[ 53/75] block: use i_size_write() in bd_set_size()

[Greg Kroah-Hartman]

3.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Guo Chao <yan@xxxxxxxxxxxxxxxxxx>

commit d646a02a9d44d1421f273ae3923d97b47b918176 upstream.

blkdev_ioctl(GETBLKSIZE) uses i_size_read() to read size of block device.
If we update block size directly, reader may see intermediate result in
some machines and configurations.  Use i_size_write() instead.

Signed-off-by: Guo Chao <yan@xxxxxxxxxxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Guo Chao <yan@xxxxxxxxxxxxxxxxxx>
Cc: M. Hindess <hindessm@xxxxxxxxxx>
Cc: Nikanth Karthikesan <knikanth@xxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Acked-by: Jeff Mahoney <jeffm@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/block_dev.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1033,7 +1033,9 @@ void bd_set_size(struct block_device *bd
 {
 	unsigned bsize = bdev_logical_block_size(bdev);
 
-	bdev->bd_inode->i_size = size;
+	mutex_lock(&bdev->bd_inode->i_mutex);
+	i_size_write(bdev->bd_inode, size);
+	mutex_unlock(&bdev->bd_inode->i_mutex);
 	while (bsize < PAGE_CACHE_SIZE) {
 		if (size & bsize)
 			break;


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