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 SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio) 65 { 66 int class = IOPRIO_PRIO_CLASS(ioprio); 67 int data = IOPRIO_PRIO_DATA(ioprio); 68 struct task_struct *p, *g; 69 struct user_struct *user; 70 struct pid *pgrp; 71 kuid_t uid; 72 int ret; 73 74 switch (class) { 75 case IOPRIO_CLASS_RT: 76 if (!capable(CAP_SYS_ADMIN)) 77 return -EPERM; 78 /* fall through */ 79 /* rt has prio field too */ 80 case IOPRIO_CLASS_BE: 81 if (data >= IOPRIO_BE_NR || data < 0) 82 return -EINVAL; 83 84 break; 85 case IOPRIO_CLASS_IDLE: 86 break; 87 case IOPRIO_CLASS_NONE: 88 if (data) 89 return -EINVAL; 90 break; 91 default: 92 return -EINVAL; 93 } 94 95 ret = -ESRCH; 96 rcu_read_lock(); 97 switch (which) { 98 case IOPRIO_WHO_PROCESS: 99 if (!who) 100 p = current; 101 else 102 p = find_task_by_vpid(who); 103 if (p) 104 ret = set_task_ioprio(p, ioprio); 105 break; 106 case IOPRIO_WHO_PGRP: 107 if (!who) 108 pgrp = task_pgrp(current); 109 else 110 pgrp = find_vpid(who); 111 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { 112 ret = set_task_ioprio(p, ioprio); 113 if (ret) 114 break; 115 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); 116 break; 117 case IOPRIO_WHO_USER: 118 uid = make_kuid(current_user_ns(), who); 119 if (!uid_valid(uid)) 120 break; 121 if (!who) 122 user = current_user(); 123 else 124 user = find_user(uid); 125 126 if (!user) 127 break; 128 129 for_each_process_thread(g, p) { 130 if (!uid_eq(task_uid(p), uid) || 131 !task_pid_vnr(p)) 132 continue; 133 ret = set_task_ioprio(p, ioprio); 134 if (ret) 135 goto free_uid; 136 } 137 free_uid: 138 if (who) 139 free_uid(user); 140 break; 141 default: 142 ret = -EINVAL; 143 } 144 145 rcu_read_unlock(); 146 return ret; 147 } 148 149 static int get_task_ioprio(struct task_struct *p) 150 { 151 int ret; 152 153 ret = security_task_getioprio(p); 154 if (ret) 155 goto out; 156 ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM); 157 task_lock(p); 158 if (p->io_context) 159 ret = p->io_context->ioprio; 160 task_unlock(p); 161 out: 162 return ret; 163 } 164 165 int ioprio_best(unsigned short aprio, unsigned short bprio) 166 { 167 if (!ioprio_valid(aprio)) 168 aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM); 169 if (!ioprio_valid(bprio)) 170 bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM); 171 172 return min(aprio, bprio); 173 } 174 175 SYSCALL_DEFINE2(ioprio_get, int, which, int, who) 176 { 177 struct task_struct *g, *p; 178 struct user_struct *user; 179 struct pid *pgrp; 180 kuid_t uid; 181 int ret = -ESRCH; 182 int tmpio; 183 184 rcu_read_lock(); 185 switch (which) { 186 case IOPRIO_WHO_PROCESS: 187 if (!who) 188 p = current; 189 else 190 p = find_task_by_vpid(who); 191 if (p) 192 ret = get_task_ioprio(p); 193 break; 194 case IOPRIO_WHO_PGRP: 195 if (!who) 196 pgrp = task_pgrp(current); 197 else 198 pgrp = find_vpid(who); 199 do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { 200 tmpio = get_task_ioprio(p); 201 if (tmpio < 0) 202 continue; 203 if (ret == -ESRCH) 204 ret = tmpio; 205 else 206 ret = ioprio_best(ret, tmpio); 207 } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); 208 break; 209 case IOPRIO_WHO_USER: 210 uid = make_kuid(current_user_ns(), who); 211 if (!who) 212 user = current_user(); 213 else 214 user = find_user(uid); 215 216 if (!user) 217 break; 218 219 for_each_process_thread(g, p) { 220 if (!uid_eq(task_uid(p), user->uid) || 221 !task_pid_vnr(p)) 222 continue; 223 tmpio = get_task_ioprio(p); 224 if (tmpio < 0) 225 continue; 226 if (ret == -ESRCH) 227 ret = tmpio; 228 else 229 ret = ioprio_best(ret, tmpio); 230 } 231 232 if (who) 233 free_uid(user); 234 break; 235 default: 236 ret = -EINVAL; 237 } 238 239 rcu_read_unlock(); 240 return ret; 241 } 242