On Tue, 2017-06-06 at 13:19 -0400, Benjamin Coddington wrote: > Since commit c69899a17ca4 "NFSv4: Update of VFS byte range lock must be > atomic with the stateid update", NFSv4 has been inserting locks in rpciod > worker context. The result is that the file_lock's fl_nspid is the > kworker's pid instead of the original userspace pid. > > The fl_nspid is only used to represent the namespaced virtual pid number > when displaying locks or returning from F_GETLK. There's no reason to set > it for every inserted lock, since we can usually just look it up from > fl_pid. So, instead of looking up and holding struct pid for every lock, > let's just look up the virtual pid number from fl_pid when it is needed. > That means we can remove fl_nspid entirely. >
With this set, I think we ought to codify that the stored pid must be relative > Signed-off-by: Benjamin Coddington <[email protected]> > --- > fs/locks.c | 58 > ++++++++++++++++++++++++++++++++---------------------- > include/linux/fs.h | 1 - > 2 files changed, 35 insertions(+), 24 deletions(-) > > diff --git a/fs/locks.c b/fs/locks.c > index d7daa6c8932f..104398ccc9b9 100644 > --- a/fs/locks.c > +++ b/fs/locks.c > @@ -733,7 +733,6 @@ static void locks_wake_up_blocks(struct file_lock > *blocker) > static void > locks_insert_lock_ctx(struct file_lock *fl, struct list_head *before) > { > - fl->fl_nspid = get_pid(task_tgid(current)); > list_add_tail(&fl->fl_list, before); > locks_insert_global_locks(fl); > } > @@ -743,10 +742,6 @@ locks_unlink_lock_ctx(struct file_lock *fl) > { > locks_delete_global_locks(fl); > list_del_init(&fl->fl_list); > - if (fl->fl_nspid) { > - put_pid(fl->fl_nspid); > - fl->fl_nspid = NULL; > - } > locks_wake_up_blocks(fl); > } > > @@ -823,8 +818,6 @@ posix_test_lock(struct file *filp, struct file_lock *fl) > list_for_each_entry(cfl, &ctx->flc_posix, fl_list) { > if (posix_locks_conflict(fl, cfl)) { > locks_copy_conflock(fl, cfl); > - if (cfl->fl_nspid) > - fl->fl_pid = pid_vnr(cfl->fl_nspid); > goto out; > } > } > @@ -2048,6 +2041,31 @@ int vfs_test_lock(struct file *filp, struct file_lock > *fl) > } > EXPORT_SYMBOL_GPL(vfs_test_lock); > > +/** > + * locks_translate_pid - translate a pid number into a namespace > + * @nr: The pid number in the init_pid_ns > + * @ns: The namespace into which the pid should be translated > + * > + * Used to tranlate a fl_pid into a namespace virtual pid number > + */ > +static pid_t locks_translate_pid(int init_nr, struct pid_namespace *ns) > +{ > + pid_t vnr = 0; > + struct task_struct *task; > + > + rcu_read_lock(); > + task = find_task_by_pid_ns(init_nr, &init_pid_ns); > + if (task) > + get_task_struct(task); > + rcu_read_unlock(); Is that safe? What prevents get_task_struct from doing a 0->1 transition there after the task usage count has already gone 1->0 and is on its way to being freed? > + if (!task) > + goto out; > + vnr = task_pid_nr_ns(task, ns); > + put_task_struct(task); > +out: > + return vnr; > +} > + > static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl) > { > flock->l_pid = IS_OFDLCK(fl) ? -1 : fl->fl_pid; > @@ -2584,22 +2602,16 @@ static void lock_get_status(struct seq_file *f, > struct file_lock *fl, > { > struct inode *inode = NULL; > unsigned int fl_pid; > + struct pid_namespace *proc_pidns = file_inode(f->file)->i_sb->s_fs_info; > > - if (fl->fl_nspid) { > - struct pid_namespace *proc_pidns = > file_inode(f->file)->i_sb->s_fs_info; > - > - /* Don't let fl_pid change based on who is reading the file */ > - fl_pid = pid_nr_ns(fl->fl_nspid, proc_pidns); > - > - /* > - * If there isn't a fl_pid don't display who is waiting on > - * the lock if we are called from locks_show, or if we are > - * called from __show_fd_info - skip lock entirely > - */ > - if (fl_pid == 0) > - return; > - } else > - fl_pid = fl->fl_pid; > + fl_pid = locks_translate_pid(fl->fl_pid, proc_pidns); > + /* > + * If there isn't a fl_pid don't display who is waiting on > + * the lock if we are called from locks_show, or if we are > + * called from __show_fd_info - skip lock entirely > + */ > + if (fl_pid == 0) > + return; > > if (fl->fl_file != NULL) > inode = locks_inode(fl->fl_file); > @@ -2674,7 +2686,7 @@ static int locks_show(struct seq_file *f, void *v) > > fl = hlist_entry(v, struct file_lock, fl_link); > > - if (fl->fl_nspid && !pid_nr_ns(fl->fl_nspid, proc_pidns)) > + if (locks_translate_pid(fl->fl_pid, proc_pidns) == 0) > return 0; > > lock_get_status(f, fl, iter->li_pos, ""); > diff --git a/include/linux/fs.h b/include/linux/fs.h > index aa4affb38c39..b013fac515f7 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -984,7 +984,6 @@ struct file_lock { > unsigned char fl_type; > unsigned int fl_pid; > int fl_link_cpu; /* what cpu's list is this on? */ > - struct pid *fl_nspid; > wait_queue_head_t fl_wait; > struct file *fl_file; > loff_t fl_start; -- Jeff Layton <[email protected]>
