ADD file via upload

kernel/blk_drv/ramdisk.c

@@ -0,0 +1,126 @@
+/*
+ *  linux/kernel/blk_drv/ramdisk.c
+ *
+ *  Written by Theodore Ts'o, 12/2/91
+ */
+
+#include <string.h>
+
+#include <linux/config.h>
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/kernel.h>
+#include <asm/system.h>
+#include <asm/segment.h>
+#include <asm/memory.h>
+
+#define MAJOR_NR 1
+#include "blk.h"
+
+char	*rd_start;
+int	rd_length = 0;
+
+void do_rd_request(void)
+{
+	int	len;
+	char	*addr;
+
+	INIT_REQUEST;
+	addr = rd_start + (CURRENT->sector << 9);
+	len = CURRENT->nr_sectors << 9;
+	if ((MINOR(CURRENT->dev) != 1) || (addr+len > rd_start+rd_length)) {
+		end_request(0);
+		goto repeat;
+	}
+	if (CURRENT-> cmd == WRITE) {
+		(void ) memcpy(addr,
+			      CURRENT->buffer,
+			      len);
+	} else if (CURRENT->cmd == READ) {
+		(void) memcpy(CURRENT->buffer, 
+			      addr,
+			      len);
+	} else
+		panic("unknown ramdisk-command");
+	end_request(1);
+	goto repeat;
+}
+
+/*
+ * Returns amount of memory which needs to be reserved.
+ */
+long rd_init(long mem_start, int length)
+{
+	int	i;
+	char	*cp;
+
+	blk_dev[MAJOR_NR].request_fn = DEVICE_REQUEST;
+	rd_start = (char *) mem_start;
+	rd_length = length;
+	cp = rd_start;
+	for (i=0; i < length; i++)
+		*cp++ = '\0';
+	return(length);
+}
+
+/*
+ * If the root device is the ram disk, try to load it.
+ * In order to do this, the root device is originally set to the
+ * floppy, and we later change it to be ram disk.
+ */
+void rd_load(void)
+{
+	struct buffer_head *bh;
+	struct super_block	s;
+	int		block = 256;	/* Start at block 256 */
+	int		i = 1;
+	int		nblocks;
+	char		*cp;		/* Move pointer */
+	
+	if (!rd_length)
+		return;
+	printk("Ram disk: %d bytes, starting at 0x%x\n", rd_length,
+		(int) rd_start);
+	if (MAJOR(ROOT_DEV) != 2)
+		return;
+	bh = breada(ROOT_DEV,block+1,block,block+2,-1);
+	if (!bh) {
+		printk("Disk error while looking for ramdisk!\n");
+		return;
+	}
+	__asm__ volatile ("cld");   /* by wyj */
+	*((struct d_super_block *) &s) = *((struct d_super_block *) bh->b_data);
+	brelse(bh);
+	if (s.s_magic != SUPER_MAGIC)
+		/* No ram disk image present, assume normal floppy boot */
+		return;
+	nblocks = s.s_nzones << s.s_log_zone_size;
+	if (nblocks > (rd_length >> BLOCK_SIZE_BITS)) {
+		printk("Ram disk image too big!  (%d blocks, %d avail)\n", 
+			nblocks, rd_length >> BLOCK_SIZE_BITS);
+		return;
+	}
+	printk("Loading %d bytes into ram disk... 0000k", 
+		nblocks << BLOCK_SIZE_BITS);
+	cp = rd_start;
+	while (nblocks) {
+		if (nblocks > 2) 
+			bh = breada(ROOT_DEV, block, block+1, block+2, -1);
+		else
+			bh = bread(ROOT_DEV, block);
+		if (!bh) {
+			printk("I/O error on block %d, aborting load\n", 
+				block);
+			return;
+		}
+		(void) memcpy(cp, bh->b_data, BLOCK_SIZE);
+		brelse(bh);
+		printk("\010\010\010\010\010%4dk",i);
+		cp += BLOCK_SIZE;
+		block++;
+		nblocks--;
+		i++;
+	}
+	printk("\010\010\010\010\010done \n");
+	ROOT_DEV=0x0101;
+}