fs-files_list-improve

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

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 23 insertions, 10 deletions

diff --git a/drivers/char/pty.c b/drivers/char/pty.c
index 385c44b3034f..8fa273e76bb3 100644
--- a/drivers/char/pty.c
+++ b/drivers/char/pty.c
@@ -649,7 +649,11 @@ 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 76253cf27028..38ddfa404fb1 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 *,
@@ -234,11 +237,11 @@ 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)
@@ -516,8 +519,7 @@ static void do_tty_hangup(struct work_struct *work)
         /* inuse_filps is protected by the single kernel lock */
         lock_kernel();
         check_tty_count(tty, "do_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)
@@ -528,7 +530,7 @@ static void do_tty_hangup(struct work_struct *work)
                 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);
 
@@ -1419,9 +1421,9 @@ 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);
@@ -1666,7 +1668,10 @@ 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;
 
         /*
@@ -1835,7 +1840,11 @@ 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)