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 !task_pid_vnr(p)) 128 continue; 129 ret = set_task_ioprio(p, ioprio); 130 if (ret) 131 goto free_uid; 132 } while_each_thread(g, p); 133 free_uid: 134 if (who) 135 free_uid(user); 136 break; 137 default: 138 ret = -EINVAL; 139 } 140 141 rcu_read_unlock(); 142 return ret; 143 } 144 145 static int get_task_ioprio(struct task_struct *p) 146 { 147 int ret; 148 149 ret = security_task_getioprio(p); 150 if (ret) 151 goto out; 152 ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM); 153 task_lock(p); 154 if (p->io_context) 155 ret = p->io_context->ioprio; 156 task_unlock(p); 157 out: 158 return ret; 159 } 160 161 int ioprio_best(unsigned short aprio, unsigned short bprio) 162 { 163 unsigned short aclass; 164 unsigned short bclass; 165 166 if (!ioprio_valid(aprio)) 167 aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM); 168 if (!ioprio_valid(bprio)) 169 bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM); 170 171 aclass = IOPRIO_PRIO_CLASS(aprio); 172 bclass = IOPRIO_PRIO_CLASS(bprio); 173 if (aclass == bclass) 174 return min(aprio, bprio); 175 if (aclass > bclass) 176 return bprio; 177 else 178 return aprio; 179 } 180 181 SYSCALL_DEFINE2(ioprio_get, int, which, int, who) 182 { 183 struct task_struct *g, *p; 184 struct user_struct *user; 185 struct pid *pgrp; 186 kuid_t uid; 187 int ret = -ESRCH; 188 int tmpio; 189 190 rcu_read_lock(); 191 switch (which) { 192 case IOPRIO_WHO_PROCESS: 193 if (!who) 194 p = current; 195 else 196 p = find_task_by_vpid(who); 197 if (p) 198 ret = get_task_ioprio(p); 199 break; 200 case IOPRIO_WHO_PGRP: 201 if (!who) 202 pgrp = task_pgrp(current); 203 else 204 pgrp = find_vpid(who); 205 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { 206 tmpio = get_task_ioprio(p); 207 if (tmpio < 0) 208 continue; 209 if (ret == -ESRCH) 210 ret = tmpio; 211 else 212 ret = ioprio_best(ret, tmpio); 213 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); 214 break; 215 case IOPRIO_WHO_USER: 216 uid = make_kuid(current_user_ns(), who); 217 if (!who) 218 user = current_user(); 219 else 220 user = find_user(uid); 221 222 if (!user) 223 break; 224 225 do_each_thread(g, p) { 226 if (!uid_eq(task_uid(p), user->uid) || 227 !task_pid_vnr(p)) 228 continue; 229 tmpio = get_task_ioprio(p); 230 if (tmpio < 0) 231 continue; 232 if (ret == -ESRCH) 233 ret = tmpio; 234 else 235 ret = ioprio_best(ret, tmpio); 236 } while_each_thread(g, p); 237 238 if (who) 239 free_uid(user); 240 break; 241 default: 242 ret = -EINVAL; 243 } 244 245 rcu_read_unlock(); 246 return ret; 247 } 248