/* * fs/ioprio.c * * Copyright (C) 2004 Jens Axboe <axboe@kernel.dk> * * Helper functions for setting/querying io priorities of processes. The * system calls closely mimmick getpriority/setpriority, see the man page for * those. The prio argument is a composite of prio class and prio data, where * the data argument has meaning within that class. The standard scheduling * classes have 8 distinct prio levels, with 0 being the highest prio and 7 * being the lowest. * * IOW, setting BE scheduling class with prio 2 is done ala: * * unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2; * * ioprio_set(PRIO_PROCESS, pid, prio); * * See also Documentation/block/ioprio.txt * */ #include <linux/kernel.h> #include <linux/ioprio.h> #include <linux/blkdev.h> #include <linux/capability.h> #include <linux/syscalls.h> #include <linux/security.h> static int set_task_ioprio(struct task_struct *task, int ioprio) { int err; struct io_context *ioc; if (task->uid != current->euid && task->uid != current->uid && !capable(CAP_SYS_NICE)) return -EPERM; err = security_task_setioprio(task, ioprio); if (err) return err; task_lock(task); task->ioprio = ioprio; ioc = task->io_context; /* see wmb() in current_io_context() */ smp_read_barrier_depends(); if (ioc) ioc->ioprio_changed = 1; task_unlock(task); return 0; } asmlinkage long sys_ioprio_set(int which, int who, int ioprio) { int class = IOPRIO_PRIO_CLASS(ioprio); int data = IOPRIO_PRIO_DATA(ioprio); struct task_struct *p, *g; struct user_struct *user; int ret; switch (class) { case IOPRIO_CLASS_RT: if (!capable(CAP_SYS_ADMIN)) return -EPERM; /* fall through, rt has prio field too */ case IOPRIO_CLASS_BE: if (data >= IOPRIO_BE_NR || data < 0) return -EINVAL; break; case IOPRIO_CLASS_IDLE: if (!capable(CAP_SYS_ADMIN)) return -EPERM; break; default: return -EINVAL; } ret = -ESRCH; /* * We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic", * so we can't use rcu_read_lock(). See re-copy of ->ioprio * in copy_process(). */ read_lock(&tasklist_lock); switch (which) { case IOPRIO_WHO_PROCESS: if (!who) p = current; else p = find_task_by_pid(who); if (p) ret = set_task_ioprio(p, ioprio); break; case IOPRIO_WHO_PGRP: if (!who) who = process_group(current); do_each_task_pid(who, PIDTYPE_PGID, p) { ret = set_task_ioprio(p, ioprio); if (ret) break; } while_each_task_pid(who, PIDTYPE_PGID, p); break; case IOPRIO_WHO_USER: if (!who) user = current->user; else user = find_user(who); if (!user) break; do_each_thread(g, p) { if (p->uid != who) continue; ret = set_task_ioprio(p, ioprio); if (ret) goto free_uid; } while_each_thread(g, p); free_uid: if (who) free_uid(user); break; default: ret = -EINVAL; } read_unlock(&tasklist_lock); return ret; } static int get_task_ioprio(struct task_struct *p) { int ret; ret = security_task_getioprio(p); if (ret) goto out; ret = p->ioprio; out: return ret; } int ioprio_best(unsigned short aprio, unsigned short bprio) { unsigned short aclass = IOPRIO_PRIO_CLASS(aprio); unsigned short bclass = IOPRIO_PRIO_CLASS(bprio); if (!ioprio_valid(aprio)) return bprio; if (!ioprio_valid(bprio)) return aprio; if (aclass == IOPRIO_CLASS_NONE) aclass = IOPRIO_CLASS_BE; if (bclass == IOPRIO_CLASS_NONE) bclass = IOPRIO_CLASS_BE; if (aclass == bclass) return min(aprio, bprio); if (aclass > bclass) return bprio; else return aprio; } asmlinkage long sys_ioprio_get(int which, int who) { struct task_struct *g, *p; struct user_struct *user; int ret = -ESRCH; int tmpio; read_lock(&tasklist_lock); switch (which) { case IOPRIO_WHO_PROCESS: if (!who) p = current; else p = find_task_by_pid(who); if (p) ret = get_task_ioprio(p); break; case IOPRIO_WHO_PGRP: if (!who) who = process_group(current); do_each_task_pid(who, PIDTYPE_PGID, p) { tmpio = get_task_ioprio(p); if (tmpio < 0) continue; if (ret == -ESRCH) ret = tmpio; else ret = ioprio_best(ret, tmpio); } while_each_task_pid(who, PIDTYPE_PGID, p); break; case IOPRIO_WHO_USER: if (!who) user = current->user; else user = find_user(who); if (!user) break; do_each_thread(g, p) { if (p->uid != user->uid) continue; tmpio = get_task_ioprio(p); if (tmpio < 0) continue; if (ret == -ESRCH) ret = tmpio; else ret = ioprio_best(ret, tmpio); } while_each_thread(g, p); if (who) free_uid(user); break; default: ret = -EINVAL; } read_unlock(&tasklist_lock); return ret; }