tty: implement write_iter

This makes the tty layer use the .write_iter() function instead of the
traditional .write() functionality.

That allows writev(), but more importantly also makes it possible to
enable .splice_write() for ttys, reinstating the "splice to tty"
functionality that was lost in commit 36e2c7421f02 ("fs: don't allow
splice read/write without explicit ops").

Fixes: 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops")
Reported-by: Oliver Giles <ohw.giles@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 56ade99..338bc4e 100644 (file)
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -143,9 +143,8 @@ LIST_HEAD(tty_drivers);                     /* linked list of tty drivers */
 DEFINE_MUTEX(tty_mutex);
 
 static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);
-static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);
-ssize_t redirected_tty_write(struct file *, const char __user *,
-                                                       size_t, loff_t *);
+static ssize_t tty_write(struct kiocb *, struct iov_iter *);
+ssize_t redirected_tty_write(struct kiocb *, struct iov_iter *);
 static __poll_t tty_poll(struct file *, poll_table *);
 static int tty_open(struct inode *, struct file *);
 long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
@@ -478,7 +477,8 @@ static void tty_show_fdinfo(struct seq_file *m, struct file *file)
 static const struct file_operations tty_fops = {
        .llseek         = no_llseek,
        .read           = tty_read,
-       .write          = tty_write,
+       .write_iter     = tty_write,
+       .splice_write   = iter_file_splice_write,
        .poll           = tty_poll,
        .unlocked_ioctl = tty_ioctl,
        .compat_ioctl   = tty_compat_ioctl,
@@ -491,7 +491,8 @@ static const struct file_operations tty_fops = {
 static const struct file_operations console_fops = {
        .llseek         = no_llseek,
        .read           = tty_read,
-       .write          = redirected_tty_write,
+       .write_iter     = redirected_tty_write,
+       .splice_write   = iter_file_splice_write,
        .poll           = tty_poll,
        .unlocked_ioctl = tty_ioctl,
        .compat_ioctl   = tty_compat_ioctl,
@@ -607,9 +608,9 @@ static void __tty_hangup(struct tty_struct *tty, int exit_session)
        /* This breaks for file handles being sent over AF_UNIX sockets ? */
        list_for_each_entry(priv, &tty->tty_files, list) {
                filp = priv->file;
-               if (filp->f_op->write == redirected_tty_write)
+               if (filp->f_op->write_iter == redirected_tty_write)
                        cons_filp = filp;
-               if (filp->f_op->write != tty_write)
+               if (filp->f_op->write_iter != tty_write)
                        continue;
                closecount++;
                __tty_fasync(-1, filp, 0);      /* can't block */
@@ -902,9 +903,9 @@ static inline ssize_t do_tty_write(
        ssize_t (*write)(struct tty_struct *, struct file *, const unsigned char *, size_t),
        struct tty_struct *tty,
        struct file *file,
-       const char __user *buf,
-       size_t count)
+       struct iov_iter *from)
 {
+       size_t count = iov_iter_count(from);
        ssize_t ret, written = 0;
        unsigned int chunk;
 
@@ -956,14 +957,20 @@ static inline ssize_t do_tty_write(
                size_t size = count;
                if (size > chunk)
                        size = chunk;
+
                ret = -EFAULT;
-               if (copy_from_user(tty->write_buf, buf, size))
+               if (copy_from_iter(tty->write_buf, size, from) != size)
                        break;
+
                ret = write(tty, file, tty->write_buf, size);
                if (ret <= 0)
                        break;
+
+               /* FIXME! Have Al check this! */
+               if (ret != size)
+                       iov_iter_revert(from, size-ret);
+
                written += ret;
-               buf += ret;
                count -= ret;
                if (!count)
                        break;
@@ -1023,9 +1030,9 @@ void tty_write_message(struct tty_struct *tty, char *msg)
  *     write method will not be invoked in parallel for each device.
  */
 
-static ssize_t tty_write(struct file *file, const char __user *buf,
-                                               size_t count, loff_t *ppos)
+static ssize_t tty_write(struct kiocb *iocb, struct iov_iter *from)
 {
+       struct file *file = iocb->ki_filp;
        struct tty_struct *tty = file_tty(file);
        struct tty_ldisc *ld;
        ssize_t ret;
@@ -1038,18 +1045,15 @@ static ssize_t tty_write(struct file *file, const char __user *buf,
        if (tty->ops->write_room == NULL)
                tty_err(tty, "missing write_room method\n");
        ld = tty_ldisc_ref_wait(tty);
-       if (!ld)
-               return hung_up_tty_write(file, buf, count, ppos);
-       if (!ld->ops->write)
+       if (!ld || !ld->ops->write)
                ret = -EIO;
        else
-               ret = do_tty_write(ld->ops->write, tty, file, buf, count);
+               ret = do_tty_write(ld->ops->write, tty, file, from);
        tty_ldisc_deref(ld);
        return ret;
 }
 
-ssize_t redirected_tty_write(struct file *file, const char __user *buf,
-                                               size_t count, loff_t *ppos)
+ssize_t redirected_tty_write(struct kiocb *iocb, struct iov_iter *iter)
 {
        struct file *p = NULL;
 
@@ -1060,11 +1064,11 @@ ssize_t redirected_tty_write(struct file *file, const char __user *buf,
 
        if (p) {
                ssize_t res;
-               res = vfs_write(p, buf, count, &p->f_pos);
+               res = vfs_iocb_iter_write(p, iocb, iter);
                fput(p);
                return res;
        }
-       return tty_write(file, buf, count, ppos);
+       return tty_write(iocb, iter);
 }
 
 /**
@@ -2293,7 +2297,7 @@ static int tioccons(struct file *file)
 {
        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;
-       if (file->f_op->write == redirected_tty_write) {
+       if (file->f_op->write_iter == redirected_tty_write) {
                struct file *f;
                spin_lock(&redirect_lock);
                f = redirect;