[PATCH] [tgt]: Add BSG v4 backstore support to usr/bs_sg.c

[Nicholas A. Bellinger]

From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>

Greetings Tomo and Boaz,

This patch adds initial support for the block layer implementation of the sg v4 interface
(BSG) -> STGT with a new struct backingstore_template bsg_bst sharing code with the
original sg_bst.  It adds for new function bs_bsg_cmd_submit() for incoming write I/O
and bs_bsg_cmd_complete() for polling read I/O using include/linux/bsg.h:struct sg_io_v4.

This patch also splits up bs_sg_open() to support both BSG and SG looking for the
path "/dev/bsg" in bs_sg_open(), and getting max_queue using SG_GET_COMMAND_Q and
calling SG_SET_RESERVED_SIZE (following the original bs_sg code in init_sg_device)

Also chk_bsg_device() currently using a hardcoded 254 major as def for BSG does not
appear in include/linux/major.h just yet..

So far this has been tested with STGT/iSCSI <-> BSG <-> TCM_Loop SPC-4 iSCSI Target
Port emulation and is able to mkfs, fsck and mount a filesystem from a TCM/IBLOCK
Linux LVM kernel level backstore

Signed-off-by: Nicholas A. Bellinger <nab@xxxxxxxxxxxxxxx>
---
 usr/bs_sg.c     |  177 +++++++++++++++++++++++++++++++++++++++++++++++++++---
 usr/scsi_cmnd.h |    7 ++
 2 files changed, 174 insertions(+), 10 deletions(-)

diff --git a/usr/bs_sg.c b/usr/bs_sg.c
index 2fcb0d2..69dab53 100644
--- a/usr/bs_sg.c
+++ b/usr/bs_sg.c
@@ -3,6 +3,9 @@
  *
  * Copyright (C) 2008 Alexander Nezhinsky <nezhinsky@xxxxxxxxx>
  *
+ * Added linux/block/bsg.c support using struct sg_io_v4.
+ * Copyright (C) 2010 Nicholas A. Bellinger <nab@xxxxxxxxxxxxxxx>
+ *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
  * published by the Free Software Foundation, version 2 of the
@@ -33,6 +36,7 @@
 #include <sys/stat.h>
 #include <sys/epoll.h>
 #include <scsi/sg.h>
+#include <linux/bsg.h>
 
 #include "list.h"
 #include "util.h"
@@ -42,6 +46,14 @@
 #define BS_SG_RESVD_SZ  (512 * 1024)
 #define BS_SG_TIMEOUT	2000
 
+//#define BSG_DEBUG_IO
+
+#ifdef BSG_DEBUG_IO
+#define BSG_IO(x...) eprintf(x)
+#else
+#define BSG_IO(x...)
+#endif
+
 static int graceful_read(int fd, void *p_read, int to_read)
 {
 	int err;
@@ -82,7 +94,7 @@ static int graceful_write(int fd, void *p_write, int to_write)
 	return 0;
 }
 
-static void set_cmd_failed(struct scsi_cmd *cmd)
+static int set_cmd_failed(struct scsi_cmd *cmd)
 {
 	int result = SAM_STAT_CHECK_CONDITION;
 	uint16_t asc = ASC_READ_ERROR;
@@ -90,6 +102,54 @@ static void set_cmd_failed(struct scsi_cmd *cmd)
 
 	scsi_set_result(cmd, result);
 	sense_data_build(cmd, key, asc);
+
+	return result;
+}
+
+static int bs_bsg_cmd_submit(struct scsi_cmd *cmd)
+{
+	struct scsi_lu *dev = cmd->dev;
+	int fd = dev->fd;
+	struct sg_io_v4 *io_hdr = &cmd->cmd_bsg_hdr;
+	int err = 0;
+	/*
+	 * Following linux/include/linux/bsg.h
+	 */
+	/* [i] 'Q' to differentiate from v3 */
+	io_hdr->guard = 'Q';
+	io_hdr->protocol = BSG_PROTOCOL_SCSI;
+	io_hdr->subprotocol = BSG_SUB_PROTOCOL_SCSI_CMD;
+	io_hdr->request_len = cmd->scb_len;
+	io_hdr->request = (unsigned long )cmd->scb;
+
+	if (scsi_get_data_dir(cmd) == DATA_WRITE) {
+		io_hdr->dout_xfer_len = scsi_get_out_length(cmd);
+		io_hdr->dout_xferp = (unsigned long)scsi_get_out_buffer(cmd);	
+	} else {
+		io_hdr->din_xfer_len = scsi_get_in_length(cmd);
+		io_hdr->din_xferp = (unsigned long)scsi_get_in_buffer(cmd);
+	}
+	io_hdr->max_response_len = sizeof(cmd->sense_buffer);
+	/* SCSI: (auto)sense data */
+	io_hdr->response = (unsigned long)cmd->sense_buffer;
+	/* Using the same 2000 millisecond timeout.. */
+	io_hdr->timeout = BS_SG_TIMEOUT;
+	/* [i->o] unused internally */
+	io_hdr->usr_ptr = (unsigned long)cmd;
+	BSG_IO("[%d] Set io_hdr->usr_ptr from cmd: %p\n", getpid(), cmd);
+	/* Bsg does Q_AT_HEAD by default */
+	io_hdr->flags |= BSG_FLAG_Q_AT_TAIL;
+	
+	BSG_IO("[%d] Calling graceful_write for CDB: 0x%02x\n", getpid(), cmd->scb[0]);
+	err = graceful_write(fd, &cmd->cmd_bsg_hdr, sizeof(struct sg_io_v4));
+	if (!err)
+		set_cmd_async(cmd);
+	else {
+		eprintf("failed to start cmd 0x%p\n", cmd);
+		return set_cmd_failed(cmd);
+	}
+
+	return 0;
 }
 
