Hi, I've a question regarding how to check if a buffer head is valid. Suppose that I've read in a block using sb_bread and that buffer head hasn't been touched in a while so that it's uptodate. Now suppose that somebody drops the caches from user space. I looked at the code and found the following, Beginning from drop_caches_sysctl_handler --->iterate_supers ---->drop_pagecache_sb --->invalidate_mapping_pages ---->invalidate_inode_page --->invalidate_complete_page --->try_to_release_page In the try_to_release_page there's call to try_to_free_buffers Now since i would be having a pointer to the buffer head which is already uptodate and nothing going on with it this would actually free the buffer. There's a call to kmem_cache_free, so i would be left with a pointer which is invalid [Correct?] Now how do I check if i need to re-read this buffer from disk since the pointer is actually not valid anymore so checking for bh_uptodate doesn't make sense. Reading the buffer from disk always isn't something i'm looking for so any advice on how to check it? Regards, Pranay Kr. Srivastava -- Pranay Srivastava