[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>

2 files changed, 7 insertions, 5 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;
 }
 
diff --git a/arch/sparc64/solaris/ioctl.c b/arch/sparc64/solaris/ioctl.c
index 374766455f5e..be0a054e3ed6 100644
--- a/arch/sparc64/solaris/ioctl.c
+++ b/arch/sparc64/solaris/ioctl.c
@@ -24,6 +24,7 @@
 #include <linux/netdevice.h>
 #include <linux/mtio.h>
 #include <linux/time.h>
+#include <linux/rcupdate.h>
 #include <linux/compat.h>
 
 #include <net/sock.h>
@@ -295,16 +296,16 @@ static inline int solaris_sockmod(unsigned int fd, unsigned int cmd, u32 arg)
         struct inode *ino;
         struct fdtable *fdt;
         /* I wonder which of these tests are superfluous... --patrik */
-        spin_lock(&current->files->file_lock);
+        rcu_read_lock();
         fdt = files_fdtable(current->files);
         if (! fdt->fd[fd] ||
             ! fdt->fd[fd]->f_dentry ||
             ! (ino = fdt->fd[fd]->f_dentry->d_inode) ||
             ! S_ISSOCK(ino->i_mode)) {
-                spin_unlock(&current->files->file_lock);
+                rcu_read_unlock();
                 return TBADF;
         }
-        spin_unlock(&current->files->file_lock);
+        rcu_read_unlock();
         
         switch (cmd & 0xff) {
         case 109: /* SI_SOCKPARAMS */