ADD file via upload

kernel/blk_drv/ll_rw_blk.c

@@ -0,0 +1,165 @@
+/*
+ *  linux/kernel/blk_dev/ll_rw.c
+ *
+ * (C) 1991 Linus Torvalds
+ */
+
+/*
+ * This handles all read/write requests to block devices
+ */
+#include <errno.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <asm/system.h>
+
+#include "blk.h"
+
+/*
+ * The request-struct contains all necessary data
+ * to load a nr of sectors into memory
+ */
+struct request request[NR_REQUEST];
+
+/*
+ * used to wait on when there are no free requests
+ */
+struct task_struct * wait_for_request = NULL;
+
+/* blk_dev_struct is:
+ *	do_request-address
+ *	next-request
+ */
+struct blk_dev_struct blk_dev[NR_BLK_DEV] = {
+	{ NULL, NULL },		/* no_dev */
+	{ NULL, NULL },		/* dev mem */
+	{ NULL, NULL },		/* dev fd */
+	{ NULL, NULL },		/* dev hd */
+	{ NULL, NULL },		/* dev ttyx */
+	{ NULL, NULL },		/* dev tty */
+	{ NULL, NULL }		/* dev lp */
+};
+
+static inline void lock_buffer(struct buffer_head * bh)
+{
+	cli();
+	while (bh->b_lock)
+		sleep_on(&bh->b_wait);
+	bh->b_lock=1;
+	sti();
+}
+
+static inline void unlock_buffer(struct buffer_head * bh)
+{
+	if (!bh->b_lock)
+		printk("ll_rw_block.c: buffer not locked\n\r");
+	bh->b_lock = 0;
+	wake_up(&bh->b_wait);
+}
+
+/*
+ * add-request adds a request to the linked list.
+ * It disables interrupts so that it can muck with the
+ * request-lists in peace.
+ */
+static void add_request(struct blk_dev_struct * dev, struct request * req)
+{
+	struct request * tmp;
+
+	req->next = NULL;
+	cli();
+	if (req->bh)
+		req->bh->b_dirt = 0;
+	if (!(tmp = dev->current_request)) {
+		dev->current_request = req;
+		sti();
+		(dev->request_fn)();
+		return;
+	}
+	for ( ; tmp->next ; tmp=tmp->next)
+		if ((IN_ORDER(tmp,req) ||
+		    !IN_ORDER(tmp,tmp->next)) &&
+		    IN_ORDER(req,tmp->next))
+			break;
+	req->next=tmp->next;
+	tmp->next=req;
+	sti();
+}
+
+static void make_request(int major,int rw, struct buffer_head * bh)
+{
+	struct request * req;
+	int rw_ahead;
+
+/* WRITEA/READA is special case - it is not really needed, so if the */
+/* buffer is locked, we just forget about it, else it's a normal read */
+	if (rw_ahead = (rw == READA || rw == WRITEA)) {
+		if (bh->b_lock)
+			return;
+		if (rw == READA)
+			rw = READ;
+		else
+			rw = WRITE;
+	}
+	if (rw!=READ && rw!=WRITE)
+		panic("Bad block dev command, must be R/W/RA/WA");
+	lock_buffer(bh);
+	if ((rw == WRITE && !bh->b_dirt) || (rw == READ && bh->b_uptodate)) {
+		unlock_buffer(bh);
+		return;
+	}
+repeat:
+/* we don't allow the write-requests to fill up the queue completely:
+ * we want some room for reads: they take precedence. The last third
+ * of the requests are only for reads.
+ */
+	if (rw == READ)
+		req = request+NR_REQUEST;
+	else
+		req = request+((NR_REQUEST*2)/3);
+/* find an empty request */
+	while (--req >= request)
+		if (req->dev<0)
+			break;
+/* if none found, sleep on new requests: check for rw_ahead */
+	if (req < request) {
+		if (rw_ahead) {
+			unlock_buffer(bh);
+			return;
+		}
+		sleep_on(&wait_for_request);
+		goto repeat;
+	}
+/* fill up the request-info, and add it to the queue */
+	req->dev = bh->b_dev;
+	req->cmd = rw;
+	req->errors=0;
+	req->sector = bh->b_blocknr<<1;
+	req->nr_sectors = 2;
+	req->buffer = bh->b_data;
+	req->waiting = NULL;
+	req->bh = bh;
+	req->next = NULL;
+	add_request(major+blk_dev,req);
+}
+
+void ll_rw_block(int rw, struct buffer_head * bh)
+{
+	unsigned int major;
+
+	if ((major=MAJOR(bh->b_dev)) >= NR_BLK_DEV ||
+	!(blk_dev[major].request_fn)) {
+		printk("Trying to read nonexistent block-device\n\r");
+		return;
+	}
+	make_request(major,rw,bh);
+}
+
+void blk_dev_init(void)
+{
+	int i;
+
+	for (i=0 ; i<NR_REQUEST ; i++) {
+		request[i].dev = -1;
+		request[i].next = NULL;
+	}
+}