[PATCH 02/21] libfuse: add kernel gates for FUSE_IOMAP

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

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

Add some flags to query and request kernel support for filesystem iomap
for regular files.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
 include/fuse_common.h |    5 +++++
 include/fuse_kernel.h |    5 +++++
 lib/fuse_lowlevel.c   |   10 +++++++++-
 3 files changed, 19 insertions(+), 1 deletion(-)


diff --git a/include/fuse_common.h b/include/fuse_common.h
index b82f2c41deb30c..8f87263d78f999 100644
--- a/include/fuse_common.h
+++ b/include/fuse_common.h
@@ -520,6 +520,11 @@ struct fuse_loop_config_v1 {
  */
 #define FUSE_CAP_OVER_IO_URING (1UL << 31)
 
+/**
+ * Client supports using iomap for FIEMAP and SEEK_{DATA,HOLE}
+ */
+#define FUSE_CAP_IOMAP (1ULL << 32)
+
 /**
  * Ioctl flags
  *
diff --git a/include/fuse_kernel.h b/include/fuse_kernel.h
index 4d68c4e8a71d5f..6779b9c69bb9e2 100644
--- a/include/fuse_kernel.h
+++ b/include/fuse_kernel.h
@@ -237,6 +237,8 @@
  *  - add FUSE_NOTIFY_INC_EPOCH
  *
  *  7.99
+ *  - add FUSE_IOMAP and iomap_{begin,end,ioend} handlers for FIEMAP and
+ *    SEEK_{DATA,HOLE}
  */
 
 #ifndef _LINUX_FUSE_H
@@ -445,6 +447,8 @@ struct fuse_file_lock {
  * FUSE_OVER_IO_URING: Indicate that client supports io-uring
  * 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.
  */
 #define FUSE_ASYNC_READ		(1 << 0)
 #define FUSE_POSIX_LOCKS	(1 << 1)
@@ -492,6 +496,7 @@ struct fuse_file_lock {
 #define FUSE_ALLOW_IDMAP	(1ULL << 40)
 #define FUSE_OVER_IO_URING	(1ULL << 41)
 #define FUSE_REQUEST_TIMEOUT	(1ULL << 42)
+#define FUSE_IOMAP		(1ULL << 43)
 
 /**
  * CUSE INIT request/reply flags
diff --git a/lib/fuse_lowlevel.c b/lib/fuse_lowlevel.c
index 6afcecd3bdda96..33c71ba216679c 100644
--- a/lib/fuse_lowlevel.c
+++ b/lib/fuse_lowlevel.c
@@ -2686,7 +2686,8 @@ _do_init(fuse_req_t req, const fuse_ino_t nodeid, const void *op_in,
 			se->conn.capable_ext |= FUSE_CAP_NO_EXPORT_SUPPORT;
 		if (inargflags & FUSE_OVER_IO_URING)
 			se->conn.capable_ext |= FUSE_CAP_OVER_IO_URING;
-
+		if (inargflags & FUSE_IOMAP)
+			se->conn.capable_ext |= FUSE_CAP_IOMAP;
 	} else {
 		se->conn.max_readahead = 0;
 	}
@@ -2732,6 +2733,9 @@ _do_init(fuse_req_t req, const fuse_ino_t nodeid, const void *op_in,
 		       FUSE_CAP_READDIRPLUS_AUTO);
 	LL_SET_DEFAULT(1, FUSE_CAP_OVER_IO_URING);
 
+	/* servers need to opt-in to iomap explicitly */
+	LL_SET_DEFAULT(0, FUSE_CAP_IOMAP);
+
 	/* This could safely become default, but libfuse needs an API extension
 	 * to support it
 	 * LL_SET_DEFAULT(1, FUSE_CAP_SETXATTR_EXT);
@@ -2850,6 +2854,8 @@ _do_init(fuse_req_t req, const fuse_ino_t nodeid, const void *op_in,
 		outargflags |= FUSE_REQUEST_TIMEOUT;
 		outarg.request_timeout = se->conn.request_timeout;
 	}
+	if (se->conn.want_ext & FUSE_CAP_IOMAP)
+		outargflags |= FUSE_IOMAP;
 
 	if (inargflags & FUSE_INIT_EXT) {
 		outargflags |= FUSE_INIT_EXT;
@@ -2891,6 +2897,8 @@ _do_init(fuse_req_t req, const fuse_ino_t nodeid, const void *op_in,
 		if (se->conn.want_ext & FUSE_CAP_PASSTHROUGH)
 			fuse_log(FUSE_LOG_DEBUG, "   max_stack_depth=%u\n",
 				outarg.max_stack_depth);
+		if (se->conn.want_ext & FUSE_CAP_IOMAP)
+			fuse_log(FUSE_LOG_DEBUG, "   iomap=1\n");
 	}
 	if (arg->minor < 5)
 		outargsize = FUSE_COMPAT_INIT_OUT_SIZE;