Re: Design problems caused by bdflush

[Jamie Lokier]

Daniel Phillips wrote:
> In the end I think that the buffer system ought to be virtualized in
> the same way as the rest of vfs, with some as-yet unidentified set of
> operations that can be taken as defaults or overridden as required.
> This would allow the buffer behaviour to be tuned on a
> per-filesystem/partition basis, which would be right and proper.

A possibly simple change would be another buffer state: "dependent
dirty".  Unlike dirty buffers they are not flushed and they're not on
the dirty list; instead, they are linked to from an ordinary dirty
buffer.

After an ordinary dirty buffer is written or flushed, its "dependent
dirty" buffers are changed to "dirty" and they will eventually be
written too.  Thus you get a partial write ordering.

The API is mark_buffer_dependent_dirty(buffer, parent), nothing more.

-- Jamie