Re: [RFC] changes to buffer.c (was Test12 ll_rw_block error)

Chris Mason
2000-12-22T14:28:10Z

On Thursday, December 21, 2000 22:38:04 -0200 Marcelo Tosatti <marcelo@conectiva.com.br> wrote:

>
> On Thu, 21 Dec 2000, Andreas Dilger wrote:
>
>> Marcelo Tosatti writes:
>> > It seems your code has a problem with bh flush time.
>> >
>> > In flush_dirty_buffers(), a buffer may (if being called from kupdate) only
>> > be written in case its old enough. (bh->b_flushtime)
>> >
>> > If the flush happens for an anonymous buffer, you'll end up writing all
>> > buffers which are sitting on the same page (with block_write_anon_page),
>> > but these other buffers are not necessarily old enough to be flushed.
>>
>> This isn't really a "problem" however. The page is the _maximum_ age of
>> the buffer before it needs to be written. If we can efficiently write it
>> out with another buffer
>
>
>> (essentially for free if they are on the same spot on disk)
>
> Are you sure this is true for buffer pages in most cases?
>
>

It's a good point. block_write_anon_page could be changed to just write the oldest buffer and redirty the page (if the buffers are far apart). If memory is tight, and we *really* need the page back, it will be flushed by try_to_free_buffers.

It seems a bit nasty to me though...writepage should write the page.

-chris