Fix build errors with linux kernel v3.19 and above

Below errors came up while building iscsitarget for 
qemux86-64 (and others) because,
1. 'struct user_msghdr' is being used for userland-side msghdr instead
of 'struct msghdr', which is used for kernel-side msghdr in linux v3.19
and above.

error snippet:
-- snip --
| /CGE7_SHDD/project_yocto_1.8/poky/build/tmp/work/qemux86_64-poky-linux/iscsitarget/1.4.20.3+svn502-r0/iscsitarget-1.4.20.3+svn502/kernel/iscsi.c: In function 'cmnd_skip_pdu':
| /CGE7_SHDD/project_yocto_1.8/poky/build/tmp/work/qemux86_64-poky-linux/iscsitarget/1.4.20.3+svn502-r0/iscsitarget-1.4.20.3+svn502/kernel/iscsi.c:492:16: error: 'struct msghdr' has no member named 'msg_iov'
|   conn->read_msg.msg_iov = conn->read_iov;
-- CUT --

Reference:
https://github.com/torvalds/linux/commit/666547ff591cebdedc4679bf6b1b3f3383a8dea3

2. 'SERVICE_ACTION_IN' has been renamed to SERVICE_ACTION_IN_16 in linux v3.19
and above.

error snippet:
-- snip --
| /CGE7_SHDD/project_yocto_1.8/poky/build/tmp/work/qemux86_64-poky-linux/iscsitarget/1.4.20.3+svn502-r0/iscsitarget-1.4.20.3+svn502/kernel/iscsi.c: In function 'scsi_cmnd_start':
| /CGE7_SHDD/project_yocto_1.8/poky/build/tmp/work/qemux86_64-poky-linux/iscsitarget/1.4.20.3+svn502-r0/iscsitarget-1.4.20.3+svn502/kernel/iscsi.c:989:7: error: 'SERVICE_ACTION_IN' undeclared (first use in this function)
|   case SERVICE_ACTION_IN:
-- CUT --

Reference:
https://github.com/torvalds/linux/commit/eb846d9f147455e4e5e1863bfb5e31974bb69b7c

3. In linux v3.19 and above, f_dentry member has been removed from 
'struct file' structure.

error snippet:
-- snip --
| /CGE7_SHDD/project_yocto_1.8/poky/build/tmp/work/qemux86_64-poky-linux/iscsitarget/1.4.20.3+svn502-r0/iscsitarget-1.4.20.3+svn502/kernel/conn.c: In function 'iet_socket_bind':
| /CGE7_SHDD/project_yocto_1.8/poky/build/tmp/work/qemux86_64-poky-linux/iscsitarget/1.4.20.3+svn502-r0/iscsitarget-1.4.20.3+svn502/kernel/conn.c:130:34: error: 'struct file' has no member named 'f_dentry'
|   conn->sock = SOCKET_I(conn->file->f_dentry->d_inode);
-- CUT --

new helper function file_inode(file) should be used instead.

References:
1. https://github.com/torvalds/linux/commit/78d28e651f97866d608d9b41f8ad291e65d47dd5
2. https://github.com/torvalds/linux/commit/496ad9aa8ef448058e36ca7a787c61f2e63f0f54

Upstream-Status: Pending

Signed-off-by: Jagadeesh Krishnanjanappa <jkrishnanjanappa@mvista.com>

--- iscsitarget-1.4.20.3+svn502_org/kernel/conn.c	2015-08-24 16:13:26.481924679 +0530
+++ iscsitarget-1.4.20.3+svn502/kernel/conn.c	2015-08-24 17:27:06.897653698 +0530
@@ -127,7 +127,11 @@ static void iet_socket_bind(struct iscsi
 
 	dprintk(D_GENERIC, "%llu\n", (unsigned long long) session->sid);
 
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0)
+	conn->sock = SOCKET_I(file_inode(conn->file));
+#else
 	conn->sock = SOCKET_I(conn->file->f_dentry->d_inode);
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0) */
 	conn->sock->sk->sk_user_data = conn;
 
 	write_lock_bh(&conn->sock->sk->sk_callback_lock);
--- iscsitarget-1.4.20.3+svn502_org/kernel/file-io.c	2015-08-24 16:13:26.481924679 +0530
+++ iscsitarget-1.4.20.3+svn502/kernel/file-io.c	2015-08-24 17:30:54.390131100 +0530
@@ -69,7 +69,11 @@ static int fileio_make_request(struct ie
 static int fileio_sync(struct iet_volume *lu, struct tio *tio)
 {
 	struct fileio_data *p = lu->private;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0)
+	struct inode *inode = file_inode(p->filp);
+#else
 	struct inode *inode = p->filp->f_dentry->d_inode;
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0) */
 	struct address_space *mapping = inode->i_mapping;
 	loff_t ppos, count;
 	int res;
@@ -213,7 +217,11 @@ static int fileio_attach(struct iet_volu
 		eprintk("%d\n", err);
 		goto out;
 	}
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0)
+	inode = file_inode(p->filp);
+#else
 	inode = p->filp->f_dentry->d_inode;
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0) */
 
