diff -urNp 2.5.47/drivers/block/ll_rw_blk.c hangs-2.5/drivers/block/ll_rw_blk.c
--- 2.5.47/drivers/block/ll_rw_blk.c	Tue Nov 12 01:59:41 2002
+++ hangs-2.5/drivers/block/ll_rw_blk.c	Tue Nov 12 02:37:42 2002
@@ -1281,12 +1281,13 @@ static struct request *get_request_wait(
 
 	spin_lock_prefetch(q->queue_lock);
 
-	generic_unplug_device(q);
 	do {
 		prepare_to_wait_exclusive(&rl->wait, &wait,
 					TASK_UNINTERRUPTIBLE);
-		if (!rl->count)
+		if (!rl->count){
+			generic_unplug_device(q);
 			io_schedule();
+		}
 		finish_wait(&rl->wait, &wait);
 		spin_lock_irq(q->queue_lock);
 		rq = get_request(q, rw);
@@ -1487,8 +1488,11 @@ void __blk_put_request(request_queue_t *
 		rl->count++;
 		if (rl->count >= queue_congestion_off_threshold())
 			clear_queue_congested(q, rw);
-		if (rl->count >= batch_requests && waitqueue_active(&rl->wait))
-			wake_up(&rl->wait);
+		if (rl->count >= batch_requests) {
+			smp_mb();
+			if (waitqueue_active(&rl->wait))
+				wake_up(&rl->wait);
+		}
 	}
 }
 
diff -urNp 2.5.47/fs/buffer.c hangs-2.5/fs/buffer.c
--- 2.5.47/fs/buffer.c	Tue Nov 12 01:59:42 2002
+++ hangs-2.5/fs/buffer.c	Tue Nov 12 02:47:46 2002
@@ -135,9 +135,10 @@ void __wait_on_buffer(struct buffer_head
 	get_bh(bh);
 	do {
 		prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
-		blk_run_queues();
-		if (buffer_locked(bh))
+		if (buffer_locked(bh)) {
+			blk_run_queues();
 			schedule();
+		}
 	} while (buffer_locked(bh));
 	put_bh(bh);
 	finish_wait(wqh, &wait);
@@ -1727,7 +1728,8 @@ done:
 		if (uptodate)
 			SetPageUptodate(page);
 		end_page_writeback(page);
-	}
+	} else
+		wakeup_page_waiters(page);
 	if (err == 0)
 		return ret;
 	return err;
@@ -2011,6 +2013,7 @@ int block_read_full_page(struct page *pa
 		else
 			submit_bh(READ, bh);
 	}
+	wakeup_page_waiters(page);
 	return 0;
 }
 
@@ -2315,6 +2318,8 @@ static int end_bio_bh_io_sync(struct bio
 int submit_bh(int rw, struct buffer_head * bh)
 {
 	struct bio *bio;
+	int ret;
+	wait_queue_head_t *wqh = bh_waitq_head(bh);
 
 	BUG_ON(!buffer_locked(bh));
 	BUG_ON(!buffer_mapped(bh));
@@ -2348,7 +2353,13 @@ int submit_bh(int rw, struct buffer_head
 	bio->bi_end_io = end_bio_bh_io_sync;
 	bio->bi_private = bh;
 
-	return submit_bio(rw, bio);
+	ret =  submit_bio(rw, bio);
+
+	smp_mb(); /* spin_unlock may have inclusive semantics */
+	if (waitqueue_active(wqh))
+		wake_up(wqh);
+
+	return ret;
 }
 
 /**
diff -urNp 2.5.47/fs/reiserfs/inode.c hangs-2.5/fs/reiserfs/inode.c
--- 2.5.47/fs/reiserfs/inode.c	Thu Oct 31 01:42:25 2002
+++ hangs-2.5/fs/reiserfs/inode.c	Tue Nov 12 02:50:47 2002
@@ -1987,6 +1987,7 @@ static int reiserfs_write_full_page(stru
     */
     if (nr) {
         submit_bh_for_writepage(arr, nr) ;
+	wakeup_page_waiters(page);
     } else {
         end_page_writeback(page) ;
     }
diff -urNp 2.5.47/include/linux/pagemap.h hangs-2.5/include/linux/pagemap.h
--- 2.5.47/include/linux/pagemap.h	Tue Nov 12 01:59:43 2002
+++ hangs-2.5/include/linux/pagemap.h	Tue Nov 12 02:45:27 2002
@@ -122,4 +122,7 @@ static inline void wait_on_page_writebac
 }
 
 extern void end_page_writeback(struct page *page);
+
+extern void wakeup_page_waiters(struct page * page);
+
 #endif /* _LINUX_PAGEMAP_H */
diff -urNp 2.5.47/mm/filemap.c hangs-2.5/mm/filemap.c
--- 2.5.47/mm/filemap.c	Tue Nov 12 01:59:43 2002
+++ hangs-2.5/mm/filemap.c	Tue Nov 12 02:44:59 2002
@@ -272,9 +272,10 @@ void wait_on_page_bit(struct page *page,
 
 	do {
 		prepare_to_wait(waitqueue, &wait, TASK_UNINTERRUPTIBLE);
-		sync_page(page);
-		if (test_bit(bit_nr, &page->flags))
+		if (test_bit(bit_nr, &page->flags)) {
+			sync_page(page);
 			io_schedule();
+		}
 	} while (test_bit(bit_nr, &page->flags));
 	finish_wait(waitqueue, &wait);
 }
@@ -336,15 +337,30 @@ void __lock_page(struct page *page)
 
 	while (TestSetPageLocked(page)) {
 		prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
-		sync_page(page);
-		if (PageLocked(page))
+		if (PageLocked(page)) {
+			sync_page(page);
 			io_schedule();
+		}
 	}
 	finish_wait(wqh, &wait);
 }
 EXPORT_SYMBOL(__lock_page);
 
 /*
+ * This must be called after every submit_bh with end_io
+ * callbacks that would result into the blkdev layer waking
+ * up the page after a queue unplug.
+ */
+void wakeup_page_waiters(struct page * page)
+{
+	wait_queue_head_t * wqh;
+
+	wqh = page_waitqueue(page);
+	if (waitqueue_active(wqh))
+		wake_up(wqh);
+}
+
+/*
  * a rather lightweight function, finding and getting a reference to a
  * hashed page atomically.
  */
diff -urNp 2.5.47/mm/page_io.c hangs-2.5/mm/page_io.c
--- 2.5.47/mm/page_io.c	Thu Oct 31 01:41:56 2002
+++ hangs-2.5/mm/page_io.c	Tue Nov 12 02:50:12 2002
@@ -104,6 +104,7 @@ int swap_writepage(struct page *page)
 	SetPageWriteback(page);
 	unlock_page(page);
 	submit_bio(WRITE, bio);
+	wakeup_page_waiters(page);
 out:
 	return ret;
 }
@@ -121,6 +122,7 @@ int swap_readpage(struct file *file, str
 	}
 	inc_page_state(pswpin);
 	submit_bio(READ, bio);
+	wakeup_page_waiters(page);
 out:
 	return ret;
 }
--- hangs-2.5/kernel/ksyms.c.~1~	Tue Nov 12 01:59:43 2002
+++ hangs-2.5/kernel/ksyms.c	Tue Nov 12 04:36:37 2002
@@ -336,6 +336,7 @@ EXPORT_SYMBOL(filemap_fdatawrite);
 EXPORT_SYMBOL(filemap_fdatawait);
 EXPORT_SYMBOL(lock_page);
 EXPORT_SYMBOL(unlock_page);
+EXPORT_SYMBOL(wakeup_page_waiters);
 
 /* device registration */
 EXPORT_SYMBOL(register_chrdev);