Re: [patch 1/3] add the fsblock layer

[Nick Piggin]

Chris Mason wrote:
> On Mon, Jun 25, 2007 at 05:41:58PM +1000, Nick Piggin wrote:
>
> > Neil Brown wrote:

> > > Why do you think you need PG_blocks?
> >
> > Block device pagecache (buffer cache) has to be able to accept
> > attachment of either buffers or blocks for filesystem metadata,
> > and call into either buffer.c or fsblock.c based on that.
> >
> > If the page flag is really important, we can do some awful hack
> > like assuming the first long of the private data is flags, and
> > those flags will tell us whether the structure is a buffer_head
> > or fsblock ;) But for now it is just easier to use a page flag.
>
>
> The block device pagecache isn't special, and certainly isn't that much
> code.  I would suggest keeping it buffer head specific and making a
> second variant that does only fsblocks.  This is mostly to keep the
> semantics of PagePrivate sane, lets not fuzz the line.

That would require a new inode and address_space for the fsblock
type blockdev pagecache, wouldn't it? I just can't think of a
better non-intrusive way of allowing a buffer_head filesystem and
an fsblock filesystem to live on the same blkdev together.

--
SUSE Labs, Novell Inc.
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