bcache.c

		block->blocknum = blocknum;
		err = bio_read(cache->dev, block->ptr, (off_t)blocknum * cache->block_size, cache->block_size );

		if(block->ptr == (void *)0x8f76c0e4) {
		    char * p = ((char *)block->ptr);
		    thread_sleep(1);
		    while((p < (char *) 0x8f76d0e4) && (*p != 0x99))
			p++;
		    p-=4;
		    dprintf(SPEW, "%x: %x %x %x %x  %x %x %x %x %d %d\n",
			    p, 
			    p[0], p[1], p[2], p[3],
			    p[4], p[5], p[6], p[7],
			    cache->block_size, err);
			    
		}
		if (err < 0) {
			/* free the block, return an error */
			list_add_tail(&cache->free_list, &block->node);
			return NULL;
		}
		if (err < 4096) {
		  dprintf(SPEW, "short read %d at %d\n", err, blocknum);
		}

[1190] 8f76d0bc: 0 0 0 0 99 99 99 99 4096 4096