[PATCH 2/2] dax: assert that i_rwsem is held exclusive for writes

Christoph Hellwig
2017-01-10T15:48:08Z

Make sure all callers follow the same locking protocol, given that DAX
transparantly replaced the normal buffered I/O path.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/dax.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/dax.c b/fs/dax.c
index 5c74f60..04734da 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1061,8 +1061,12 @@ dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
loff_t pos = iocb->ki_pos, ret = 0, done = 0;
unsigned flags = 0;

- if (iov_iter_rw(iter) == WRITE)
+ if (iov_iter_rw(iter) == WRITE) {
+ lockdep_assert_held_exclusive(&inode->i_rwsem);
flags |= IOMAP_WRITE;
+ } else {
+ lockdep_assert_held(&inode->i_rwsem);
+ }

while (iov_iter_count(iter)) {
ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
--
2.1.4