int set_task_ioprio(struct task_struct *task, int ioprio)
{
#ifdef CONFIG_IOSCHED_BFQ
int err, i;
#else
int err;
#endif
struct io_context *ioc;
const struct cred *cred = current_cred(), *tcred;
rcu_read_lock();
tcred = __task_cred(task);
if (tcred->uid != cred->euid &&
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;
task_lock(task);
do {
ioc = task->io_context;
/* see wmb() in current_io_context() */
smp_read_barrier_depends();
if (ioc)
break;
ioc = alloc_io_context(GFP_ATOMIC, -1);
if (!ioc) {
err = -ENOMEM;
break;
}
#ifdef CONFIG_IOSCHED_BFQ
/* let other ioc users see the new values */
smp_wmb();
#endif
task->io_context = ioc;
} while (1);
if (!err) {
ioc->ioprio = ioprio;
#ifdef CONFIG_IOSCHED_BFQ
/* make sure schedulers see the new ioprio value */
wmb();
for (i = 0; i < IOC_IOPRIO_CHANGED_BITS; i++)
set_bit(i, ioc->ioprio_changed);
#else
ioc->ioprio_changed = 1;
#endif
}
task_unlock(task);
return err;
}
int set_task_ioprio(struct task_struct *task, int ioprio)
{
int err, i;
struct io_context *ioc;
const struct cred *cred = current_cred(), *tcred;
rcu_read_lock();
tcred = __task_cred(task);
if (tcred->uid != cred->euid &&
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;
task_lock(task);
do {
ioc = task->io_context;
/* see wmb() in current_io_context() */
smp_read_barrier_depends();
if (ioc)
break;
ioc = alloc_io_context(GFP_ATOMIC, -1);
if (!ioc) {
err = -ENOMEM;
break;
}
smp_wmb();
task->io_context = ioc;
} while (1);
if (!err) {
ioc->ioprio = ioprio;
wmb();
for (i = 0; i < IOC_IOPRIO_CHANGED_BITS; i++)
set_bit(i, ioc->ioprio_changed);
}
task_unlock(task);
return err;
}
/*
* If the current task has no IO context then create one and initialise it.
* Otherwise, return its existing IO context.
*
* This returned IO context doesn't have a specifically elevated refcount,
* but since the current task itself holds a reference, the context can be
* used in general code, so long as it stays within `current` context.
*/
struct io_context *current_io_context(gfp_t gfp_flags, int node)
{
struct task_struct *tsk = current;
struct io_context *ret;
ret = tsk->io_context;
if (likely(ret))
return ret;
ret = alloc_io_context(gfp_flags, node);
if (ret) {
/* make sure set_task_ioprio() sees the settings above */
smp_wmb();
tsk->io_context = ret;
}
return ret;
}
static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
{
#ifdef CONFIG_BLOCK
struct io_context *ioc = current->io_context;
if (!ioc)
return 0;
/*
* Share io context with parent, if CLONE_IO is set
*/
if (clone_flags & CLONE_IO) {
tsk->io_context = ioc_task_link(ioc);
if (unlikely(!tsk->io_context))
return -ENOMEM;
} else if (ioprio_valid(ioc->ioprio)) {
tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
if (unlikely(!tsk->io_context))
return -ENOMEM;
tsk->io_context->ioprio = ioc->ioprio;
}
#endif
return 0;
}