diff options
Diffstat (limited to 'block/ioprio.c')
| -rw-r--r-- | block/ioprio.c | 262 |
1 files changed, 262 insertions, 0 deletions
diff --git a/block/ioprio.c b/block/ioprio.c new file mode 100644 index 000000000..c8878647d --- /dev/null +++ b/block/ioprio.c @@ -0,0 +1,262 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * fs/ioprio.c + * + * Copyright (C) 2004 Jens Axboe <axboe@kernel.dk> + * + * Helper functions for setting/querying io priorities of processes. The + * system calls closely mimmick getpriority/setpriority, see the man page for + * those. The prio argument is a composite of prio class and prio data, where + * the data argument has meaning within that class. The standard scheduling + * classes have 8 distinct prio levels, with 0 being the highest prio and 7 + * being the lowest. + * + * IOW, setting BE scheduling class with prio 2 is done ala: + * + * unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2; + * + * ioprio_set(PRIO_PROCESS, pid, prio); + * + * See also Documentation/block/ioprio.rst + * + */ +#include <linux/gfp.h> +#include <linux/kernel.h> +#include <linux/export.h> +#include <linux/ioprio.h> +#include <linux/cred.h> +#include <linux/blkdev.h> +#include <linux/capability.h> +#include <linux/sched/user.h> +#include <linux/sched/task.h> +#include <linux/syscalls.h> +#include <linux/security.h> +#include <linux/pid_namespace.h> + +int set_task_ioprio(struct task_struct *task, int ioprio) +{ + int err; + struct io_context *ioc; + const struct cred *cred = current_cred(), *tcred; + + rcu_read_lock(); + tcred = __task_cred(task); + if (!uid_eq(tcred->uid, cred->euid) && + !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) { + rcu_read_unlock(); + return -EPERM; + } + rcu_read_unlock(); + + err = security_task_setioprio(task, ioprio); + if (err) + return err; + + ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE); + if (ioc) { + ioc->ioprio = ioprio; + put_io_context(ioc); + } + + return err; +} +EXPORT_SYMBOL_GPL(set_task_ioprio); + +int ioprio_check_cap(int ioprio) +{ + int class = IOPRIO_PRIO_CLASS(ioprio); + int data = IOPRIO_PRIO_DATA(ioprio); + + switch (class) { + case IOPRIO_CLASS_RT: + /* + * Originally this only checked for CAP_SYS_ADMIN, + * which was implicitly allowed for pid 0 by security + * modules such as SELinux. Make sure we check + * CAP_SYS_ADMIN first to avoid a denial/avc for + * possibly missing CAP_SYS_NICE permission. + */ + if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_NICE)) + return -EPERM; + fallthrough; + /* rt has prio field too */ + case IOPRIO_CLASS_BE: + if (data >= IOPRIO_BE_NR || data < 0) + return -EINVAL; + + break; + case IOPRIO_CLASS_IDLE: + break; + case IOPRIO_CLASS_NONE: + if (data) + return -EINVAL; + break; + default: + return -EINVAL; + } + + return 0; +} + +SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio) +{ + struct task_struct *p, *g; + struct user_struct *user; + struct pid *pgrp; + kuid_t uid; + int ret; + + ret = ioprio_check_cap(ioprio); + if (ret) + return ret; + + ret = -ESRCH; + rcu_read_lock(); + switch (which) { + case IOPRIO_WHO_PROCESS: + if (!who) + p = current; + else + p = find_task_by_vpid(who); + if (p) + ret = set_task_ioprio(p, ioprio); + break; + case IOPRIO_WHO_PGRP: + if (!who) + pgrp = task_pgrp(current); + else + pgrp = find_vpid(who); + do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { + ret = set_task_ioprio(p, ioprio); + if (ret) + break; + } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); + break; + case IOPRIO_WHO_USER: + uid = make_kuid(current_user_ns(), who); + if (!uid_valid(uid)) + break; + if (!who) + user = current_user(); + else + user = find_user(uid); + + if (!user) + break; + + for_each_process_thread(g, p) { + if (!uid_eq(task_uid(p), uid) || + !task_pid_vnr(p)) + continue; + ret = set_task_ioprio(p, ioprio); + if (ret) + goto free_uid; + } +free_uid: + if (who) + free_uid(user); + break; + default: + ret = -EINVAL; + } + + rcu_read_unlock(); + return ret; +} + +static int get_task_ioprio(struct task_struct *p) +{ + int ret; + + ret = security_task_getioprio(p); + if (ret) + goto out; + ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM); + task_lock(p); + if (p->io_context) + ret = p->io_context->ioprio; + task_unlock(p); +out: + return ret; +} + +int ioprio_best(unsigned short aprio, unsigned short bprio) +{ + if (!ioprio_valid(aprio)) + aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM); + if (!ioprio_valid(bprio)) + bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM); + + return min(aprio, bprio); +} + +SYSCALL_DEFINE2(ioprio_get, int, which, int, who) +{ + struct task_struct *g, *p; + struct user_struct *user; + struct pid *pgrp; + kuid_t uid; + int ret = -ESRCH; + int tmpio; + + rcu_read_lock(); + switch (which) { + case IOPRIO_WHO_PROCESS: + if (!who) + p = current; + else + p = find_task_by_vpid(who); + if (p) + ret = get_task_ioprio(p); + break; + case IOPRIO_WHO_PGRP: + if (!who) + pgrp = task_pgrp(current); + else + pgrp = find_vpid(who); + read_lock(&tasklist_lock); + do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { + tmpio = get_task_ioprio(p); + if (tmpio < 0) + continue; + if (ret == -ESRCH) + ret = tmpio; + else + ret = ioprio_best(ret, tmpio); + } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); + read_unlock(&tasklist_lock); + + break; + case IOPRIO_WHO_USER: + uid = make_kuid(current_user_ns(), who); + if (!who) + user = current_user(); + else + user = find_user(uid); + + if (!user) + break; + + for_each_process_thread(g, p) { + if (!uid_eq(task_uid(p), user->uid) || + !task_pid_vnr(p)) + continue; + tmpio = get_task_ioprio(p); + if (tmpio < 0) + continue; + if (ret == -ESRCH) + ret = tmpio; + else + ret = ioprio_best(ret, tmpio); + } + + if (who) + free_uid(user); + break; + default: + ret = -EINVAL; + } + + rcu_read_unlock(); + return ret; +} |