Hi!,

On 02/06/2015 02:44 PM, John Spray wrote:
> You should let the caller pass in the owner ID.  For example, if you
> were using libcephfs to implement a filesystem interface, it would be
> up to that interface to work out the unique ID from the calling layer
> above it.  So you can pass it through libcephfs, no logic needed.

Thanks. I assume the locking depends on the (pid, owner) tuple in this case ?

>> Thanks in advance for any hints! By the way - would this new feature (flock()) make sense ?
> Definitely, the flock support in the userspace client is new, and the
> libcephfs bindings just didn't catch up yet: it was added in October:

Not sure if my patch looks sane enough to be submitted, but here it is. Please advise me if there is a more suitable way than posting patches here :)

[ Note that I did not ran extensive tests now, but this is only an interface to the existing Client interface one, and the very minimalistic test sample below seems to be working fine.
]

////////// Sample test //////////
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <cephfs/libcephfs.h>

static bool check(const char *name, int code) {
  if (code >= 0) {
    fprintf(stderr, "%s: OK\n", name);
    return true;
  } else {
    errno = -code;
    perror(name);
    fprintf(stderr, "%s: ERROR\n", name);
    return false;
  }
}

int main(int argc, char **argv) {
  int success = EXIT_FAILURE;
  struct ceph_mount_info *cmount = NULL;

  int fd;
  if (check("ceph_create", ceph_create(&cmount, "admin"))
      && check("ceph_conf_set(keyfile)",
               ceph_conf_set(cmount, "keyfile",
                             "ceph.admin.key"))
      && check("ceph_conf_set(mon_host)",
               ceph_conf_set(cmount, "mon_host", "10.42.42.42"))
      && check("ceph_conf_set(log_to_stderr)",
               ceph_conf_set(cmount, "log_to_stderr", "true"))
      && check("ceph_mount", ceph_mount(cmount, NULL))
      && check("ceph_open",
               fd = ceph_open(cmount, "/test.lock", O_RDWR | O_CREAT,
                              S_IRWXU | S_IRWXG | S_IRWXO))
      ) {
    if (check("ceph_flock", ceph_flock(cmount, fd, LOCK_EX, 42))) {
      success = EXIT_SUCCESS;
    }
    
    fd >= 0 && check("ceph_close", ceph_close(cmount, fd));
  }
  cmount != NULL && check("ceph_unmount", ceph_unmount(cmount));

  return success;
}