 	if (S_ISREG(inode->i_mode))
 		;
--- iscsitarget-1.4.20.3+svn502_org/kernel/iscsi.c	2015-08-24 16:13:26.481924679 +0530
+++ iscsitarget-1.4.20.3+svn502/kernel/iscsi.c	2015-08-24 17:33:50.950490156 +0530
@@ -986,7 +986,11 @@ static void scsi_cmnd_start(struct iscsi
 		set_cmnd_lunit(req);
 
 	switch (req_hdr->scb[0]) {
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0)
+	case SERVICE_ACTION_IN_16:
+#else
 	case SERVICE_ACTION_IN:
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0) */
 		if ((req_hdr->scb[1] & 0x1f) != 0x10)
 			goto error;
 	case INQUIRY:
--- iscsitarget-1.4.20.3+svn502_org/kernel/iscsi.h	2015-08-24 16:13:26.481924679 +0530
+++ iscsitarget-1.4.20.3+svn502/kernel/iscsi.h	2015-08-24 17:35:31.354690051 +0530
@@ -257,7 +257,11 @@ struct iscsi_conn {
 	struct timer_list nop_timer;
 
 	struct iscsi_cmnd *read_cmnd;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0)
+	struct user_msghdr read_msg;
+#else
 	struct msghdr read_msg;
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0) */
 	struct iovec read_iov[ISCSI_CONN_IOV_MAX];
 	u32 read_size;
 	u32 read_overflow;
--- iscsitarget-1.4.20.3+svn502_org/kernel/nthread.c	2015-08-24 16:13:26.481924679 +0530
+++ iscsitarget-1.4.20.3+svn502/kernel/nthread.c	2015-08-24 17:41:56.187428925 +0530
@@ -80,8 +80,11 @@ static int is_data_available(struct iscs
 	set_fs(oldfs);
 	return (res >= 0) ? avail : res;
 }
-
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0)
+static void forward_iov(struct user_msghdr *msg, int len)
+#else
 static void forward_iov(struct msghdr *msg, int len)
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0) */
 {
 	while (msg->msg_iov->iov_len <= len) {
 		len -= msg->msg_iov->iov_len;
@@ -96,7 +99,11 @@ static void forward_iov(struct msghdr *m
 static int do_recv(struct iscsi_conn *conn, int state)
 {
 	mm_segment_t oldfs;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0)
+	struct user_msghdr msg;
+#else
 	struct msghdr msg;
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0) */
 	struct iovec iov[ISCSI_CONN_IOV_MAX];
 	int i, len, res;
 
@@ -461,7 +468,11 @@ static void exit_tx(struct iscsi_conn *c
 static int tx_ddigest(struct iscsi_cmnd *cmnd, int state)
 {
 	int res, rest = cmnd->conn->write_size;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0)
+	struct user_msghdr msg = {.msg_flags = MSG_NOSIGNAL | MSG_DONTWAIT};
+#else
 	struct msghdr msg = {.msg_flags = MSG_NOSIGNAL | MSG_DONTWAIT};
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0) */
 	struct kvec iov;
 
 	iov.iov_base = (char *) (&cmnd->ddigest) + (sizeof(u32) - rest);
--- iscsitarget-1.4.20.3+svn502_org/kernel/target_disk.c	2015-08-24 16:13:26.481924679 +0530
+++ iscsitarget-1.4.20.3+svn502/kernel/target_disk.c	2015-08-24 17:43:42.167625159 +0530
@@ -606,7 +606,11 @@ static int disk_execute_cmnd(struct iscs
 	case REQUEST_SENSE:
 		send_data_rsp(cmnd, build_request_sense_response);
 		break;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0)
+	case SERVICE_ACTION_IN_16:
+#else
 	case SERVICE_ACTION_IN:
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0) */	
 		send_data_rsp(cmnd, build_service_action_in_response);
 		break;
 	case READ_6:
--- iscsitarget-1.4.20.3+svn502_org/kernel/volume.c	2015-08-24 16:13:26.477924674 +0530
+++ iscsitarget-1.4.20.3+svn502/kernel/volume.c	2015-08-24 18:28:15.697074780 +0530
@@ -398,7 +398,11 @@ int is_volume_reserved(struct iet_volume
 		case READ_CAPACITY:
 			/* allowed commands when reserved */
 			break;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0)			
+		case SERVICE_ACTION_IN_16:
+#else
 		case SERVICE_ACTION_IN:
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0) */
 			if ((scb[1] & 0x1F) == 0x10)
 				break;
 			/* fall through */
@@ -465,7 +469,11 @@ int is_volume_reserved(struct iet_volume
 		if (excl_access_ro && !registered)
 			err = -EBUSY;
 		break;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0)
+	case SERVICE_ACTION_IN_16:
+#else
 	case SERVICE_ACTION_IN:
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(3, 19, 0) */
 		if ((scb[1] & 0x1F) == 0x10)
 			break;
 		/* fall through */