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Subject[53/90] ext4: fix ext4_ext_direct_IO()s return value after converting uninit extents
2.6.31-stable review patch.  If anyone has any objections, please let us know.

------------------
(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;
}




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