blob: 01b8116298a13b5463e7969ce66c0b037bcfccd5
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 |