One vital use of address_space object is by filesystem to manage
page-cache of a file:
- cache recently accessed data in page-cache
- Read-ahead (prefectiching) of data sequentially read data in page-cache
- support memory mapped I/O through page-cache.

Look at address_space_operations vector how it achieve it through
readpage, readpages, writepage and writepages methods to populate and
flush page-cache of an inode.

Thanks,
Rajat

On Mon, Feb 14, 2011 at 4:29 PM, piyush moghe [off-list ref] wrote:

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



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