[PATCH 09/14] libfuse: add FUSE_IOMAP_DIRECTIO

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

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@kernel.org>
---
 include/fuse_common.h |    7 +++++++
 include/fuse_kernel.h |    5 +++++
 lib/fuse_lowlevel.c   |    9 +++++++++
 3 files changed, 21 insertions(+)


diff --git a/include/fuse_common.h b/include/fuse_common.h
index 11eb22d011896c..657256b6309284 100644
--- a/include/fuse_common.h
+++ b/include/fuse_common.h
@@ -525,6 +525,11 @@ struct fuse_loop_config_v1 {
  */
 #define FUSE_CAP_IOMAP (1ULL << 32)
 
+/**
+ * Client supports using iomap for direct I/O file operations
+ */
+#define FUSE_CAP_IOMAP_DIRECTIO (1ULL << 33)
+
 /**
  * Ioctl flags
  *
@@ -1212,6 +1217,8 @@ struct fuse_iomap {
 
 /* enable fsdax */
 #define FUSE_IFLAG_DAX			(1U << 0)
+/* use iomap for directio */
+#define FUSE_IFLAG_IOMAP_DIRECTIO	(1U << 1)
 
 #endif /* FUSE_USE_VERSION >= 318 */
 
diff --git a/include/fuse_kernel.h b/include/fuse_kernel.h
index a06c16243a7885..7205de018634b9 100644
--- a/include/fuse_kernel.h
+++ b/include/fuse_kernel.h
@@ -240,6 +240,7 @@
  *  - add FUSE_IOMAP and iomap_{begin,end,ioend} handlers for FIEMAP and
  *    SEEK_{DATA,HOLE} support
  *  - add FUSE_DEV_IOC_IOMAP_DEV_ADD to configure block devices for iomap
+ *  - add FUSE_IOMAP_DIRECTIO/FUSE_ATTR_IOMAP_DIRECTIO for direct I/O support
  */
 
 #ifndef _LINUX_FUSE_H
@@ -450,6 +451,7 @@ struct fuse_file_lock {
  *			 init_out.request_timeout contains the timeout (in secs)
  * FUSE_IOMAP: Client supports iomap for FIEMAP and SEEK_{DATA,HOLE} file
  *	       operations.
+ * FUSE_IOMAP_DIRECTIO: Client supports iomap for direct I/O operations.
  */
 #define FUSE_ASYNC_READ		(1 << 0)
 #define FUSE_POSIX_LOCKS	(1 << 1)
@@ -498,6 +500,7 @@ struct fuse_file_lock {
 #define FUSE_OVER_IO_URING	(1ULL << 41)
 #define FUSE_REQUEST_TIMEOUT	(1ULL << 42)
 #define FUSE_IOMAP		(1ULL << 43)
+#define FUSE_IOMAP_DIRECTIO	(1ULL << 44)
 
 /**
  * CUSE INIT request/reply flags
@@ -581,9 +584,11 @@ 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_DIRECTIO: Use iomap for directio
  */
 #define FUSE_ATTR_SUBMOUNT      (1 << 0)
 #define FUSE_ATTR_DAX		(1 << 1)
+#define FUSE_ATTR_IOMAP_DIRECTIO	(1 << 2)
 
 /**
  * Open flags
diff --git a/lib/fuse_lowlevel.c b/lib/fuse_lowlevel.c
index 568db13502a7d7..f98900c51d4a9b 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_DIRECTIO)
+		attr->flags |= FUSE_ATTR_IOMAP_DIRECTIO;
 }
 
 static void convert_attr(const struct fuse_setattr_in *attr, struct stat *stbuf)
@@ -2777,6 +2779,8 @@ _do_init(fuse_req_t req, const fuse_ino_t nodeid, const void *op_in,
 			se->conn.capable_ext |= FUSE_CAP_OVER_IO_URING;
 		if (inargflags & FUSE_IOMAP)
 			se->conn.capable_ext |= FUSE_CAP_IOMAP;
+		if (inargflags & FUSE_IOMAP_DIRECTIO)
+			se->conn.capable_ext |= FUSE_CAP_IOMAP_DIRECTIO;
 	} else {
 		se->conn.max_readahead = 0;
 	}
@@ -2824,6 +2828,7 @@ _do_init(fuse_req_t req, const fuse_ino_t nodeid, const void *op_in,
 
 	/* servers need to opt-in to iomap explicitly */
 	LL_SET_DEFAULT(0, FUSE_CAP_IOMAP);
+	LL_SET_DEFAULT(0, FUSE_CAP_IOMAP_DIRECTIO);
 
 	/* This could safely become default, but libfuse needs an API extension
 	 * to support it
@@ -2945,6 +2950,8 @@ _do_init(fuse_req_t req, const fuse_ino_t nodeid, const void *op_in,
 	}
 	if (se->conn.want_ext & FUSE_CAP_IOMAP)
 		outargflags |= FUSE_IOMAP;
+	if (se->conn.want_ext & FUSE_CAP_IOMAP_DIRECTIO)
+		outargflags |= FUSE_IOMAP_DIRECTIO;
 
 	if (inargflags & FUSE_INIT_EXT) {
 		outargflags |= FUSE_INIT_EXT;
@@ -2988,6 +2995,8 @@ _do_init(fuse_req_t req, const fuse_ino_t nodeid, const void *op_in,
 				outarg.max_stack_depth);
 		if (se->conn.want_ext & FUSE_CAP_IOMAP)
 			fuse_log(FUSE_LOG_DEBUG, "   iomap=1\n");
+		if (se->conn.want_ext & FUSE_CAP_IOMAP_DIRECTIO)
+			fuse_log(FUSE_LOG_DEBUG, "   iomap_directio=1\n");
 	}
 	if (arg->minor < 5)
 		outargsize = FUSE_COMPAT_INIT_OUT_SIZE;