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/gfp.h> 23 #include <linux/kernel.h> 24 #include <linux/export.h> 25 #include <linux/ioprio.h> 26 #include <linux/blkdev.h> 27 #include <linux/capability.h> 28 #include <linux/syscalls.h> 29 #include <linux/security.h> 30 #include <linux/pid_namespace.h> 31 32 int set_task_ioprio(struct task_struct *task, int ioprio) 33 { 34 int err; 35 struct io_context *ioc; 36 const struct cred *cred = current_cred(), *tcred; 37 38 rcu_read_lock(); 39 tcred = __task_cred(task); 40 if (!uid_eq(tcred->uid, cred->euid) && 41 !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) { 42 rcu_read_unlock(); 43 return -EPERM; 44 } 45 rcu_read_unlock(); 46 47 err = security_task_setioprio(task, ioprio); 48 if (err) 49 return err; 50 51 ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE); 52 if (ioc) { 53 ioc->ioprio = ioprio; 54 put_io_context(ioc); 55 } 56 57 return err; 58 } 59 EXPORT_SYMBOL_GPL(set_task_ioprio); 60 61 SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio) 62 { 63 int class = IOPRIO_PRIO_CLASS(ioprio); 64 int data = IOPRIO_PRIO_DATA(ioprio); 65 struct task_struct *p, *g; 66 struct user_struct *user; 67 struct pid *pgrp; 68 kuid_t uid; 69 int ret; 70 71 switch (class) { 72 case IOPRIO_CLASS_RT: 73 if (!capable(CAP_SYS_ADMIN)) 74 return -EPERM; 75 /* fall through, rt has prio field too */ 76 case IOPRIO_CLASS_BE: 77 if (data >= IOPRIO_BE_NR || data < 0) 78 return -EINVAL; 79 80 break; 81 case IOPRIO_CLASS_IDLE: 82 break; 83 case IOPRIO_CLASS_NONE: 84 if (data) 85 return -EINVAL; 86 break; 87 default: 88 return -EINVAL; 89 } 90 91 ret = -ESRCH; 92 rcu_read_lock(); 93 switch (which) { 94 case IOPRIO_WHO_PROCESS: 95 if (!who) 96 p = current; 97 else 98 p = find_task_by_vpid(who); 99 if (p) 100 ret = set_task_ioprio(p, ioprio); 101 break; 102 case IOPRIO_WHO_PGRP: 103 if (!who) 104 pgrp = task_pgrp(current); 105 else 106 pgrp = find_vpid(who); 107 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { 108 ret = set_task_ioprio(p, ioprio); 109 if (ret) 110 break; 111 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); 112 break; 113 case IOPRIO_WHO_USER: 114 uid = make_kuid(current_user_ns(), who); 115 if (!uid_valid(uid)) 116 break; 117 if (!who) 118 user = current_user(); 119 else 120 user = find_user(uid); 121 122 if (!user) 123 break; 124 125 do_each_thread(g, p) { 126 if (!uid_eq(task_uid(p), uid)) 127 continue; 128 ret = set_task_ioprio(p, ioprio); 129 if (ret) 130 goto free_uid; 131 } while_each_thread(g, p); 132 free_uid: 133 if (who) 134 free_uid(user); 135 break; 136 default: 137 ret = -EINVAL; 138 } 139 140 rcu_read_unlock(); 141 return ret; 142 } 143 144 static int get_task_ioprio(struct task_struct *p) 145 { 146 int ret; 147 148 ret = security_task_getioprio(p); 149 if (ret) 150 goto out; 151 ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM); 152 if (p->io_context) 153 ret = p->io_context->ioprio; 154 out: 155 return ret; 156 } 157 158 int ioprio_best(unsigned short aprio, unsigned short bprio) 159 { 160 unsigned short aclass; 161 unsigned short bclass; 162 163 if (!ioprio_valid(aprio)) 164 aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM); 165 if (!ioprio_valid(bprio)) 166 bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM); 167 168 aclass = IOPRIO_PRIO_CLASS(aprio); 169 bclass = IOPRIO_PRIO_CLASS(bprio); 170 if (aclass == bclass) 171 return min(aprio, bprio); 172 if (aclass > bclass) 173 return bprio; 174 else 175 return aprio; 176 } 177 178 SYSCALL_DEFINE2(ioprio_get, int, which, int, who) 179 { 180 struct task_struct *g, *p; 181 struct user_struct *user; 182 struct pid *pgrp; 183 kuid_t uid; 184 int ret = -ESRCH; 185 int tmpio; 186 187 rcu_read_lock(); 188 switch (which) { 189 case IOPRIO_WHO_PROCESS: 190 if (!who) 191 p = current; 192 else 193 p = find_task_by_vpid(who); 194 if (p) 195 ret = get_task_ioprio(p); 196 break; 197 case IOPRIO_WHO_PGRP: 198 if (!who) 199 pgrp = task_pgrp(current); 200 else 201 pgrp = find_vpid(who); 202 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { 203 tmpio = get_task_ioprio(p); 204 if (tmpio < 0) 205 continue; 206 if (ret == -ESRCH) 207 ret = tmpio; 208 else 209 ret = ioprio_best(ret, tmpio); 210 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); 211 break; 212 case IOPRIO_WHO_USER: 213 uid = make_kuid(current_user_ns(), who); 214 if (!who) 215 user = current_user(); 216 else 217 user = find_user(uid); 218 219 if (!user) 220 break; 221 222 do_each_thread(g, p) { 223 if (!uid_eq(task_uid(p), user->uid)) 224 continue; 225 tmpio = get_task_ioprio(p); 226 if (tmpio < 0) 227 continue; 228 if (ret == -ESRCH) 229 ret = tmpio; 230 else 231 ret = ioprio_best(ret, tmpio); 232 } while_each_thread(g, p); 233 234 if (who) 235 free_uid(user); 236 break; 237 default: 238 ret = -EINVAL; 239 } 240 241 rcu_read_unlock(); 242 return ret; 243 } 244