/* * 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> #include <linux/pid_namespace.h> int set_task_ioprio(struct task_struct *task, int ioprio) { int err; struct io_context *ioc; const struct cred *cred = current_cred(), *tcred; rcu_read_lock(); tcred = __task_cred(task); if (tcred->uid != cred->euid && tcred->uid != cred->uid && !capable(CAP_SYS_NICE)) { rcu_read_unlock(); return -EPERM; } rcu_read_unlock(); err = security_task_setioprio(task, ioprio); if (err) return err; task_lock(task); do { ioc = task->io_context; /* see wmb() in current_io_context() */ smp_read_barrier_depends(); if (ioc) break; ioc = alloc_io_context(GFP_ATOMIC, -1); if (!ioc) { err = -ENOMEM; break; } task->io_context = ioc; } while (1); if (!err) { ioc->ioprio = ioprio; ioc->ioprio_changed = 1; } task_unlock(task); return err; } EXPORT_SYMBOL_GPL(set_task_ioprio); SYSCALL_DEFINE3(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; struct pid *pgrp; 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: break; case IOPRIO_CLASS_NONE: if (data) return -EINVAL; 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_vpid(who); if (p) ret = set_task_ioprio(p, ioprio); break; case IOPRIO_WHO_PGRP: if (!who) pgrp = task_pgrp(current); else pgrp = find_vpid(who); do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { ret = set_task_ioprio(p, ioprio); if (ret) break; } while_each_pid_thread(pgrp, 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 (__task_cred(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 = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM); if (p->io_context) ret = p->io_context->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 (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; } SYSCALL_DEFINE2(ioprio_get, int, which, int, who) { struct task_struct *g, *p; struct user_struct *user; struct pid *pgrp; int ret = -ESRCH; int tmpio; read_lock(&tasklist_lock); switch (which) { case IOPRIO_WHO_PROCESS: if (!who) p = current; else p = find_task_by_vpid(who); if (p) ret = get_task_ioprio(p); break; case IOPRIO_WHO_PGRP: if (!who) pgrp = task_pgrp(current); else pgrp = find_vpid(who); do_each_pid_thread(pgrp, 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_pid_thread(pgrp, 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 (__task_cred(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; }