releases/2.6.31.8/0053-ext4-fix-ext4_ext_direct_IO-s-return-value-after-con.patch

From acd8eefddb85238ffd6ed9f67a159007d3de7254 Mon Sep 17 00:00:00 2001
From: Mingming <cmm@us.ibm.com>
Date: Tue, 10 Nov 2009 10:48:08 -0500
Subject: [PATCH 53/85] ext4: fix ext4_ext_direct_IO()'s return value after converting uninit extents

(cherry picked from commit 109f55651954def97fa41ee71c464d268c512ab0)

After a direct I/O request covering an uninitalized extent (i.e.,
created using the fallocate system call) or a hole in a file, ext4
will convert the uninitialized extent so it is marked as initialized
by calling ext4_convert_unwritten_extents().  This function returns
zero on success.

This return value was getting returned by ext4_direct_IO(); however
the file system's direct_IO function is supposed to return the number
of bytes read or written on a success.  By returning zero, it confused
the direct I/O code into falling back to buffered I/O unnecessarily.

Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
 fs/ext4/extents.c |    1 +
 fs/ext4/inode.c   |   10 +++++++---
 2 files changed, 8 insertions(+), 3 deletions(-)

--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3496,6 +3496,7 @@ retry:
  *
  * This function is called from the direct IO end io call back
  * function, to convert the fallocated extents after IO is completed.
+ * Returns 0 on success.
  */
 int ext4_convert_unwritten_extents(struct inode *inode, loff_t offset,
 				    loff_t len)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3766,13 +3766,17 @@ static ssize_t ext4_ext_direct_IO(int rw
 		if (ret != -EIOCBQUEUED && ret <= 0 && iocb->private) {
 			ext4_free_io_end(iocb->private);
 			iocb->private = NULL;
-		} else if (ret > 0)
+		} else if (ret > 0) {
+			int err;
 			/*
 			 * for non AIO case, since the IO is already
 			 * completed, we could do the convertion right here
 			 */
-			ret = ext4_convert_unwritten_extents(inode,
-								offset, ret);
+			err = ext4_convert_unwritten_extents(inode,
+							     offset, ret);
+			if (err < 0)
+				ret = err;
+		}
 		return ret;
 	}