uapi nbd: improve doc links to userspace spec

The uapi <linux/nbd.h> header intentionally documents only the NBD server features that the kernel module will utilize as a client. But while it already had one mention of skipped bits due to userspace extensions, it did not actually direct the reader to the canonical source to learn about those extensions. While touching comments, fix an outdated reference that listed only READ and WRITE as commands.

Eric Blake committed 3 years ago

Commit daf376a1 parent ff53cd51 file · +12 −3Browse files

Showing the changes to include/uapi (1 of 1 file). Show all

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include/uapi/linux/nbd.h+12−3

@@ -11,6 +11,8 @@ · 10 unmodified lines
11	11	* Cleanup PARANOIA usage & code.
12	12	* 2004/02/19 Paul Clements
13	13	* Removed PARANOIA, plus various cleanup and comments
	14	+ * 2023 Copyright Red Hat
	15	+ * Link to userspace extensions.
14	16	*/
15	17
16	18	#ifndef _UAPILINUX_NBD_H
@@ -30,12 +32,18 @@ · 13 unmodified lines
30	32	#define NBD_SET_TIMEOUT _IO( 0xab, 9 )
31	33	#define NBD_SET_FLAGS _IO( 0xab, 10)
32	34
	35	+/*
	36	+ * See also https://github.com/NetworkBlockDevice/nbd/blob/master/doc/proto.md
	37	+ * for additional userspace extensions not yet utilized in the kernel module.
	38	+ */
	39	+
33	40	enum {
34	41	NBD_CMD_READ = 0,
35	42	NBD_CMD_WRITE = 1,
36	43	NBD_CMD_DISC = 2,
37	44	NBD_CMD_FLUSH = 3,
38	45	NBD_CMD_TRIM = 4
	46	+ /* userspace defines additional extension commands */
39	47	};
40	48
41	49	/* values for flags field, these are server interaction specific. */
@@ -64,14 +72,15 @@ enum { · 22 unmodified lines
64	72	#define NBD_REQUEST_MAGIC 0x25609513
65	73	#define NBD_REPLY_MAGIC 0x67446698
66	74	/* Do not use magics: 0x12560953 0x96744668. */
	75	+/* magic 0x668e33ef for structured reply not supported by kernel yet */
67	76
68	77	/*
69	78	* This is the packet used for communication between client and
70	79	* server. All data are in network byte order.
71	80	*/
72	81	struct nbd_request {
73		− __be32 magic;
74		− __be32 type; /* == READ \|\| == WRITE */
	82	+ __be32 magic; /* NBD_REQUEST_MAGIC */
	83	+ __be32 type; /* See NBD_CMD_* */
75	84	char handle[8];
76	85	__be64 from;
77	86	__be32 len;
@@ -82,7 +91,7 @@ struct nbd_request { · 4 unmodified lines
82	91	* it has completed an I/O request (or an error occurs).
83	92	*/
84	93	struct nbd_reply {
85		− __be32 magic;
	94	+ __be32 magic; /* NBD_REPLY_MAGIC */
86	95	__be32 error; /* 0 = ok, else error */
87	96	char handle[8]; /* handle you got from request */
88	97	};