1 files changed, 14 insertions, 11 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index d9f5336552d7..ad7242043bdb 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1695,8 +1695,7 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
         loff_t *ppos = &iocb->ki_pos;
         loff_t pos = *ppos;
 
-        /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
-        if (file->f_flags & O_DIRECT) {
+        if (io_is_direct(file)) {
                 struct address_space *mapping = file->f_mapping;
                 struct inode *inode = mapping->host;
                 size_t count = iov_iter_count(iter);
@@ -1723,9 +1722,11 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
                  * we've already read everything we wanted to, or if
                  * there was a short read because we hit EOF, go ahead
                  * and return.  Otherwise fallthrough to buffered io for
-                 * the rest of the read.
+                 * 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) || *ppos >= size) {
+                if (retval < 0 || !iov_iter_count(iter) || *ppos >= size ||
+                    IS_DAX(inode)) {
                         file_accessed(file);
                         goto out;
                 }
@@ -2582,18 +2583,20 @@ ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
         if (err)
                 goto out;
 
-        /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
-        if (unlikely(file->f_flags & O_DIRECT)) {
+        if (io_is_direct(file)) {
                 loff_t endbyte;
 
                 written = generic_file_direct_write(iocb, from, pos);
-                if (written < 0 || written == count)
-                        goto out;
-
                 /*
-                 * direct-io write to a hole: fall through to buffered I/O
-                 * for completing the rest of the request.
+                 * If the write stopped short of completing, fall back to
+                 * buffered writes.  Some filesystems do this for writes to
+                 * holes, for example.  For DAX files, a buffered write will
+                 * not succeed (even if it did, DAX does not handle dirty
+                 * page-cache pages correctly).
                  */
+                if (written < 0 || written == count || IS_DAX(inode))
+                        goto out;
+
                 pos += written;
                 count -= written;