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-rw-r--r--block/ioprio.c278
1 files changed, 278 insertions, 0 deletions
diff --git a/block/ioprio.c b/block/ioprio.c
new file mode 100644
index 000000000..32a456b45
--- /dev/null
+++ b/block/ioprio.c
@@ -0,0 +1,278 @@
+// 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/ioprio.h>
+#include <linux/cred.h>
+#include <linux/blkdev.h>
+#include <linux/capability.h>
+#include <linux/syscalls.h>
+#include <linux/security.h>
+#include <linux/pid_namespace.h>
+
+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_NR_LEVELS || 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);
+
+ read_lock(&tasklist_lock);
+ do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
+ ret = set_task_ioprio(p, ioprio);
+ if (ret) {
+ read_unlock(&tasklist_lock);
+ goto out;
+ }
+ } 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 (!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;
+ }
+
+out:
+ rcu_read_unlock();
+ return ret;
+}
+
+/*
+ * If the task has set an I/O priority, use that. Otherwise, return
+ * the default I/O priority.
+ *
+ * Expected to be called for current task or with task_lock() held to keep
+ * io_context stable.
+ */
+int __get_task_ioprio(struct task_struct *p)
+{
+ struct io_context *ioc = p->io_context;
+ int prio;
+
+ if (p != current)
+ lockdep_assert_held(&p->alloc_lock);
+ if (ioc)
+ prio = ioc->ioprio;
+ else
+ prio = IOPRIO_DEFAULT;
+
+ if (IOPRIO_PRIO_CLASS(prio) == IOPRIO_CLASS_NONE)
+ prio = IOPRIO_PRIO_VALUE(task_nice_ioclass(p),
+ task_nice_ioprio(p));
+ return prio;
+}
+EXPORT_SYMBOL_GPL(__get_task_ioprio);
+
+static int get_task_ioprio(struct task_struct *p)
+{
+ int ret;
+
+ ret = security_task_getioprio(p);
+ if (ret)
+ goto out;
+ task_lock(p);
+ ret = __get_task_ioprio(p);
+ task_unlock(p);
+out:
+ return ret;
+}
+
+/*
+ * Return raw IO priority value as set by userspace. We use this for
+ * ioprio_get(pid, IOPRIO_WHO_PROCESS) so that we keep historical behavior and
+ * also so that userspace can distinguish unset IO priority (which just gets
+ * overriden based on task's nice value) from IO priority set to some value.
+ */
+static int get_task_raw_ioprio(struct task_struct *p)
+{
+ int ret;
+
+ ret = security_task_getioprio(p);
+ if (ret)
+ goto out;
+ task_lock(p);
+ if (p->io_context)
+ ret = p->io_context->ioprio;
+ else
+ ret = IOPRIO_DEFAULT;
+ task_unlock(p);
+out:
+ return ret;
+}
+
+static int ioprio_best(unsigned short aprio, unsigned short bprio)
+{
+ 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_raw_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;
+}
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