fs: Do to trim high file position bits in iomap_page_mkwrite_actor

iomap_page_mkwrite_actor() calls __block_write_begin_int() with position
masked as pos & ~PAGE_MASK which is equivalent to pos & (PAGE_SIZE-1).
Thus it masks off high bits of file position. However
__block_write_begin_int() expects full file position on input. This does
not cause any visible issues because all __block_write_begin_int()
really cares about are low file position bits but still it is a bug
waiting to happen.

Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --git a/fs/iomap.c b/fs/iomap.c
index a92204012e2d825085605d544243c2e81bcb583f..a8ee8c33ca782dbe4a4c17f42bf91fda9e83a523 100644 (file)
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -433,8 +433,7 @@ iomap_page_mkwrite_actor(struct inode *inode, loff_t pos, loff_t length,
        struct page *page = data;
        int ret;
 
-       ret = __block_write_begin_int(page, pos & ~PAGE_MASK, length,
-                       NULL, iomap);
+       ret = __block_write_begin_int(page, pos, length, NULL, iomap);
        if (ret)
                return ret;