1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * fs/ioprio.c 4 * 5 * Copyright (C) 2004 Jens Axboe <axboe@kernel.dk> 6 * 7 * Helper functions for setting/querying io priorities of processes. The 8 * system calls closely mimmick getpriority/setpriority, see the man page for 9 * those. The prio argument is a composite of prio class and prio data, where 10 * the data argument has meaning within that class. The standard scheduling 11 * classes have 8 distinct prio levels, with 0 being the highest prio and 7 12 * being the lowest. 13 * 14 * IOW, setting BE scheduling class with prio 2 is done ala: 15 * 16 * unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2; 17 * 18 * ioprio_set(PRIO_PROCESS, pid, prio); 19 * 20 * See also Documentation/block/ioprio.rst 21 * 22 */ 23 #include <linux/gfp.h> 24 #include <linux/kernel.h> 25 #include <linux/export.h> 26 #include <linux/ioprio.h> 27 #include <linux/cred.h> 28 #include <linux/blkdev.h> 29 #include <linux/capability.h> 30 #include <linux/sched/user.h> 31 #include <linux/sched/task.h> 32 #include <linux/syscalls.h> 33 #include <linux/security.h> 34 #include <linux/pid_namespace.h> 35 36 int set_task_ioprio(struct task_struct *task, int ioprio) 37 { 38 int err; 39 struct io_context *ioc; 40 const struct cred *cred = current_cred(), *tcred; 41 42 rcu_read_lock(); 43 tcred = __task_cred(task); 44 if (!uid_eq(tcred->uid, cred->euid) && 45 !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) { 46 rcu_read_unlock(); 47 return -EPERM; 48 } 49 rcu_read_unlock(); 50 51 err = security_task_setioprio(task, ioprio); 52 if (err) 53 return err; 54 55 ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE); 56 if (ioc) { 57 ioc->ioprio = ioprio; 58 put_io_context(ioc); 59 } 60 61 return err; 62 } 63 EXPORT_SYMBOL_GPL(set_task_ioprio); 64 65 int ioprio_check_cap(int ioprio) 66 { 67 int class = IOPRIO_PRIO_CLASS(ioprio); 68 int data = IOPRIO_PRIO_DATA(ioprio); 69 70 switch (class) { 71 case IOPRIO_CLASS_RT: 72 if (!capable(CAP_SYS_ADMIN)) 73 return -EPERM; 74 fallthrough; 75 /* 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 return 0; 92 } 93 94 SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio) 95 { 96 struct task_struct *p, *g; 97 struct user_struct *user; 98 struct pid *pgrp; 99 kuid_t uid; 100 int ret; 101 102 ret = ioprio_check_cap(ioprio); 103 if (ret) 104 return ret; 105 106 ret = -ESRCH; 107 rcu_read_lock(); 108 switch (which) { 109 case IOPRIO_WHO_PROCESS: 110 if (!who) 111 p = current; 112 else 113 p = find_task_by_vpid(who); 114 if (p) 115 ret = set_task_ioprio(p, ioprio); 116 break; 117 case IOPRIO_WHO_PGRP: 118 if (!who) 119 pgrp = task_pgrp(current); 120 else 121 pgrp = find_vpid(who); 122 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { 123 ret = set_task_ioprio(p, ioprio); 124 if (ret) 125 break; 126 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); 127 break; 128 case IOPRIO_WHO_USER: 129 uid = make_kuid(current_user_ns(), who); 130 if (!uid_valid(uid)) 131 break; 132 if (!who) 133 user = current_user(); 134 else 135 user = find_user(uid); 136 137 if (!user) 138 break; 139 140 for_each_process_thread(g, p) { 141 if (!uid_eq(task_uid(p), uid) || 142 !task_pid_vnr(p)) 143 continue; 144 ret = set_task_ioprio(p, ioprio); 145 if (ret) 146 goto free_uid; 147 } 148 free_uid: 149 if (who) 150 free_uid(user); 151 break; 152 default: 153 ret = -EINVAL; 154 } 155 156 rcu_read_unlock(); 157 return ret; 158 } 159 160 static int get_task_ioprio(struct task_struct *p) 161 { 162 int ret; 163 164 ret = security_task_getioprio(p); 165 if (ret) 166 goto out; 167 ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM); 168 task_lock(p); 169 if (p->io_context) 170 ret = p->io_context->ioprio; 171 task_unlock(p); 172 out: 173 return ret; 174 } 175 176 int ioprio_best(unsigned short aprio, unsigned short bprio) 177 { 178 if (!ioprio_valid(aprio)) 179 aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM); 180 if (!ioprio_valid(bprio)) 181 bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM); 182 183 return min(aprio, bprio); 184 } 185 186 SYSCALL_DEFINE2(ioprio_get, int, which, int, who) 187 { 188 struct task_struct *g, *p; 189 struct user_struct *user; 190 struct pid *pgrp; 191 kuid_t uid; 192 int ret = -ESRCH; 193 int tmpio; 194 195 rcu_read_lock(); 196 switch (which) { 197 case IOPRIO_WHO_PROCESS: 198 if (!who) 199 p = current; 200 else 201 p = find_task_by_vpid(who); 202 if (p) 203 ret = get_task_ioprio(p); 204 break; 205 case IOPRIO_WHO_PGRP: 206 if (!who) 207 pgrp = task_pgrp(current); 208 else 209 pgrp = find_vpid(who); 210 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { 211 tmpio = get_task_ioprio(p); 212 if (tmpio < 0) 213 continue; 214 if (ret == -ESRCH) 215 ret = tmpio; 216 else 217 ret = ioprio_best(ret, tmpio); 218 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); 219 break; 220 case IOPRIO_WHO_USER: 221 uid = make_kuid(current_user_ns(), who); 222 if (!who) 223 user = current_user(); 224 else 225 user = find_user(uid); 226 227 if (!user) 228 break; 229 230 for_each_process_thread(g, p) { 231 if (!uid_eq(task_uid(p), user->uid) || 232 !task_pid_vnr(p)) 233 continue; 234 tmpio = get_task_ioprio(p); 235 if (tmpio < 0) 236 continue; 237 if (ret == -ESRCH) 238 ret = tmpio; 239 else 240 ret = ioprio_best(ret, tmpio); 241 } 242 243 if (who) 244 free_uid(user); 245 break; 246 default: 247 ret = -EINVAL; 248 } 249 250 rcu_read_unlock(); 251 return ret; 252 } 253