I have a few queries regarding the buffer headers in linux. 1. As per my understanding, block number in this stucture corresponds to the block no of the data on a logical device rather than on a physical device (hard disk). 2. Why do we need pointer to a pointer for hash list ? As per Maurice Bach book on OS, the hash list and free list both are implemented as a circular, doubly link list. In the below, we have used a pointer for free list, then why pointer to pointer has been used for hash list. struct buffer_head { /* First cache line: */ struct buffer_head *b_next; /* Hash queue list */ struct buffer_head *b_next_free;/* lru/free list linkage */ struct buffer_head *b_prev_free;/* doubly linked list of buffers */ struct buffer_head **b_pprev; /* doubly linked list of hash-queue */ // Rest part of sructure has been stripped off. }; Can anyone clarify my these queries. Thanks & Regard Dinesh ________________________________________________________________________ Yahoo! India Matrimony: Find your life partner online Go to: http://yahoo.shaadi.com/india-matrimony -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/