 static int bs_sg_cmd_submit(struct scsi_cmd *cmd)
@@ -107,11 +167,13 @@ static int bs_sg_cmd_submit(struct scsi_cmd *cmd)
 	if (scsi_get_data_dir(cmd) == DATA_WRITE) {
 		io_hdr.dxfer_direction = SG_DXFER_TO_DEV;
 		io_hdr.dxfer_len = scsi_get_out_length(cmd);
-		io_hdr.dxferp = (void *)scsi_get_out_buffer(cmd);
+		cmd->cmd_sg_iovec.iov_base = scsi_get_out_buffer(cmd);
+		io_hdr.iovec_count = 1;
 	} else {
 		io_hdr.dxfer_direction = SG_DXFER_FROM_DEV;
 		io_hdr.dxfer_len = scsi_get_in_length(cmd);
-		io_hdr.dxferp = (void *)scsi_get_in_buffer(cmd);
+		cmd->cmd_sg_iovec.iov_base = scsi_get_in_buffer(cmd);
+		io_hdr.iovec_count = 1;
 	}
 	io_hdr.mx_sb_len = sizeof(cmd->sense_buffer);
 	io_hdr.sbp = cmd->sense_buffer;
@@ -125,11 +187,47 @@ static int bs_sg_cmd_submit(struct scsi_cmd *cmd)
 		set_cmd_async(cmd);
 	else {
 		eprintf("failed to start cmd 0x%p\n", cmd);
-		set_cmd_failed(cmd);
+		return set_cmd_failed(cmd);
 	}
 	return 0;
 }
 
+static void bs_bsg_cmd_complete(int fd, int events, void *data)
+{
+	struct sg_io_v4 io_hdr;
+	struct scsi_cmd *cmd;
+	int err;
+
+	BSG_IO("[%d] bs_bsg_cmd_complete() called!\n", getpid());
+	memset(&io_hdr, 0, sizeof(io_hdr));
+	/* [i] 'Q' to differentiate from v3 */
+	io_hdr.guard = 'Q';
+
+	err = graceful_read(fd, &io_hdr, sizeof(io_hdr));
+	if (err)
+		return;
+
+	cmd = (struct scsi_cmd *)(unsigned long)io_hdr.usr_ptr;
+	BSG_IO("BSG Using cmd: %p for io_hdr.usr_ptr\n", cmd);
+	/*
+	 * Check SCSI: command completion status
+	 * */
+	if (!io_hdr.device_status) {
+		scsi_set_out_resid(cmd, io_hdr.dout_resid);
+		scsi_set_in_resid(cmd, io_hdr.din_resid);
+	} else {
+		/*
+		 * NAB: Used by linux/block/bsg.c:bsg_ioctl(), is this
+		 * right..?
+		 */
+		cmd->sense_len = SCSI_SENSE_BUFFERSIZE;
+		scsi_set_out_resid_by_actual(cmd, 0);
+		scsi_set_in_resid_by_actual(cmd, 0);
+	}
+	BSG_IO("[%d] BSG() Calling cmd->scsi_cmd_done()\n", getpid());
+	cmd->scsi_cmd_done(cmd, io_hdr.device_status);
+}
+
 static void bs_sg_cmd_complete(int fd, int events, void *data)
 {
 	struct sg_io_hdr io_hdr;
@@ -157,6 +255,22 @@ static void bs_sg_cmd_complete(int fd, int events, void *data)
 	cmd->scsi_cmd_done(cmd, io_hdr.status);
 }
 
