dax-assert-that-i_rw_sem-is-held-exclusive-for-writes

   1 dax: assert that i_rwsem is held exclusive for writes
   2
   3 From: Christoph Hellwig <hch@lst.de>
   4
   5 Make sure all callers follow the same locking protocol, given that DAX
   6 transparantly replaced the normal buffered I/O path.
   7
   8 Signed-off-by: Christoph Hellwig <hch@lst.de>
   9 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  10 Reviewed-by: Jan Kara <jack@suse.cz>
  11 ---
  12  fs/dax.c | 6 +++++-
  13  1 file changed, 5 insertions(+), 1 deletion(-)
  14
  15 diff --git a/fs/dax.c b/fs/dax.c
  16 index 5c74f60d0a50..04734daed1bd 100644
  17 --- a/fs/dax.c
  18 +++ b/fs/dax.c
  19 @@ -1061,8 +1061,12 @@ dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
  20         loff_t pos = iocb->ki_pos, ret = 0, done = 0;
  21         unsigned flags = 0;
  22
  23 -       if (iov_iter_rw(iter) == WRITE)
  24 +       if (iov_iter_rw(iter) == WRITE) {
  25 +               lockdep_assert_held_exclusive(&inode->i_rwsem);
  26                 flags |= IOMAP_WRITE;
  27 +       } else {
  28 +               lockdep_assert_held(&inode->i_rwsem);
  29 +       }
  30
  31         while (iov_iter_count(iter)) {
  32                 ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,