[PATCH V10 12/12] Btrfs: btrfs_ioctl_clone: Truncate complete page after performing clone operation

[Chandan Rajendra <chandan@linux.vnet.ibm.com>]

In subpagesize-blocksize scenario, the "destination offset" argument passed to
the btrfs_ioctl_clone() can be aligned to sectorsize but may not be
necessarily aligned to the machine's page size. In such cases,
truncate_inode_pages_range() ends up zeroing out the partial page and future
read operations will return incorrect data. Hence this commit explicitly
rounds down the "destination offset" to the machine's page size.

Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
---
 fs/btrfs/ioctl.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 8bbecda..4e11059 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3914,8 +3914,9 @@ static noinline long btrfs_ioctl_clone(struct file *file, unsigned long srcfd,
 	 * Truncate page cache pages so that future reads will see the cloned
 	 * data immediately and not the previous data.
 	 */
-	truncate_inode_pages_range(&inode->i_data, destoff,
-				   PAGE_CACHE_ALIGN(destoff + len) - 1);
+	truncate_inode_pages_range(&inode->i_data,
+				round_down(destoff, PAGE_CACHE_SIZE),
+				round_up(destoff + len, PAGE_CACHE_SIZE) - 1);
 out_unlock:
 	if (!same_inode)
 		btrfs_double_inode_unlock(src, inode);
-- 
2.1.0