Adds a relay_kernel_read() used by logdev_relay in logdev-0.5.4.patch.


---
 include/linux/relay.h |    4 +++
 kernel/relay.c        |   54 ++++++++++++++++++++++++++++++++++++++------------
 2 files changed, 46 insertions(+), 12 deletions(-)

Index: linux-2.6.21.5-rt20/include/linux/relay.h
===================================================================
--- linux-2.6.21.5-rt20.orig/include/linux/relay.h	2007-07-11 10:09:49.000000000 +0200
+++ linux-2.6.21.5-rt20/include/linux/relay.h	2007-07-11 14:28:47.000000000 +0200
@@ -178,6 +178,10 @@ extern int relay_buf_full(struct rchan_b
 
 extern size_t relay_switch_subbuf(struct rchan_buf *buf,
 				  size_t length);
+extern ssize_t relay_kernel_read(char *buffer,
+				 size_t count,
+				 loff_t *ppos,
+				 struct rchan_buf *kbuf);
 
 /**
  *	relay_write - write data into the channel
Index: linux-2.6.21.5-rt20/kernel/relay.c
===================================================================
--- linux-2.6.21.5-rt20.orig/kernel/relay.c	2007-07-11 10:09:49.000000000 +0200
+++ linux-2.6.21.5-rt20/kernel/relay.c	2007-07-11 14:28:47.000000000 +0200
@@ -946,14 +946,21 @@ static int subbuf_read_actor(size_t read
 			     struct rchan_buf *buf,
 			     size_t avail,
 			     read_descriptor_t *desc,
-			     read_actor_t actor)
+			     read_actor_t actor,
+			     int kernel_reader)
 {
 	void *from;
 	int ret = 0;
+	int err = 0;
 
 	from = buf->start + read_start;
 	ret = avail;
-	if (copy_to_user(desc->arg.buf, from, avail)) {
+
+	if (kernel_reader)
+		memcpy(desc->arg.buf, from, avail);
+	else
+		err = copy_to_user(desc->arg.buf, from, avail);
+	if (err) {
 		desc->error = -EFAULT;
 		ret = 0;
 	}
@@ -971,7 +978,8 @@ static int subbuf_send_actor(size_t read
 			     struct rchan_buf *buf,
 			     size_t avail,
 			     read_descriptor_t *desc,
-			     read_actor_t actor)
+			     read_actor_t actor,
+			     int kernel_reader)
 {
 	unsigned long pidx, poff;
 	unsigned int subbuf_pages;
@@ -1005,7 +1013,8 @@ typedef int (*subbuf_actor_t) (size_t re
 			       struct rchan_buf *buf,
 			       size_t avail,
 			       read_descriptor_t *desc,
-			       read_actor_t actor);
+			       read_actor_t actor,
+			       int kernel_reader);
 
 /*
  *	relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
@@ -1013,16 +1022,21 @@ typedef int (*subbuf_actor_t) (size_t re
 static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
 					subbuf_actor_t subbuf_actor,
 					read_actor_t actor,
-					read_descriptor_t *desc)
+					read_descriptor_t *desc,
+					struct rchan_buf *kbuf)
 {
-	struct rchan_buf *buf = filp->private_data;
+	struct rchan_buf *buf;
 	size_t read_start, avail;
-	int ret;
+	int ret, kernel_reader;
+
+	buf = kbuf ? kbuf : filp->private_data;
+	kernel_reader = filp ? 0 : 1;
 
 	if (!desc->count)
 		return 0;
 
-	mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
+	if (filp)
+		mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
 	do {
 		if (!relay_file_read_avail(buf, *ppos))
 			break;
@@ -1033,7 +1047,7 @@ static ssize_t relay_file_read_subbufs(s
 			break;
 
 		avail = min(desc->count, avail);
-		ret = subbuf_actor(read_start, buf, avail, desc, actor);
+		ret = subbuf_actor(read_start, buf, avail, desc, actor, kernel_reader);
 		if (desc->error < 0)
 			break;
 
@@ -1042,7 +1056,8 @@ static ssize_t relay_file_read_subbufs(s
 			*ppos = relay_file_read_end_pos(buf, read_start, ret);
 		}
 	} while (desc->count && ret);
-	mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
+	if (filp)
+		mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
 
 	return desc->written;
 }
@@ -1058,8 +1073,23 @@ static ssize_t relay_file_read(struct fi
 	desc.arg.buf = buffer;
 	desc.error = 0;
 	return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
-				       NULL, &desc);
+				       NULL, &desc, NULL);
+}
+
+ssize_t relay_kernel_read(char *buffer,
+			  size_t count,
+			  loff_t *ppos,
+			  struct rchan_buf *kbuf)
+{
+	read_descriptor_t desc;
+	desc.written = 0;
+	desc.count = count;
+	desc.arg.buf = buffer;
+	desc.error = 0;
+	return relay_file_read_subbufs(NULL, ppos, subbuf_read_actor,
+				       NULL, &desc, kbuf);
 }
+EXPORT_SYMBOL_GPL(relay_kernel_read);
 
 static ssize_t relay_file_sendfile(struct file *filp,
 				   loff_t *ppos,
@@ -1073,7 +1103,7 @@ static ssize_t relay_file_sendfile(struc
 	desc.arg.data = target;
 	desc.error = 0;
 	return relay_file_read_subbufs(filp, ppos, subbuf_send_actor,
-				       actor, &desc);
+				       actor, &desc, NULL);
 }
 
 const struct file_operations relay_file_operations = {