[PATCH V3 2/4] fuse_kernel.h: add famfs DAX fmap protocol definitions

[John Groves <John@Groves.net>]

Add FUSE protocol version 7.46 definitions for famfs DAX file mapping:

Capability flag:
  - FUSE_DAX_FMAP (bit 43): kernel supports DAX fmap operations

New opcodes:
  - FUSE_GET_FMAP (54): retrieve file extent map for DAX mapping
  - FUSE_GET_DAXDEV (55): retrieve DAX device info by index

New structures for GET_FMAP reply:
  - struct fuse_famfs_fmap_header: file map header with type and extent info
  - struct fuse_famfs_simple_ext: simple extent (device, offset, length)
  - struct fuse_famfs_iext: interleaved extent for striped allocations

New structures for GET_DAXDEV:
  - struct fuse_get_daxdev_in: request DAX device by index
  - struct fuse_daxdev_out: DAX device name response

Supporting definitions:
  - enum fuse_famfs_file_type: regular, superblock, or log file
  - enum famfs_ext_type: simple or interleaved extent type

Signed-off-by: John Groves <john@groves.net>
---
 include/fuse_kernel.h | 88 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)

diff --git a/include/fuse_kernel.h b/include/fuse_kernel.h
index c13e1f9..7fdfc30 100644
--- a/include/fuse_kernel.h
+++ b/include/fuse_kernel.h
@@ -240,6 +240,19 @@
  *  - add FUSE_COPY_FILE_RANGE_64
  *  - add struct fuse_copy_file_range_out
  *  - add FUSE_NOTIFY_PRUNE
+ *
+ *  7.46
+ *    - Add FUSE_DAX_FMAP capability - ability to handle in-kernel fsdax maps
+ *    - Add the following structures for the GET_FMAP message reply components:
+ *      - struct fuse_famfs_simple_ext
+ *      - struct fuse_famfs_iext
+ *      - struct fuse_famfs_fmap_header
+ *    - Add the following structs for the GET_DAXDEV message and reply
+ *      - struct fuse_get_daxdev_in
+ *      - struct fuse_get_daxdev_out
+ *    - Add the following enumerated types
+ *      - enum fuse_famfs_file_type
+ *      - enum famfs_ext_type
  */
 
 #ifndef _LINUX_FUSE_H
@@ -448,6 +461,7 @@ 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_DAX_FMAP:        kernel supports dev_dax_iomap (aka famfs) fmaps
  */
 #define FUSE_ASYNC_READ		(1 << 0)
 #define FUSE_POSIX_LOCKS	(1 << 1)
@@ -495,6 +509,7 @@ 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_DAX_FMAP		(1ULL << 43)
 
 /**
  * CUSE INIT request/reply flags
@@ -664,6 +679,10 @@ enum fuse_opcode {
 	FUSE_STATX		= 52,
 	FUSE_COPY_FILE_RANGE_64	= 53,
 
+	/* Famfs / devdax opcodes */
+	FUSE_GET_FMAP           = 54,
+	FUSE_GET_DAXDEV         = 55,
+
 	/* CUSE specific operations */
 	CUSE_INIT		= 4096,
 
@@ -1308,4 +1327,73 @@ struct fuse_uring_cmd_req {
 	uint8_t padding[6];
 };
 
+/* Famfs fmap message components */
+
+#define FAMFS_FMAP_VERSION 1
+
+#define FAMFS_FMAP_MAX 32768 /* Largest supported fmap message */
+#define FUSE_FAMFS_MAX_EXTENTS 32
+#define FUSE_FAMFS_MAX_STRIPS 32
+
+enum fuse_famfs_file_type {
+	FUSE_FAMFS_FILE_REG,
+	FUSE_FAMFS_FILE_SUPERBLOCK,
+	FUSE_FAMFS_FILE_LOG,
+};
+
+enum famfs_ext_type {
+	FUSE_FAMFS_EXT_SIMPLE = 0,
+	FUSE_FAMFS_EXT_INTERLEAVE = 1,
+};
+
+struct fuse_famfs_simple_ext {
+	uint32_t se_devindex;
+	uint32_t reserved;
+	uint64_t se_offset;
+	uint64_t se_len;
+};
+
+struct fuse_famfs_iext { /* Interleaved extent */
+	uint32_t ie_nstrips;
+	uint32_t ie_chunk_size;
+	uint64_t ie_nbytes; /* Total bytes for this interleaved_ext;
+			     * sum of strips may be more
+			     */
+	uint64_t reserved;
+};
+
+struct fuse_famfs_fmap_header {
+	uint8_t file_type; /* enum famfs_file_type */
+	uint8_t reserved;
+	uint16_t fmap_version;
+	uint32_t ext_type; /* enum famfs_log_ext_type */
+	uint32_t nextents;
+	uint32_t reserved0;
+	uint64_t file_size;
+	uint64_t reserved1;
+};
+
+struct fuse_get_daxdev_in {
+	uint32_t        daxdev_num;
+};
+
+#define DAXDEV_NAME_MAX 256
+
+/* fuse_daxdev_out has enough space for a uuid if we need it */
+struct fuse_daxdev_out {
+	uint16_t index;
+	uint16_t reserved;
+	uint32_t reserved2;
+	uint64_t reserved3;
+	uint64_t reserved4;
+	char name[DAXDEV_NAME_MAX];
+};
+
+static __inline__ int32_t fmap_msg_min_size(void)
+{
+	/* Smallest fmap message is a header plus one simple extent */
+	return (sizeof(struct fuse_famfs_fmap_header)
+		+ sizeof(struct fuse_famfs_simple_ext));
+}
+
 #endif /* _LINUX_FUSE_H */
-- 
2.49.0