generic_file_read_iter(): make use of iov_iter_revert()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/mm/filemap.c b/mm/filemap.c
index 9f788eecd2c53b99af0a45cddde42a6d335fb4c6..cc480c07c71bad5b838e26f194e1d5b3e466e00f 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2033,7 +2033,6 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
        if (iocb->ki_flags & IOCB_DIRECT) {
                struct address_space *mapping = file->f_mapping;
                struct inode *inode = mapping->host;
-               struct iov_iter data = *iter;
                loff_t size;
 
                size = i_size_read(inode);
@@ -2044,11 +2043,12 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 
                file_accessed(file);
 
-               retval = mapping->a_ops->direct_IO(iocb, &data);
+               retval = mapping->a_ops->direct_IO(iocb, iter);
                if (retval >= 0) {
                        iocb->ki_pos += retval;
-                       iov_iter_advance(iter, retval);
+                       count -= retval;
                }
+               iov_iter_revert(iter, iov_iter_count(iter) - count);
 
                /*
                 * Btrfs can have a short DIO read if we encounter
@@ -2059,7 +2059,7 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
                 * the rest of the read.  Buffered reads will not work for
                 * DAX files, so don't bother trying.
                 */
-               if (retval < 0 || !iov_iter_count(iter) || iocb->ki_pos >= size ||
+               if (retval < 0 || !count || iocb->ki_pos >= size ||
                    IS_DAX(inode))
                        goto out;
        }