xfs: fix pagecache truncation prior to reflink

commit 4918ef4ea008cd2ff47eb852894e3f9b9047f4f3 upstream.

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>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 7088f44c0c5947d4fccf5df4315d56158e8da5c3..38ea08a3dd1d0456d83f66bd2ede919c77d44e76 100644 (file)
--- 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);
 
        /* If we're altering the file contents... */
        if (!is_dedupe) {