ext4: Convert truncate_mutex to read write semaphore.

We are currently taking the truncate_mutex for every read. This would have
performance impact on large CPU configuration. Convert the lock to read write
semaphore and take read lock when we are trying to read the file.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index a6b2aa14626e..ac35ec58db55 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -37,9 +37,9 @@ static int ext4_release_file (struct inode * inode, struct file * filp)
         if ((filp->f_mode & FMODE_WRITE) &&
                         (atomic_read(&inode->i_writecount) == 1))
         {
-                mutex_lock(&EXT4_I(inode)->truncate_mutex);
+                down_write(&EXT4_I(inode)->i_data_sem);
                 ext4_discard_reservation(inode);
-                mutex_unlock(&EXT4_I(inode)->truncate_mutex);
+                up_write(&EXT4_I(inode)->i_data_sem);
         }
         if (is_dx(inode) && filp->private_data)
                 ext4_htree_free_dir_info(filp->private_data);