[PATCH 7/8] libfuse: add FUSE_IOMAP_PAGECACHE

["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 buffered IO.

Signed-off-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
---
 include/fuse_common.h |    5 +++++
 include/fuse_kernel.h |    3 +++
 lib/fuse_lowlevel.c   |    8 +++++++-
 3 files changed, 15 insertions(+), 1 deletion(-)


diff --git a/include/fuse_common.h b/include/fuse_common.h
index f7bc03427d12e4..a102e450944f4a 100644
--- a/include/fuse_common.h
+++ b/include/fuse_common.h
@@ -530,6 +530,11 @@ struct fuse_loop_config_v1 {
  */
 #define FUSE_CAP_IOMAP_DIRECTIO (1ULL << 33)
 
+/*
+ * Client supports using iomap for pagecache I/O file operations
+ */
+#define FUSE_CAP_IOMAP_PAGECACHE (1ULL << 34)
+
 /**
  * Ioctl flags
  *
diff --git a/include/fuse_kernel.h b/include/fuse_kernel.h
index a2c044b5957169..93ecb98a0bc20f 100644
--- a/include/fuse_kernel.h
+++ b/include/fuse_kernel.h
@@ -235,6 +235,7 @@
  *    SEEK_{DATA,HOLE} support
  *  - add FUSE_NOTIFY_ADD_IOMAP_DEVICE for multi-device filesystems
  *  - add FUSE_IOMAP_DIRECTIO for direct I/O support
+ *  - add FUSE_IOMAP_PAGECACHE for pagecache I/O support
  */
 
 #ifndef _LINUX_FUSE_H
@@ -444,6 +445,7 @@ struct fuse_file_lock {
  * FUSE_IOMAP: Client supports iomap for FIEMAP and SEEK_{DATA,HOLE} file
  *	       operations.
  * FUSE_IOMAP_DIRECTIO: Client supports iomap for direct I/O operations.
+ * FUSE_IOMAP_PAGECACHE: Client supports iomap for pagecache I/O operations.
  */
 #define FUSE_ASYNC_READ		(1 << 0)
 #define FUSE_POSIX_LOCKS	(1 << 1)
@@ -493,6 +495,7 @@ struct fuse_file_lock {
 #define FUSE_OVER_IO_URING	(1ULL << 41)
 #define FUSE_IOMAP		(1ULL << 43)
 #define FUSE_IOMAP_DIRECTIO	(1ULL << 44)
+#define FUSE_IOMAP_PAGECACHE	(1ULL << 45)
 
 /**
  * CUSE INIT request/reply flags
diff --git a/lib/fuse_lowlevel.c b/lib/fuse_lowlevel.c
index 9d07743fe522c6..fd12daf509cebf 100644
--- a/lib/fuse_lowlevel.c
+++ b/lib/fuse_lowlevel.c
@@ -2639,7 +2639,8 @@ _do_init(fuse_req_t req, const fuse_ino_t nodeid, const void *op_in,
 			se->conn.capable_ext |= FUSE_CAP_IOMAP;
 		if (inargflags & FUSE_IOMAP_DIRECTIO)
 			se->conn.capable_ext |= FUSE_CAP_IOMAP_DIRECTIO;
-
+		if (inargflags & FUSE_IOMAP_PAGECACHE)
+			se->conn.capable_ext |= FUSE_CAP_IOMAP_PAGECACHE;
 	} else {
 		se->conn.max_readahead = 0;
 	}
@@ -2688,6 +2689,7 @@ _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);
+	LL_SET_DEFAULT(0, FUSE_CAP_IOMAP_PAGECACHE);
 
 	/* This could safely become default, but libfuse needs an API extension
 	 * to support it
@@ -2816,6 +2818,8 @@ _do_init(fuse_req_t req, const fuse_ino_t nodeid, const void *op_in,
 		outargflags |= FUSE_IOMAP;
 	if (se->conn.want_ext & FUSE_CAP_IOMAP_DIRECTIO)
 		outargflags |= FUSE_IOMAP_DIRECTIO;
+	if (se->conn.want_ext & FUSE_CAP_IOMAP_PAGECACHE)
+		outargflags |= FUSE_IOMAP_PAGECACHE;
 
 	if (inargflags & FUSE_INIT_EXT) {
 		outargflags |= FUSE_INIT_EXT;
@@ -2861,6 +2865,8 @@ _do_init(fuse_req_t req, const fuse_ino_t nodeid, const void *op_in,
 			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 (se->conn.want_ext & FUSE_CAP_IOMAP_PAGECACHE)
+			fuse_log(FUSE_LOG_DEBUG, "   iomap_pagecache=1\n");
 	}
 	if (arg->minor < 5)
 		outargsize = FUSE_COMPAT_INIT_OUT_SIZE;