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-rw-r--r--fs/ioprio.c172
1 files changed, 172 insertions, 0 deletions
diff --git a/fs/ioprio.c b/fs/ioprio.c
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+++ b/fs/ioprio.c
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+/*
+ * 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 int 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 int 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;
+}
+
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