1/* 2 * fs/ioprio.c 3 * 4 * Copyright (C) 2004 Jens Axboe <axboe@kernel.dk> 5 * 6 * Helper functions for setting/querying io priorities of processes. The 7 * system calls closely mimmick getpriority/setpriority, see the man page for 8 * those. The prio argument is a composite of prio class and prio data, where 9 * the data argument has meaning within that class. The standard scheduling 10 * classes have 8 distinct prio levels, with 0 being the highest prio and 7 11 * being the lowest. 12 * 13 * IOW, setting BE scheduling class with prio 2 is done ala: 14 * 15 * unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2; 16 * 17 * ioprio_set(PRIO_PROCESS, pid, prio); 18 * 19 * See also Documentation/block/ioprio.txt 20 * 21 */ 22#include <linux/kernel.h> 23#include <linux/ioprio.h> 24#include <linux/blkdev.h> 25#include <linux/capability.h> 26#include <linux/syscalls.h> 27#include <linux/security.h> 28 29static int set_task_ioprio(struct task_struct *task, int ioprio) 30{ 31 int err; 32 struct io_context *ioc; 33 34 if (task->uid != current->euid && 35 task->uid != current->uid && !capable(CAP_SYS_NICE)) 36 return -EPERM; 37 38 err = security_task_setioprio(task, ioprio); 39 if (err) 40 return err; 41 42 task_lock(task); 43 44 task->ioprio = ioprio; 45 46 ioc = task->io_context; 47 /* see wmb() in current_io_context() */ 48 smp_read_barrier_depends(); 49 50 if (ioc) 51 ioc->ioprio_changed = 1; 52 53 task_unlock(task); 54 return 0; 55} 56 57asmlinkage long sys_ioprio_set(int which, int who, int ioprio) 58{ 59 int class = IOPRIO_PRIO_CLASS(ioprio); 60 int data = IOPRIO_PRIO_DATA(ioprio); 61 struct task_struct *p, *g; 62 struct user_struct *user; 63 struct pid *pgrp; 64 int ret; 65 66 switch (class) { 67 case IOPRIO_CLASS_RT: 68 if (!capable(CAP_SYS_ADMIN)) 69 return -EPERM; 70 /* fall through, rt has prio field too */ 71 case IOPRIO_CLASS_BE: 72 if (data >= IOPRIO_BE_NR || data < 0) 73 return -EINVAL; 74 75 break; 76 case IOPRIO_CLASS_IDLE: 77 if (!capable(CAP_SYS_ADMIN)) 78 return -EPERM; 79 break; 80 default: 81 return -EINVAL; 82 } 83 84 ret = -ESRCH; 85 /* 86 * We want IOPRIO_WHO_PGRP/IOPRIO_WHO_USER to be "atomic", 87 * so we can't use rcu_read_lock(). See re-copy of ->ioprio 88 * in copy_process(). 89 */ 90 read_lock(&tasklist_lock); 91 switch (which) { 92 case IOPRIO_WHO_PROCESS: 93 if (!who) 94 p = current; 95 else 96 p = find_task_by_pid(who); 97 if (p) 98 ret = set_task_ioprio(p, ioprio); 99 break; 100 case IOPRIO_WHO_PGRP: 101 if (!who) 102 pgrp = task_pgrp(current); 103 else 104 pgrp = find_pid(who); 105 do_each_pid_task(pgrp, PIDTYPE_PGID, p) { 106 ret = set_task_ioprio(p, ioprio); 107 if (ret) 108 break; 109 } while_each_pid_task(pgrp, PIDTYPE_PGID, p); 110 break; 111 case IOPRIO_WHO_USER: 112 if (!who) 113 user = current->user; 114 else 115 user = find_user(who); 116 117 if (!user) 118 break; 119 120 do_each_thread(g, p) { 121 if (p->uid != who) 122 continue; 123 ret = set_task_ioprio(p, ioprio); 124 if (ret) 125 goto free_uid; 126 } while_each_thread(g, p); 127free_uid: 128 if (who) 129 free_uid(user); 130 break; 131 default: 132 ret = -EINVAL; 133 } 134 135 read_unlock(&tasklist_lock); 136 return ret; 137} 138 139static int get_task_ioprio(struct task_struct *p) 140{ 141 int ret; 142 143 ret = security_task_getioprio(p); 144 if (ret) 145 goto out; 146 ret = p->ioprio; 147out: 148 return ret; 149} 150 151int ioprio_best(unsigned short aprio, unsigned short bprio) 152{ 153 unsigned short aclass = IOPRIO_PRIO_CLASS(aprio); 154 unsigned short bclass = IOPRIO_PRIO_CLASS(bprio); 155 156 if (aclass == IOPRIO_CLASS_NONE) 157 aclass = IOPRIO_CLASS_BE; 158 if (bclass == IOPRIO_CLASS_NONE) 159 bclass = IOPRIO_CLASS_BE; 160 161 if (aclass == bclass) 162 return min(aprio, bprio); 163 if (aclass > bclass) 164 return bprio; 165 else 166 return aprio; 167} 168 169asmlinkage long sys_ioprio_get(int which, int who) 170{ 171 struct task_struct *g, *p; 172 struct user_struct *user; 173 struct pid *pgrp; 174 int ret = -ESRCH; 175 int tmpio; 176 177 read_lock(&tasklist_lock); 178 switch (which) { 179 case IOPRIO_WHO_PROCESS: 180 if (!who) 181 p = current; 182 else 183 p = find_task_by_pid(who); 184 if (p) 185 ret = get_task_ioprio(p); 186 break; 187 case IOPRIO_WHO_PGRP: 188 if (!who) 189 pgrp = task_pgrp(current); 190 else 191 pgrp = find_pid(who); 192 do_each_pid_task(pgrp, PIDTYPE_PGID, p) { 193 tmpio = get_task_ioprio(p); 194 if (tmpio < 0) 195 continue; 196 if (ret == -ESRCH) 197 ret = tmpio; 198 else 199 ret = ioprio_best(ret, tmpio); 200 } while_each_pid_task(pgrp, PIDTYPE_PGID, p); 201 break; 202 case IOPRIO_WHO_USER: 203 if (!who) 204 user = current->user; 205 else 206 user = find_user(who); 207 208 if (!user) 209 break; 210 211 do_each_thread(g, p) { 212 if (p->uid != user->uid) 213 continue; 214 tmpio = get_task_ioprio(p); 215 if (tmpio < 0) 216 continue; 217 if (ret == -ESRCH) 218 ret = tmpio; 219 else 220 ret = ioprio_best(ret, tmpio); 221 } while_each_thread(g, p); 222 223 if (who) 224 free_uid(user); 225 break; 226 default: 227 ret = -EINVAL; 228 } 229 230 read_unlock(&tasklist_lock); 231 return ret; 232} 233