/*
* Lightweight file lookup - no refcnt increment if fd table isn't shared.
* You can use this only if it is guranteed that the current task already
* holds a refcnt to that file. That check has to be done at fget() only
* and a flag is returned to be passed to the corresponding fput_light().
* There must not be a cloning between an fget_light/fput_light pair.
*/
struct file *fget_light(unsigned int fd, int *fput_needed)
{
struct file *file;
struct files_struct *files = current->files;
*fput_needed = 0;
if (likely((atomic_read(&files->count) == 1))) {
file = fcheck_files(files, fd);
if (unlikely(file && file->f_heavy))
goto slow;
} else {
slow:
rcu_read_lock();
file = fcheck_files(files, fd);
if (file) {
if (atomic_long_inc_not_zero(&file->f_count))
*fput_needed = 1;
else
/* Didn't get the reference, someone's freed */
file = NULL;
}
rcu_read_unlock();
}
return file;
}
/* Actually fget_light is defined in fs/file.c but only 3.7 exports it.
* Lets export it here.
*/
struct file *fget_light(unsigned int fd, int *fput_needed)
{
struct file *file;
struct files_struct *files = current->files;
*fput_needed = 0;
if (atomic_read(&files->count) == 1) {
file = fcheck_files(files, fd);
if (file && (file->f_mode & FMODE_PATH))
file = NULL;
} else {
rcu_read_lock();
file = fcheck_files(files, fd);
if (file) {
if (!(file->f_mode & FMODE_PATH) &&
atomic_long_inc_not_zero(&file->f_count))
*fput_needed = 1;
else
/* Didn't get the reference, someone's freed */
file = NULL;
}
rcu_read_unlock();
}
return file;
}
static struct bsd_acct_struct *acct_get(struct pid_namespace *ns)
{
struct bsd_acct_struct *res;
again:
smp_rmb();
rcu_read_lock();
res = to_acct(ACCESS_ONCE(ns->bacct));
if (!res) {
rcu_read_unlock();
return NULL;
}
if (!atomic_long_inc_not_zero(&res->count)) {
rcu_read_unlock();
cpu_relax();
goto again;
}
rcu_read_unlock();
mutex_lock(&res->lock);
if (res != to_acct(ACCESS_ONCE(ns->bacct))) {
mutex_unlock(&res->lock);
acct_put(res);
goto again;
}
return res;
}
/*
* If the current task has no IO context then create one and initialise it.
* If it does have a context, take a ref on it.
*
* This is always called in the context of the task which submitted the I/O.
*/
struct io_context *get_io_context(gfp_t gfp_flags, int node)
{
struct io_context *ioc = NULL;
/*
* Check for unlikely race with exiting task. ioc ref count is
* zero when ioc is being detached.
*/
do {
ioc = current_io_context(gfp_flags, node);
if (unlikely(!ioc))
break;
} while (!atomic_long_inc_not_zero(&ioc->refcount));
return ioc;
}
struct file *fget_raw(unsigned int fd)
{
struct file *file;
struct files_struct *files = current->files;
rcu_read_lock();
file = fcheck_files(files, fd);
if (file) {
/* File object ref couldn't be taken */
if (!atomic_long_inc_not_zero(&file->f_count))
file = NULL;
}
rcu_read_unlock();
return file;
}
struct file *begin_import_dvfs_file(unsigned long dvfs_objid,
struct dvfs_file_struct **dvfs_file)
{
struct file *file = NULL;
/* Check if the file struct is already present */
*dvfs_file = grab_dvfs_file_struct(dvfs_objid);
file = (*dvfs_file)->file;
/* Check for a race with last fput()->__fput() */
if (file && !atomic_long_inc_not_zero(&file->f_count)) {
(*dvfs_file)->file = NULL;
file = NULL;
}
return file;
}
struct file *fget(unsigned int fd)
{
struct file *file;
struct files_struct *files = current->files;
rcu_read_lock();
file = fcheck_files(files, fd);
if (file) {
/* */
if (file->f_mode & FMODE_PATH ||
!atomic_long_inc_not_zero(&file->f_count))
file = NULL;
}
rcu_read_unlock();
return file;
}
static struct file *
fget_from_files(struct files_struct *files, unsigned fd)
{
struct file *file;
rcu_read_lock();
file = fcheck_files(files, fd);
if (file) {
if (file->f_mode & FMODE_PATH ||
!atomic_long_inc_not_zero(&file->f_count)) {
file = NULL;
}
}
rcu_read_unlock();
return file;
}
struct file *fget_raw_light(unsigned int fd, int *fput_needed)
{
struct file *file;
struct files_struct *files = current->files;
*fput_needed = 0;
if (atomic_read(&files->count) == 1) {
file = fcheck_files(files, fd);
} else {
rcu_read_lock();
file = fcheck_files(files, fd);
if (file) {
if (atomic_long_inc_not_zero(&file->f_count))
*fput_needed = 1;
else
/* */
file = NULL;
}
rcu_read_unlock();
}
return file;
}
static long
fd_link_ioctl (struct file *f, unsigned int ioctl, unsigned long arg)
{
void __user *argp = (void __user *) arg;
struct task_struct *task_target = NULL;
struct file *file;
struct files_struct *files;
struct fdtable *fdt;
struct fd_copy fd_copy;
switch (ioctl)
{
case FD_COPY:
if (copy_from_user (&fd_copy, argp, sizeof (struct fd_copy)))
return -EFAULT;
/*
* Find the task struct for the target pid
*/
task_target =
pid_task (find_vpid (fd_copy.target_pid), PIDTYPE_PID);
if (task_target == NULL)
{
printk (KERN_DEBUG "Failed to get mem ctx for target pid\n");
return -EFAULT;
}
files = get_files_struct (current);
if (files == NULL)
{
printk (KERN_DEBUG "Failed to get files struct\n");
return -EFAULT;
}
rcu_read_lock ();
file = fcheck_files (files, fd_copy.source_fd);
if (file)
{
if (file->f_mode & FMODE_PATH
|| !atomic_long_inc_not_zero (&file->f_count))
file = NULL;
}
rcu_read_unlock ();
put_files_struct (files);
if (file == NULL)
{
printk (KERN_DEBUG "Failed to get file from source pid\n");
return 0;
}
/*
* Release the existing fd in the source process
*/
spin_lock (&files->file_lock);
filp_close (file, files);
fdt = files_fdtable (files);
fdt->fd[fd_copy.source_fd] = NULL;
spin_unlock (&files->file_lock);
/*
* Find the file struct associated with the target fd.
*/
files = get_files_struct (task_target);
if (files == NULL)
{
printk (KERN_DEBUG "Failed to get files struct\n");
return -EFAULT;
}
rcu_read_lock ();
file = fcheck_files (files, fd_copy.target_fd);
if (file)
{
if (file->f_mode & FMODE_PATH
|| !atomic_long_inc_not_zero (&file->f_count))
file = NULL;
}
rcu_read_unlock ();
put_files_struct (files);
if (file == NULL)
{
printk (KERN_DEBUG "Failed to get file from target pid\n");
return 0;
}
/*
* Install the file struct from the target process into the
* file desciptor of the source process,
*/
fd_install (fd_copy.source_fd, file);
return 0;
default:
return -ENOIOCTLCMD;
}
}
