ext4: don't take the i_mutex lock when doing DIO overwrites

[firefly-linux-kernel-4.4.55.git] / fs / ext4 / inode.c

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 76cb3b1ad78a7ffa4b14410980e50059ce993825..bed574dd4c22c9998fb8644656e73a05bf451835 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2996,6 +2996,16 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb,
        if (rw == WRITE && final_size <= inode->i_size) {
                int overwrite = 0;
 
+               BUG_ON(iocb->private == NULL);
+
+               /* If we do a overwrite dio, i_mutex locking can be released */
+               overwrite = *((int *)iocb->private);
+
+               if (overwrite) {
+                       down_read(&EXT4_I(inode)->i_data_sem);
+                       mutex_unlock(&inode->i_mutex);
+               }
+
                /*
                 * We could direct write to holes and fallocate.
                 *
@@ -3021,8 +3031,10 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb,
                if (!is_sync_kiocb(iocb)) {
                        ext4_io_end_t *io_end =
                                ext4_init_io_end(inode, GFP_NOFS);
-                       if (!io_end)
-                               return -ENOMEM;
+                       if (!io_end) {
+                               ret = -ENOMEM;
+                               goto retake_lock;
+                       }
                        io_end->flag |= EXT4_IO_END_DIRECT;
                        iocb->private = io_end;
                        /*
@@ -3083,6 +3095,14 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb,
                                ret = err;
                        ext4_clear_inode_state(inode, EXT4_STATE_DIO_UNWRITTEN);
                }
+
+       retake_lock:
+               /* take i_mutex locking again if we do a ovewrite dio */
+               if (overwrite) {
+                       up_read(&EXT4_I(inode)->i_data_sem);
+                       mutex_lock(&inode->i_mutex);
+               }
+
                return ret;
        }