On 25.09.2015 20:56, Oleg Nesterov wrote:
On 09/25, Konstantin Khlebnikov wrote:+struct ns_common *proc_ns_fdget(int fd, int nstype, struct fd *fd_ref) { - struct file *file; + struct ns_common *ns; + struct fd f; - file = fget(fd); - if (!file) + f = fdget(fd); + if (!f.file) return ERR_PTR(-EBADF); - if (file->f_op != &ns_file_operations) + if (f.file->f_op != &ns_file_operations) + goto out_invalid; + + ns = get_proc_ns(file_inode(f.file)); + if (nstype && (ns->ops->type != nstype)) goto out_invalid; - return file; + *fd_ref = f; + return ns; out_invalid: - fput(file); + fdput(f); return ERR_PTR(-EINVAL); }Well yes, fdget() makes sense but this is minor. Honestly, I do not really like the new helper... I understand this is subjective, so I won't insist. But how about 1/1? We do not need fd/file at all. With this patch your sys_getvpid() can just use proc_get_ns_by_fd(fd, CLONE_NEWPID) and put_pid_ns().
Hmm. My version has 0 or 2 atomic ops per get-put sequence. Your version: 2 or 4 atomic ops. Plus even in worst case pinning by struct fd theoretically scales better because it touches refcount at struct file: there're might be many of them for one namespace.
Eric, what do you think? See also "TODO" in the changelog. Oleg.
-- Konstantin -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
