diff options
Diffstat (limited to 'fs/ioprio.c')
| -rw-r--r-- | fs/ioprio.c | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/fs/ioprio.c b/fs/ioprio.c new file mode 100644 index 000000000000..97e1f088ba00 --- /dev/null +++ b/fs/ioprio.c @@ -0,0 +1,172 @@ +/* + * fs/ioprio.c + * + * Copyright (C) 2004 Jens Axboe <axboe@suse.de> + * + * 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.txt + * + */ +#include <linux/kernel.h> +#include <linux/ioprio.h> +#include <linux/blkdev.h> + +static int set_task_ioprio(struct task_struct *task, int ioprio) +{ + struct io_context *ioc; + + if (task->uid != current->euid && + task->uid != current->uid && !capable(CAP_SYS_NICE)) + return -EPERM; + + task_lock(task); + + task->ioprio = ioprio; + + ioc = task->io_context; + if (ioc && ioc->set_ioprio) + ioc->set_ioprio(ioc, ioprio); + + task_unlock(task); + return 0; +} + +asmlinkage long sys_ioprio_set(int which, int who, int ioprio) +{ + int class = IOPRIO_PRIO_CLASS(ioprio); + int data = IOPRIO_PRIO_DATA(ioprio); + struct task_struct *p, *g; + struct user_struct *user; + int ret; + + switch (class) { + case IOPRIO_CLASS_RT: + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + /* fall through, rt has prio field too */ + case IOPRIO_CLASS_BE: + if (data >= IOPRIO_BE_NR || data < 0) + return -EINVAL; + + break; + case IOPRIO_CLASS_IDLE: + break; + default: + return -EINVAL; + } + + ret = -ESRCH; + read_lock_irq(&tasklist_lock); + switch (which) { + case IOPRIO_WHO_PROCESS: + if (!who) + p = current; + else + p = find_task_by_pid(who); + if (p) + ret = set_task_ioprio(p, ioprio); + break; + case IOPRIO_WHO_PGRP: + if (!who) + who = process_group(current); + do_each_task_pid(who, PIDTYPE_PGID, p) { + ret = set_task_ioprio(p, ioprio); + if (ret) + break; + } while_each_task_pid(who, PIDTYPE_PGID, p); + break; + case IOPRIO_WHO_USER: + if (!who) + user = current->user; + else + user = find_user(who); + + if (!user) + break; + + do_each_thread(g, p) { + if (p->uid != who) + continue; + ret = set_task_ioprio(p, ioprio); + if (ret) + break; + } while_each_thread(g, p); + + if (who) + free_uid(user); + break; + default: + ret = -EINVAL; + } + + read_unlock_irq(&tasklist_lock); + return ret; +} + +asmlinkage long sys_ioprio_get(int which, int who) +{ + struct task_struct *g, *p; + struct user_struct *user; + int ret = -ESRCH; + + read_lock_irq(&tasklist_lock); + switch (which) { + case IOPRIO_WHO_PROCESS: + if (!who) + p = current; + else + p = find_task_by_pid(who); + if (p) + ret = p->ioprio; + break; + case IOPRIO_WHO_PGRP: + if (!who) + who = process_group(current); + do_each_task_pid(who, PIDTYPE_PGID, p) { + if (ret == -ESRCH) + ret = p->ioprio; + else + ret = ioprio_best(ret, p->ioprio); + } while_each_task_pid(who, PIDTYPE_PGID, p); + break; + case IOPRIO_WHO_USER: + if (!who) + user = current->user; + else + user = find_user(who); + + if (!user) + break; + + do_each_thread(g, p) { + if (p->uid != user->uid) + continue; + if (ret == -ESRCH) + ret = p->ioprio; + else + ret = ioprio_best(ret, p->ioprio); + } while_each_thread(g, p); + + if (who) + free_uid(user); + break; + default: + ret = -EINVAL; + } + + read_unlock_irq(&tasklist_lock); + return ret; +} + |