xfs: fix pagecache truncation prior to reflink

Prior to remapping blocks, it is necessary to remove pages from the
destination file's page cache.  Unfortunately, the truncation is not
aggressive enough -- if page size > block size, we'll end up zeroing
subpage blocks instead of removing them.  So, round the start offset
down and the end offset up to page boundaries.  We already wrote all
the dirty data so the larger range shouldn't be a problem.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 9b1ea42c81d1..e8e86646bb4b 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1369,8 +1369,9 @@ xfs_reflink_remap_prep(
                 goto out_unlock;
 
         /* Zap any page cache for the destination file's range. */
-        truncate_inode_pages_range(&inode_out->i_data, pos_out,
-                                   PAGE_ALIGN(pos_out + *len) - 1);
+        truncate_inode_pages_range(&inode_out->i_data,
+                        round_down(pos_out, PAGE_SIZE),
+                        round_up(pos_out + *len, PAGE_SIZE) - 1);
 
         return 1;
 out_unlock: