Re: Buffer state bits

[Jamie Lokier <jamie@shareable.org>]

Jan Kara wrote:
> BH_Dirty
> - Ideally, this bit should mean "buffer has data that have to be
>   written". But it is not quite true. The problem happens when
>   someone calls set_page_dirty() on the page to which buffers are
>   attached or similarly when buffers are attached to a dirty
>   page. Then all buffers attached to the page are marked dirty -
>   even those that are beyond end of file which obviously should not
>   be written.
> 
>   When buffer is dirty, the page has to be dirty as well (mark
>   buffer dirty takes care of that). It is not necessarily the other
>   way around and buffer dirty bit is what ultimately decides whether
>   the buffer goes to disk or not.

That last sentence implies page can be dirty while a buffer in the
page is not dirty.

In that case, do buffers beyond the end of file need to be set dirty
by set_page_dirty()?  If yes, perhaps the text could explain why.

-- Jamie