[PATCH 11/21] libfuse: support direct I/O through iomap

["Darrick J. Wong" <djwong@xxxxxxxxxx>]

From: Darrick J. Wong <djwong@xxxxxxxxxx>

Make it so that fuse servers can ask the kernel fuse driver to use iomap
to support direct IO.

Signed-off-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
---
 include/fuse_common.h |    2 ++
 include/fuse_kernel.h |    7 +++++--
 lib/fuse_lowlevel.c   |    2 ++
 3 files changed, 9 insertions(+), 2 deletions(-)


diff --git a/include/fuse_common.h b/include/fuse_common.h
index 9181ec6cb5e5e9..6e8b2958373258 100644
--- a/include/fuse_common.h
+++ b/include/fuse_common.h
@@ -1228,6 +1228,8 @@ static inline bool fuse_iomap_need_write_allocate(unsigned int opflags,
 
 /* enable fsdax */
 #define FUSE_IFLAG_DAX			(1U << 0)
+/* use iomap for this inode */
+#define FUSE_IFLAG_IOMAP		(1U << 1)
 
 /* ----------------------------------------------------------- *
  * Compatibility stuff					       *
diff --git a/include/fuse_kernel.h b/include/fuse_kernel.h
index 849238c17baf5e..86c81871ca2b37 100644
--- a/include/fuse_kernel.h
+++ b/include/fuse_kernel.h
@@ -238,7 +238,8 @@
  *
  *  7.99
  *  - add FUSE_IOMAP and iomap_{begin,end,ioend} handlers for FIEMAP and
- *    SEEK_{DATA,HOLE}
+ *    SEEK_{DATA,HOLE}, and direct I/O
+ *  - add FUSE_ATTR_IOMAP to enable iomap for specific inodes
  */
 
 #ifndef _LINUX_FUSE_H
@@ -448,7 +449,7 @@ struct fuse_file_lock {
  * FUSE_REQUEST_TIMEOUT: kernel supports timing out requests.
  *			 init_out.request_timeout contains the timeout (in secs)
  * FUSE_IOMAP: Client supports iomap for FIEMAP and SEEK_{DATA,HOLE} file
- *	       operations.
+ *	       operations and direct I/O.
  */
 #define FUSE_ASYNC_READ		(1 << 0)
 #define FUSE_POSIX_LOCKS	(1 << 1)
@@ -580,9 +581,11 @@ struct fuse_file_lock {
  *
  * FUSE_ATTR_SUBMOUNT: Object is a submount root
  * FUSE_ATTR_DAX: Enable DAX for this file in per inode DAX mode
+ * FUSE_ATTR_IOMAP: Use iomap for this inode
  */
 #define FUSE_ATTR_SUBMOUNT      (1 << 0)
 #define FUSE_ATTR_DAX		(1 << 1)
+#define FUSE_ATTR_IOMAP		(1 << 2)
 
 /**
  * Open flags
diff --git a/lib/fuse_lowlevel.c b/lib/fuse_lowlevel.c
index 04bc858f54d01f..6a96c0f62d5884 100644
--- a/lib/fuse_lowlevel.c
+++ b/lib/fuse_lowlevel.c
@@ -124,6 +124,8 @@ static void convert_stat(const struct stat *stbuf, struct fuse_attr *attr,
 	attr->flags	= 0;
 	if (iflags & FUSE_IFLAG_DAX)
 		attr->flags |= FUSE_ATTR_DAX;
+	if (iflags & FUSE_IFLAG_IOMAP)
+		attr->flags |= FUSE_ATTR_IOMAP;
 }
 
 static void convert_attr(const struct fuse_setattr_in *attr, struct stat *stbuf)