:
1cf8e5de4055 ("fs/lock: show locks taken by processes from another pidns")
826d7bc9f013 ("fs/lock: skip lock owner pid translation in case we are in init_pid_ns")

--
Best regards,

Konstantin Khorenko,
Virtuozzo Linux Kernel Team

> On Fri, Jun 8, 2018 at 10:27 PM, Konstantin Khorenko
> <khorenko@xxxxxxxxxxxxx> wrote:
> > The behavior has been changed after 9d5b86ac13c5 ("fs/locks: Remove fl_nspid
> > and use fs-specific l_pid for remote locks")
> > and now /proc/$PID/fdinfo/$FD does not show the info about the lock
> > * if the flock owner process is dead and its pid has been already freed
> > or
> > * if the lock owner is not visible in current pidns.
> >
> > CRIU uses this interface to store locks info during dump and thus can break
> > on v4.13 and newer.
> >
> > So let's show info about locks anyway in described cases (like it was before
> > 9d5b86ac13c5), but show pid number saved in file_lock struct if we are in
> > init_pid_ns (patch 1) or just zero otherwise (patch 2) like we do with SID.
> >
> > Reproducer:
> > process A       process A1      process A2
> > fork()--------->
> > exit()          open()
> >                 flock()
> >                 fork()--------->
> >                 exit()          sleep()
> >
> > Before the patch:
> > ================
> > (root@vz7)/: cat /proc/${PID_A2}/fdinfo/3
> > pos:    4
> > flags:  02100002
> > mnt_id: 257
> > lock:   (root@vz7)/:
> >
> > After the patch:
> > ===============
> > (root@vz7)/:cat /proc/${PID_A2}/fdinfo/3
> > pos:    4
> > flags:  02100002
> > mnt_id: 295
> > lock:   1: FLOCK  ADVISORY  WRITE ${PID_A1} b6:f8a61:529946 0 EOF
> >
> > ===============
> > # cat flock1.c
> >
> > #include <stdio.h>
> > #include <stdlib.h>
> > #include <unistd.h>
> > #include <sys/types.h>
> > #include <sys/stat.h>
> > #include <sys/file.h>
> > #include <fcntl.h>
> >
> > int main(void)
> > {
> >         int fd;
> >         int err;
> >         pid_t child_pid;
> >
> >         child_pid = fork();
> >         if (child_pid == -1)
> >                 perror("fork failed");
> >         if (child_pid) {
> >                 exit(0);
> >         }
> >
> >         fd = open("/tmp/a", O_CREAT | O_RDWR);
> >         if (fd == -1)
> >                 perror("Failed to open the file");
> >
> >         err = flock(fd, LOCK_EX);
> >         if (err == -1)
> >                 perror("flock failed");
> >
> >         child_pid = fork();
> >         if (child_pid == -1)
> >                 perror("fork failed");
> >         if (child_pid)
> >                 exit(0);
> >
> >         sleep(10000);
> >
> >         return 0;
> > }
> >
> > Konstantin Khorenko (2):
> >   fs/lock: skip lock owner pid translation in case we are in init_pid_ns
> >   fs/lock: show locks taken by processes from another pidns
> >
> >  fs/locks.c | 15 ++++++++++-----
> >  1 file changed, 10 insertions(+), 5 deletions(-)
> >
> > --
> > 2.15.1
> .