On Wed, Oct 21, 2009 at 7:11 PM, Corentin Chary <corentin.chary@xxxxxxxxx> wrote: > On Wed, Oct 21, 2009 at 3:16 PM, Corentin Chary > <corentin.chary@xxxxxxxxx> wrote: >> First, some background: >> - getpid() returns current->tgid which is the pid of the first thread >> - gettid() returns current->pid which is the pid of the current thread >> For all threads, getpid() is the same. >> >> From fuse.h : >>> For F_SETLK and F_SETLKW the l_pid field will be set to the pid >>> of the process performing the locking operation. >> Short: l_pid will always be equal to tgid >> >>> struct fuse_context >>> /** Thread ID of the calling process */ >>> pid_t pid; >> Short: ctx->pid will always be thread id (current->pid / gettid()) >> >> posix_locks use this pid in same_owner(), but pl_forget will be called >> with the pid (current->pid) from the thread who did the close. Locks >> granted to other threads, won't be deleted. >> >> This can also affect some other translators. >> >> GlusterFS don't want the Thread ID (current->pid), it needs the Process ID >> (current->tgid), at least for >> >> A quick hack to make it work with thread would be to getpgid(ctx->pid), >> but this won't work in a lot of case (for example, daemonized process). >> >> You may also want to use the l_pid field in struct flock, but this >> won't work because you don't know who will close >> the fd and call pl_flush. >> >> Another way is to add a syscall to get the tgid from the pid, but I >> don't think this will happens. >> >> The easiest way is to add a tgid field in fuse in order to use >> ctx->tgid instead of ctx->pid. >> >> Finally, a quick&dirty fix can be made reading /proc/<ctx->pid>/status >> in order to find the Tgid: line. >> >> -- >> Corentin Chary >> http://xf.iksaif.net >> > > Reading the fuse source, I found the solution: > fuse_file_info->lock_owner should be used to check ownership instead of pid. > This way the pid/tgid thing is no more an issue. > Patch comming tomorow =) Reading more glusterfs code lead me to this conclusion: - lock_owner can be used for fuse, but to use that we need to add lock_owner to _call_stack_t or add lock_owner to gf_flock and use it everywhere instead of struct flock. For libglusterfs_client and booster we can probably use getpid() to fill lock_owner. - glusterfs fs *need* the tgid for fd_create/fd_lookup So, patch not comming tomorow, because I'm not sure what's the best way to fix that. -- Corentin Chary http://xf.iksaif.net