+static int chk_bsg_device(char *path)
+{
+	struct stat st;
+
+	if (stat(path, &st) < 0) {
+		eprintf("stat() failed errno: %d\n", errno);
+		return -1;
+	}
+
+	/* This is not yet defined in include/linux/major.h.. */
+	if (S_ISCHR(st.st_mode) && major(st.st_rdev) == 254)	
+		return 0;
+
+	return -1;
+}
+
 static int chk_sg_device(char *path)
 {
 	struct stat st;
@@ -168,8 +282,29 @@ static int chk_sg_device(char *path)
 
 	if (S_ISCHR(st.st_mode) && major(st.st_rdev) == SCSI_GENERIC_MAJOR)
 		return 0;
-	else
+
+	return -1;
+}
+
+static int init_bsg_device(int fd)
+{
+	int t, err;
+
+	err = ioctl(fd, SG_GET_COMMAND_Q, &t);
+	if (err < 0) {	
+		eprintf("SG_GET_COMMAND_Q for bsd failed: %d\n", err);
 		return -1;
+	}
+	eprintf("bsg: Using max_queue: %d\n", t);
+
+	t = BS_SG_RESVD_SZ;
+	err = ioctl(fd, SG_SET_RESERVED_SIZE, &t);
+	if (err < 0) {
+		eprintf("SG_SET_RESERVED_SIZE errno: %d\n", errno);
+		return -1;
+	}
+
+	return 0;
 }
 
 static int init_sg_device(int fd)
@@ -213,9 +348,14 @@ static int bs_sg_init(struct scsi_lu *lu)
 
 static int bs_sg_open(struct scsi_lu *lu, char *path, int *fd, uint64_t *size)
 {
-	int sg_fd, err;
-
-	err = chk_sg_device(path);
+	void (*cmd_complete)(int, int, void *) = NULL;
+	int sg_fd, err, bsg = 0;
+
+	if ((strstr(path, "/dev/bsg/") != NULL)) {
+		bsg = 1;
+		err = chk_bsg_device(path);
+	} else
+		err = chk_sg_device(path);
 	if (err) {
 		eprintf("Not recognized %s as an SG device\n", path);
 		return -EINVAL;
@@ -227,13 +367,19 @@ static int bs_sg_open(struct scsi_lu *lu, char *path, int *fd, uint64_t *size)
 		return sg_fd;
 	}
 
-	err = init_sg_device(sg_fd);
+	if (bsg) {
+		cmd_complete = &bs_bsg_cmd_complete;
+		err = init_bsg_device(sg_fd);
+	} else {
+		cmd_complete = bs_sg_cmd_complete;
+		err = init_sg_device(sg_fd);
+	}
 	if (err) {
 		eprintf("Failed to initialize sg device %s\n", path);
 		return err;
 	}
 
-	err = tgt_event_add(sg_fd, EPOLLIN, bs_sg_cmd_complete, NULL);
+	err = tgt_event_add(sg_fd, EPOLLIN, cmd_complete, NULL);
 	if (err) {
 		eprintf("Failed to add sg device event %s\n", path);
 		return err;
@@ -264,7 +410,18 @@ static struct backingstore_template sg_bst = {
 	.bs_cmd_done		= bs_sg_cmd_done,
 };
 
+static struct backingstore_template bsg_bst = {
+	.bs_name		= "bsg",
+	.bs_datasize		= 0,
+	.bs_init		= bs_sg_init,
+	.bs_open		= bs_sg_open,
+	.bs_close		= bs_sg_close,
+	.bs_cmd_submit		= bs_bsg_cmd_submit,
+	.bs_cmd_done		= bs_sg_cmd_done,
+};
+
 __attribute__((constructor)) static void bs_sg_constructor(void)
 {
 	register_backingstore_template(&sg_bst);
+	register_backingstore_template(&bsg_bst);
 }
diff --git a/usr/scsi_cmnd.h b/usr/scsi_cmnd.h
index 011f3e6..67a46c3 100644
--- a/usr/scsi_cmnd.h
+++ b/usr/scsi_cmnd.h
@@ -17,6 +17,9 @@ struct scsi_data_buffer {
 	uint64_t buffer;
 };
 
+#include <scsi/sg.h>
+#include <linux/bsg.h>
+
 struct scsi_cmd {
 	struct target *c_target;
 	/* linked it_nexus->cmd_hash_list */
@@ -31,6 +34,10 @@ struct scsi_cmd {
 	enum data_direction data_dir;
 	struct scsi_data_buffer in_sdb;
 	struct scsi_data_buffer out_sdb;
+	/* Used for bs_sg.c:bs_bs_cmd_submit() */
+	struct sg_iovec cmd_sg_iovec;
+	/* used for bs_sg.c:bs_bsg_cmd_submit() */
+	struct sg_io_v4 cmd_bsg_hdr;
 
 	uint64_t cmd_itn_id;
 	uint64_t offset;
-- 
1.5.6.5

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