[PATCH] files: lock-free fd look-up

With the use of RCU in files structure, the look-up of files using fds can now
be lock-free.  The lookup is protected by rcu_read_lock()/rcu_read_unlock().
This patch changes the readers to use lock-free lookup.

Signed-off-by: Maneesh Soni <maneesh@in.ibm.com>
Signed-off-by: Ravikiran Thirumalai <kiran_th@gmail.com>
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/arch/mips/kernel/irixioctl.c b/arch/mips/kernel/irixioctl.c
index 4cd3d38a22c2..3cdc22346f4c 100644
--- a/arch/mips/kernel/irixioctl.c
+++ b/arch/mips/kernel/irixioctl.c
@@ -14,6 +14,7 @@
 #include <linux/syscalls.h>
 #include <linux/tty.h>
 #include <linux/file.h>
+#include <linux/rcupdate.h>
 
 #include <asm/uaccess.h>
 #include <asm/ioctl.h>
@@ -33,7 +34,7 @@ static struct tty_struct *get_tty(int fd)
         struct file *filp;
         struct tty_struct *ttyp = NULL;
 
-        spin_lock(&current->files->file_lock);
+        rcu_read_lock();
         filp = fcheck(fd);
         if(filp && filp->private_data) {
                 ttyp = (struct tty_struct *) filp->private_data;
@@ -41,7 +42,7 @@ static struct tty_struct *get_tty(int fd)
                 if(ttyp->magic != TTY_MAGIC)
                         ttyp =NULL;
         }
-        spin_unlock(&current->files->file_lock);
+        rcu_read_unlock();
         return ttyp;
 }