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/cred.h> 27 #include <linux/blkdev.h> 28 #include <linux/capability.h> 29 #include <linux/sched/user.h> 30 #include <linux/sched/task.h> 31 #include <linux/syscalls.h> 32 #include <linux/security.h> 33 #include <linux/pid_namespace.h> 34 35 int set_task_ioprio(struct task_struct *task, int ioprio) 36 { 37 int err; 38 struct io_context *ioc; 39 const struct cred *cred = current_cred(), *tcred; 40 41 rcu_read_lock(); 42 tcred = __task_cred(task); 43 if (!uid_eq(tcred->uid, cred->euid) && 44 !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) { 45 rcu_read_unlock(); 46 return -EPERM; 47 } 48 rcu_read_unlock(); 49 50 err = security_task_setioprio(task, ioprio); 51 if (err) 52 return err; 53 54 ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE); 55 if (ioc) { 56 ioc->ioprio = ioprio; 57 put_io_context(ioc); 58 } 59 60 return err; 61 } 62 EXPORT_SYMBOL_GPL(set_task_ioprio); 63 64 int ioprio_check_cap(int ioprio) 65 { 66 int class = IOPRIO_PRIO_CLASS(ioprio); 67 int data = IOPRIO_PRIO_DATA(ioprio); 68 69 switch (class) { 70 case IOPRIO_CLASS_RT: 71 if (!capable(CAP_SYS_ADMIN)) 72 return -EPERM; 73 /* fall through */ 74 /* rt has prio field too */ 75 case IOPRIO_CLASS_BE: 76 if (data >= IOPRIO_BE_NR || data < 0) 77 return -EINVAL; 78 79 break; 80 case IOPRIO_CLASS_IDLE: 81 break; 82 case IOPRIO_CLASS_NONE: 83 if (data) 84 return -EINVAL; 85 break; 86 default: 87 return -EINVAL; 88 } 89 90 return 0; 91 } 92 93 SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio) 94 { 95 struct task_struct *p, *g; 96 struct user_struct *user; 97 struct pid *pgrp; 98 kuid_t uid; 99 int ret; 100 101 ret = ioprio_check_cap(ioprio); 102 if (ret) 103 return ret; 104 105 ret = -ESRCH; 106 rcu_read_lock(); 107 switch (which) { 108 case IOPRIO_WHO_PROCESS: 109 if (!who) 110 p = current; 111 else 112 p = find_task_by_vpid(who); 113 if (p) 114 ret = set_task_ioprio(p, ioprio); 115 break; 116 case IOPRIO_WHO_PGRP: 117 if (!who) 118 pgrp = task_pgrp(current); 119 else 120 pgrp = find_vpid(who); 121 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { 122 ret = set_task_ioprio(p, ioprio); 123 if (ret) 124 break; 125 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); 126 break; 127 case IOPRIO_WHO_USER: 128 uid = make_kuid(current_user_ns(), who); 129 if (!uid_valid(uid)) 130 break; 131 if (!who) 132 user = current_user(); 133 else 134 user = find_user(uid); 135 136 if (!user) 137 break; 138 139 for_each_process_thread(g, p) { 140 if (!uid_eq(task_uid(p), uid) || 141 !task_pid_vnr(p)) 142 continue; 143 ret = set_task_ioprio(p, ioprio); 144 if (ret) 145 goto free_uid; 146 } 147 free_uid: 148 if (who) 149 free_uid(user); 150 break; 151 default: 152 ret = -EINVAL; 153 } 154 155 rcu_read_unlock(); 156 return ret; 157 } 158 159 static int get_task_ioprio(struct task_struct *p) 160 { 161 int ret; 162 163 ret = security_task_getioprio(p); 164 if (ret) 165 goto out; 166 ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM); 167 task_lock(p); 168 if (p->io_context) 169 ret = p->io_context->ioprio; 170 task_unlock(p); 171 out: 172 return ret; 173 } 174 175 int ioprio_best(unsigned short aprio, unsigned short bprio) 176 { 177 if (!ioprio_valid(aprio)) 178 aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM); 179 if (!ioprio_valid(bprio)) 180 bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM); 181 182 return min(aprio, bprio); 183 } 184 185 SYSCALL_DEFINE2(ioprio_get, int, which, int, who) 186 { 187 struct task_struct *g, *p; 188 struct user_struct *user; 189 struct pid *pgrp; 190 kuid_t uid; 191 int ret = -ESRCH; 192 int tmpio; 193 194 rcu_read_lock(); 195 switch (which) { 196 case IOPRIO_WHO_PROCESS: 197 if (!who) 198 p = current; 199 else 200 p = find_task_by_vpid(who); 201 if (p) 202 ret = get_task_ioprio(p); 203 break; 204 case IOPRIO_WHO_PGRP: 205 if (!who) 206 pgrp = task_pgrp(current); 207 else 208 pgrp = find_vpid(who); 209 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { 210 tmpio = get_task_ioprio(p); 211 if (tmpio < 0) 212 continue; 213 if (ret == -ESRCH) 214 ret = tmpio; 215 else 216 ret = ioprio_best(ret, tmpio); 217 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); 218 break; 219 case IOPRIO_WHO_USER: 220 uid = make_kuid(current_user_ns(), who); 221 if (!who) 222 user = current_user(); 223 else 224 user = find_user(uid); 225 226 if (!user) 227 break; 228 229 for_each_process_thread(g, p) { 230 if (!uid_eq(task_uid(p), user->uid) || 231 !task_pid_vnr(p)) 232 continue; 233 tmpio = get_task_ioprio(p); 234 if (tmpio < 0) 235 continue; 236 if (ret == -ESRCH) 237 ret = tmpio; 238 else 239 ret = ioprio_best(ret, tmpio); 240 } 241 242 if (who) 243 free_uid(user); 244 break; 245 default: 246 ret = -EINVAL; 247 } 248 249 rcu_read_unlock(); 250 return ret; 251 } 252