| 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 | } |