why sum(bdev->bd_inode->i_mapping->nrpages) is not nr_pagecache?
I am new to Linux Mem management, and learning...
Normally when a new page is added to radix tree, address_space nrpages is incremented by 1 as well as the global variable nr_pagecache. Same when a page is removed from the tree.
Then I do not understand why then sum(nr_pages) is much smaller (10 to 20MB) than nr_pagecache (can be x00MB)... I got those numbers from statistics reported in /proc/meminfo,
Can you hint me how to find answer?