diff -urN 2.3.21/fs/buffer.c 2.3.21-ramdisk/fs/buffer.c
--- 2.3.21/fs/buffer.c	Tue Oct 12 18:13:37 1999
+++ 2.3.21-ramdisk/fs/buffer.c	Wed Oct 13 19:50:23 1999
@@ -1207,7 +1207,8 @@
 
 static void unmap_buffer(struct buffer_head * bh)
 {
-	if (buffer_mapped(bh))
+	if (buffer_mapped(bh) &&
+	    MAJOR(bh->b_dev) != RAMDISK_MAJOR)
 	{
 		mark_buffer_clean(bh);
 		wait_on_buffer(bh);
@@ -1217,6 +1218,59 @@
 	}
 }
 
+static void hash_ramdisk_buffers(struct page * page)
+{
+	struct buffer_head * bh = page->buffers, * first = bh, ** head;
+
+	do {
+		if (MAJOR(bh->b_dev) != RAMDISK_MAJOR)
+			BUG();
+		if (buffer_mapped(bh) && buffer_uptodate(bh))
+		{
+			struct buffer_head * oldbh;
+
+			/* the buffer hash doesn't like duplicates */
+			oldbh = get_hash_table(bh->b_dev, bh->b_blocknr,
+					       bh->b_size);
+			if (oldbh)
+			{
+				mark_buffer_clean(oldbh);
+				wait_on_buffer(oldbh);
+				clear_bit(BH_Protected, &oldbh->b_state);
+
+				/* an anonymous buffer is not update */
+				clear_bit(BH_Uptodate, &oldbh->b_state);
+
+				/* make sure the old buffer will be anonymous,
+				   bforget may fail to forget the buffer
+				   if there's some other user */
+				write_lock(&hash_table_lock);
+				if (oldbh->b_pprev)
+					__hash_unlink(oldbh);
+				write_unlock(&hash_table_lock);
+
+				bforget(oldbh);
+			}
+
+			/* stop the I/O before changing the end-io
+			   completation callback */
+			if (buffer_dirty(bh) || buffer_locked(bh))
+			{
+				mark_buffer_clean(bh);
+				wait_on_buffer(bh);
+			}
+			/* need a mb() here?? It seems no. */
+			bh->b_end_io = end_buffer_io_sync;
+
+			head = &hash(bh->b_dev, bh->b_blocknr);
+			write_lock(&hash_table_lock);
+			__hash_link(bh, head);
+			write_unlock(&hash_table_lock);
+		}
+		bh = bh->b_this_page;
+	} while (bh != first);
+}
+
 /*
  * We don't have to release all buffers here, but
  * we have to be sure that no dirty buffer is left
@@ -1262,6 +1316,8 @@
 	if (!offset) {
 		if (!try_to_free_buffers(page)) {
 			atomic_add(PAGE_CACHE_SIZE, &buffermem);
+			if (MAJOR(inode->i_dev) == RAMDISK_MAJOR)
+				hash_ramdisk_buffers(page);
 			return 0;
 		}
 	}
@@ -1445,11 +1501,37 @@
 			if (buffer_new(bh)) {
 				memset(bh->b_data, 0, bh->b_size);
 			} else {
-				ll_rw_block(READ, 1, &bh);
-				wait_on_buffer(bh);
-				err = -EIO;
-				if (!buffer_uptodate(bh))
-					goto out;
+				if (MAJOR(bh->b_dev) != RAMDISK_MAJOR)
+				{
+				do_IO:
+					ll_rw_block(READ, 1, &bh);
+					wait_on_buffer(bh);
+					err = -EIO;
+					if (!buffer_uptodate(bh))
+						goto out;
+				} else {
+					struct buffer_head * oldbh;
+
+					oldbh = get_hash_table(bh->b_dev,
+							       bh->b_blocknr,
+							       bh->b_size);
+					if (!oldbh)
+						goto do_IO;
+					mark_buffer_clean(oldbh);
+					wait_on_buffer(oldbh);
+					clear_bit(BH_Protected,
+						  &oldbh->b_state);
+					if (!buffer_uptodate(oldbh))
+					{
+						bforget(oldbh);
+						goto do_IO;
+					}
+
+					memcpy(bh->b_data, oldbh->b_data,
+					       bh->b_size);
+					set_bit(BH_Protected, &bh->b_state);
+					bforget(oldbh);
+				}
 			}
 		}
 
@@ -1608,11 +1690,37 @@
 			if (buffer_new(bh)) {
 				memset(bh->b_data, 0, bh->b_size);
 			} else {
-				ll_rw_block(READ, 1, &bh);
-				wait_on_buffer(bh);
-				err = -EIO;
-				if (!buffer_uptodate(bh))
-					goto out;
+				if (MAJOR(bh->b_dev) != RAMDISK_MAJOR)
+				{
+				do_IO:
+					ll_rw_block(READ, 1, &bh);
+					wait_on_buffer(bh);
+					err = -EIO;
+					if (!buffer_uptodate(bh))
+						goto out;
+				} else {
+					struct buffer_head * oldbh;
+
+					oldbh = get_hash_table(bh->b_dev,
+							       bh->b_blocknr,
+							       bh->b_size);
+					if (!oldbh)
+						goto do_IO;
+					mark_buffer_clean(oldbh);
+					wait_on_buffer(oldbh);
+					clear_bit(BH_Protected,
+						  &oldbh->b_state);
+					if (!buffer_uptodate(oldbh))
+					{
+						bforget(oldbh);
+						goto do_IO;
+					}
+
+					memcpy(bh->b_data, oldbh->b_data,
+					       bh->b_size);
+					set_bit(BH_Protected, &bh->b_state);
+					bforget(oldbh);
+				}
 			}
 		}
 
@@ -2032,8 +2140,33 @@
 				set_bit(BH_Uptodate, &bh->b_state);
 				continue;
 			}
+			else if (MAJOR(bh->b_dev) == RAMDISK_MAJOR)
+			{
+				struct buffer_head * oldbh;
+
+				oldbh = get_hash_table(bh->b_dev,
+						       bh->b_blocknr,
+						       bh->b_size);
+				if (!oldbh)
+					goto do_IO;
+				mark_buffer_clean(oldbh);
+				wait_on_buffer(oldbh);
+				clear_bit(BH_Protected, &oldbh->b_state);
+				if (!buffer_uptodate(oldbh))
+				{
+					bforget(oldbh);
+					goto do_IO;
+				}
+
+				memcpy(bh->b_data, oldbh->b_data, bh->b_size);
+				set_bit(BH_Uptodate, &bh->b_state);
+				set_bit(BH_Protected, &bh->b_state);
+				bforget(oldbh);
+				continue;
+			}				
 		}
 
+	do_IO:
 		init_buffer(bh, end_buffer_io_async, NULL);
 		atomic_inc(&bh->b_count);
 		arr[nr] = bh;