fs: cleanup files_lock locking

fs: cleanup files_lock locking

Lock tty_files with a new spinlock, tty_files_lock; provide helpers to
manipulate the per-sb files list; unexport the files_lock spinlock.

Cc: linux-kernel@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Acked-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 5 insertions, 1 deletions

diff --git a/drivers/char/pty.c b/drivers/char/pty.c
index ad46eae1f9bb..2c64faa8efa4 100644
--- a/drivers/char/pty.c
+++ b/drivers/char/pty.c
@@ -676,7 +676,11 @@ static int ptmx_open(struct inode *inode, struct file *filp)
 
         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
         filp->private_data = tty;
-        file_move(filp, &tty->tty_files);
+
+        file_sb_list_del(filp); /* __dentry_open has put it on the sb list */
+        spin_lock(&tty_files_lock);
+        list_add(&filp->f_u.fu_list, &tty->tty_files);
+        spin_unlock(&tty_files_lock);
 
         retval = devpts_pty_new(inode, tty->link);
         if (retval)