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>

2 files changed, 23 insertions, 9 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)
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 0350c42375a2..cd5b829634ea 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -136,6 +136,9 @@ LIST_HEAD(tty_drivers);			/* linked list of tty drivers */
 DEFINE_MUTEX(tty_mutex);
 EXPORT_SYMBOL(tty_mutex);
 
+/* Spinlock to protect the tty->tty_files list */
+DEFINE_SPINLOCK(tty_files_lock);
+
 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 *,
@@ -235,11 +238,11 @@ static int check_tty_count(struct tty_struct *tty, const char *routine)
         struct list_head *p;
         int count = 0;
 
-        file_list_lock();
+        spin_lock(&tty_files_lock);
         list_for_each(p, &tty->tty_files) {
                 count++;
         }
-        file_list_unlock();
+        spin_unlock(&tty_files_lock);
         if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
             tty->driver->subtype == PTY_TYPE_SLAVE &&
             tty->link && tty->link->count)
@@ -519,7 +522,7 @@ void __tty_hangup(struct tty_struct *tty)
            workqueue with the lock held */
         check_tty_count(tty, "tty_hangup");
 
-        file_list_lock();
+        spin_lock(&tty_files_lock);
         /* This breaks for file handles being sent over AF_UNIX sockets ? */
         list_for_each_entry(filp, &tty->tty_files, f_u.fu_list) {
                 if (filp->f_op->write == redirected_tty_write)
@@ -530,7 +533,7 @@ void __tty_hangup(struct tty_struct *tty)
                 __tty_fasync(-1, filp, 0);      /* can't block */
                 filp->f_op = &hung_up_tty_fops;
         }
-        file_list_unlock();
+        spin_unlock(&tty_files_lock);
 
         tty_ldisc_hangup(tty);
 
@@ -1424,9 +1427,9 @@ static void release_one_tty(struct work_struct *work)
         tty_driver_kref_put(driver);
         module_put(driver->owner);
 
-        file_list_lock();
+        spin_lock(&tty_files_lock);
         list_del_init(&tty->tty_files);
-        file_list_unlock();
+        spin_unlock(&tty_files_lock);
 
         put_pid(tty->pgrp);
         put_pid(tty->session);
@@ -1671,7 +1674,10 @@ int tty_release(struct inode *inode, struct file *filp)
          *  - do_tty_hangup no longer sees this file descriptor as
          *    something that needs to be handled for hangups.
          */
-        file_kill(filp);
+        spin_lock(&tty_files_lock);
+        BUG_ON(list_empty(&filp->f_u.fu_list));
+        list_del_init(&filp->f_u.fu_list);
+        spin_unlock(&tty_files_lock);
         filp->private_data = NULL;
 
         /*
@@ -1840,7 +1846,11 @@ got_driver:
         }
 
         filp->private_data = tty;
-        file_move(filp, &tty->tty_files);
+        BUG_ON(list_empty(&filp->f_u.fu_list));
+        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);
         check_tty_count(tty, "tty_open");
         if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
             tty->driver->subtype == PTY_TYPE_MASTER)