relay revamp 7, full patch

index 85049a7..19e417c 100644
@@ -35,7 +35,7 @@ static void trace_note(struct blk_trace *bt, pid_t pid, int action,
 {
 	struct blk_io_trace *t;
 
-	t = relay_reserve(bt->rchan, sizeof(*t) + len);
+	t = pagewriter_reserve(bt->pagewriter, sizeof(*t) + len);
 	if (t) {
 		const int cpu = smp_processor_id();
 

@@ -153,7 +153,7 @@ void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
 	if (unlikely(tsk->btrace_seq != blktrace_seq))
 		trace_note_tsk(bt, tsk);
 
-	t = relay_reserve(bt->rchan, sizeof(*t) + pdu_len);
+	t = pagewriter_reserve(bt->pagewriter, sizeof(*t) + pdu_len);
 	if (t) {
 		cpu = smp_processor_id();
 		sequence = per_cpu_ptr(bt->sequence, cpu);

@@ -230,7 +230,7 @@ err:
 
 static void blk_trace_cleanup(struct blk_trace *bt)
 {
-	relay_close(bt->rchan);
+	pagewriter_close(bt->pagewriter);
 	debugfs_remove(bt->msg_file);
 	debugfs_remove(bt->dropped_file);
 	blk_remove_tree(bt->dir);

@@ -268,7 +268,8 @@ static ssize_t blk_dropped_read(struct file *filp, char __user *buffer,
 	struct blk_trace *bt = filp->private_data;
 	char buf[16];
 
-	snprintf(buf, sizeof(buf), "%u\n", atomic_read(&bt->dropped));
+	snprintf(buf, sizeof(buf), "%u\n",
+		 atomic_read(&bt->pagewriter->dropped));
 
 	return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf));
 }

@@ -317,43 +318,19 @@ static const struct file_operations blk_msg_fops = {
 	.write =	blk_msg_write,
 };
 
-/*
- * Keep track of how many times we encountered a full subbuffer, to aid
- * the user space app in telling how many lost events there were.
- */
-static int blk_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
-				     void *prev_subbuf, size_t prev_padding)
+static void blk_write_padding_callback(struct pagewriter_buf *buf,
+				       size_t length,
+				       void *reserved)
 {
-	struct blk_trace *bt;
+	struct blk_io_trace *t = reserved;
 
-	if (!relay_buf_full(buf))
-		return 1;
-
-	bt = buf->chan->private_data;
-	atomic_inc(&bt->dropped);
-	return 0;
-}
-
-static int blk_remove_buf_file_callback(struct dentry *dentry)
-{
-	debugfs_remove(dentry);
-	return 0;
-}
-
-static struct dentry *blk_create_buf_file_callback(const char *filename,
-						   struct dentry *parent,
-						   int mode,
-						   struct rchan_buf *buf,
-						   int *is_global)
-{
-	return debugfs_create_file(filename, mode, parent, buf,
-					&relay_file_operations);
+	t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
+	t->action = BLK_TN_PADDING;
+	t->pdu_len = length - sizeof(*t);
 }
 
-static struct rchan_callbacks blk_relay_callbacks = {
-	.subbuf_start		= blk_subbuf_start_callback,
-	.create_buf_file	= blk_create_buf_file_callback,
-	.remove_buf_file	= blk_remove_buf_file_callback,
+static struct pagewriter_callbacks blk_pagewriter_callbacks = {
+	.write_padding           = blk_write_padding_callback,
 };
 
 /*

@@ -365,6 +342,7 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 	struct blk_trace *old_bt, *bt = NULL;
 	struct dentry *dir = NULL;
 	int ret, i;
+	int n_pages, n_pages_wakeup;
 
 	if (!buts->buf_size || !buts->buf_nr)
 		return -EINVAL;

@@ -400,7 +378,6 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 
 	bt->dir = dir;
 	bt->dev = dev;
-	atomic_set(&bt->dropped, 0);
 
 	ret = -EIO;
 	bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt, &blk_dropped_fops);

@@ -411,9 +388,13 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 	if (!bt->msg_file)
 		goto err;
 
-	bt->rchan = relay_open("trace", dir, buts->buf_size,
-				buts->buf_nr, &blk_relay_callbacks, bt);
-	if (!bt->rchan)
+	n_pages = (buts->buf_size * buts->buf_nr) / PAGE_SIZE;
+	n_pages_wakeup = buts->buf_size / PAGE_SIZE;
+	bt->pagewriter = pagewriter_open("trace", dir, n_pages, n_pages_wakeup,
+					 sizeof(struct blk_io_trace),
+					 &blk_pagewriter_callbacks, bt,
+					 PAGEWRITER_PAD_WRITES);
+	if (!bt->pagewriter)
 		goto err;
 
 	bt->act_mask = buts->act_mask;

@@ -446,8 +427,8 @@ err:
 			debugfs_remove(bt->dropped_file);
 		free_percpu(bt->sequence);
 		free_percpu(bt->msg_data);
-		if (bt->rchan)
-			relay_close(bt->rchan);
+		if (bt->pagewriter)
+			pagewriter_close(bt->pagewriter);
 		kfree(bt);
 	}
 	return ret;

@@ -500,7 +481,7 @@ int blk_trace_startstop(struct request_queue *q, int start)
 	} else {
 		if (bt->trace_state == Blktrace_running) {
 			bt->trace_state = Blktrace_stopped;
-			relay_flush(bt->rchan);
+			pagewriter_flush(bt->pagewriter);
 			ret = 0;
 		}
 	}

index bdf505d..b14e6e4 100644
@@ -3,7 +3,7 @@
 
 #ifdef __KERNEL__
 #include <linux/blkdev.h>
-#include <linux/relay.h>
+#include <linux/relay_pagewriter.h>
 #endif
 
 /*

@@ -62,6 +62,7 @@ enum blktrace_notify {
 	__BLK_TN_PROCESS = 0,		/* establish pid/name mapping */
 	__BLK_TN_TIMESTAMP,		/* include system clock */
 	__BLK_TN_MESSAGE,		/* Character string message */
+	__BLK_TN_PADDING,		/* Padding message */
 };
 
 

@@ -89,6 +90,7 @@ enum blktrace_notify {
 #define BLK_TN_PROCESS		(__BLK_TN_PROCESS | BLK_TC_ACT(BLK_TC_NOTIFY))
 #define BLK_TN_TIMESTAMP	(__BLK_TN_TIMESTAMP | BLK_TC_ACT(BLK_TC_NOTIFY))
 #define BLK_TN_MESSAGE		(__BLK_TN_MESSAGE | BLK_TC_ACT(BLK_TC_NOTIFY))
+#define BLK_TN_PADDING		(__BLK_TN_PADDING | BLK_TC_ACT(BLK_TC_NOTIFY))
 
 #define BLK_IO_TRACE_MAGIC	0x65617400
 #define BLK_IO_TRACE_VERSION	0x07

@@ -144,7 +146,7 @@ struct blk_user_trace_setup {
 #if defined(CONFIG_BLK_DEV_IO_TRACE)
 struct blk_trace {
 	int trace_state;
-	struct rchan *rchan;
+	struct pagewriter *pagewriter;
 	unsigned long *sequence;
 	unsigned char *msg_data;
 	u16 act_mask;

@@ -155,7 +157,6 @@ struct blk_trace {
 	struct dentry *dir;
 	struct dentry *dropped_file;
 	struct dentry *msg_file;
-	atomic_t dropped;
 };
 
 extern int blk_trace_ioctl(struct block_device *, unsigned, char __user *);

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