Re: Addressing logically the buffer cache

[Juan <piernas@ditec.um.es>]

Alexander Viro escribió:
> 
> On Tue, 14 Nov 2000, Juan wrote:
> 
> > Hi!.
> >
> > Is there any patch or project to address logically the buffer cache?.
> > Now, you use three parameters to find a buffer in cache: device, block
> > number, and block size. But, what about if I want to find a buffer using
> > a super block, an inode number, and a block number within the file
> > specified by the inode number.
> 
> What's wrong with using the pagecache and per-page buffer_heads?

Suppose you are implementing a log-structured file system and a process
adds a new logical block to a file. Besides, suppose that the segment is
512 KBytes in size. Usually, you don't want to write the segment before
it is full. The logical block hasn't got a physical address because you
don't build the segment until it is written to disk. So, what happens if
another process wants to access to the new block?.

You can't assign a physical address to the new block because the address
can change when the buffer is written to disk.

Perhaps, I'm wrong, but I think that the implementation of the BSD-LFS
needs to address logically the buffer cache.

Bye!

P.D.: sorry for my bad English ;-)
-- 
D. Juan Piernas Cánovas
Departamento de Ingeniería y Tecnología de Computadores
Facultad de Informática. Universidad de Murcia
Campus de Espinardo - 30080 Murcia (SPAIN)
Tel.: +34968364633    Fax: +34968364151
email: piernas@ditec.um.es
PGP public key:
http://pgp.rediris.es:11371/pks/lookup?search=piernas%40ditec.um.es&op=index
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