Re: [lc-devel] Chunk list issues

[Mauricio L. <mau...@gm...>]

Hi Gupta,

On 6/21/06, Nitin Gupta <nit...@gm...> wrote:
> Hi Mauricio,
>
> Mauricio Lin wrote:
> > Regarding the master chunk list (chunks) in the struct chunk, does it
> > store the chunks of one page cache or several page caches? Will be
> > there one master chunk list per page cache radix tree?
>
> 'master chunk list' is list of all chunks -- these chunks may be part of a file,
> part of anon page, or free chunks. Its there to easily merge physically adjacent
> chunks when a chunk is freed.

You mean there will be one master chunk list for several page cache
radix tree, right?

>
> >
> > I also wonder where the chunk list header will be stored. For instance
> > the list header of task_struct is stored in the tasks field of
> > init_task, so when an insertion happens in the list of task_struct,
> > something like that is used:
> >
> > list_add_tail(&p->tasks, &init_task.tasks);
> >
> > where the first argument is the element to be inserted and the second
> > argument corresponds the list header of task_struct.
> > Thus where the list header of chunks will be stored? Any idea?
> >
>
> A compressed page is stored in many chunks. chunk_head->chunk_list is made to
> point to first of these chunks and these 'related' chunks are linked together
> using chunk->next

OK, I know about the chunk_list purpose, but chunk_list is not the
header of master chunk list, since it is not a list_head. What I am
trying to say is if you want to add something in the master chunk
list, you have to use a function as list_add_tail() (or similar one in
include/linux/list.h) and a header list is needed for representing and
manipulating the master chunk list. If you are going to add something
in the master chunk list, certainly functions in include/linux/list.h
need be used. Let's suppose that list_add_tail() function is used to
insert a chunk in the list, so in this way something like this is
used:

list_add_tail(&chk->chunks, chunk_list_head);

chk is a instance of struct chunk, where the field "chunks" is used to
link to the list.
chunk_list_head is the header of chunk list of type 'list_head'
(because every list has a header)

Such can be declared and initiliazed as:
static LIST_HEAD(chunk_list_head);

The chunk_list_head  (header of master chunk list) must be stored in
some place. So my question is where it is going to be stored ?

BR,

Mauricio Lin.