While going through Page Cache explanation in "Professional Linux Kernel" book I came across one term called "address space" ( not related to virtual or physical address space ) I did not get what is the meaning of this address space, following is verbatim description: "To manage the various target objects that can be processed and cached in whole pages, the kernel uses an abstraction of the "address space" that associates the pages in memory with a specific block device (or any other system unit or part of a system unit). This type of address space must not be confused with the virtual and physical address spaces provided by the system or processor. It is a separate abstraction of the Linux kernel that unfortunately bears the same name. Initially, we are interested in only one aspect. Each address space has a "host" from which it obtains its data. In most cases, these are inodes that represent just one file.[2] Because all existing inodes are linked with their superblock (as discussed in Chapter 8), all the kernel need do is scan a list of all superblocks and follow their associated inodes to obtain a list of cached pages" Can anyone please explain what is the use of this and what this is all about? Regards, Piyush