Hi,
On Mon, 01 Nov 1999 15:58:33 -0600, [EMAIL PROTECTED] said:
> I agree with this, it feels closer to the linux page cache, the
> terminology in the XFS white paper is a little confusing here.
> XFS on Irix caches file data in buffers, but not in the regular buffer
> cache, they are cached off the vnode and organized by logical file
> offset rather than by disk block number,
This is describing the job done by the page cache, not the buffer cache,
in Linux.
> the memory in these buffers comes from the page subsystem, the page
> tag being the vnode and file offset. These buffers do not have to have
> a physical disk block associated with them, XFS allows you to reserve
> blocks on the disk for a file without picking which blocks. At some
> point when the data needs to be written (memory pressure, or sync
> activity etc)
The main thing we'd want to establish to support this fully in Linux is
exactly this --- what VM callbacks do you need here? Memory pressure is
not currently something that gets fed back adequately to the
filesystems, and I'll be needing similar feedback for ext2 journaling
(we need to be told to do early commits if the memory used by a
transaction is required elsewhere).
The details of the IOs themselves should be capable of being handled
perfectly well within the existing device driver abstraction: you don't
need to use the buffer cache.
--Stephen
