On Wed, 2006-12-20 at 14:25 -0800, Linus Torvalds wrote:
>
> On Wed, 20 Dec 2006, Dave Kleikamp wrote:
> >
> > This patch removes some questionable code that attempted to make a
> > no-longer-used page easier to reclaim.
>
> If so, "cancel_dirty_page()" may actually be the right thing to use, but
> only if you can guarantee that the page isn't mapped anywhere (and from
> the name of the function I guess it's not something that you'll ever map?)
That's correct. It can't be mapped. It's a private mapping only used
for metadata.
I'm really not sure the code in question is having the intended effect.
Maybe one of the gurus on cc: can take a look at the code and tell me if
it's worth keeping. I apologize in advance if it makes anyone lose
their lunch.
> So the JFS code _looks_ like you could just replace the
>
> clear_page_dirty(page);
>
> with
>
> cancel_dirty_page(page, PAGE_CACHE_SIZE);
>
> (where that second parameter is just used for statistics - it updates the
> "cancelled IO" byte-counts if CONFIG_TASK_IO_ACCOUNTING is set - so the
> number doesn't really matter, you could make it zero if you never want the
> thing to show up in the IO accounting).
I'm not sure whether zero or PAGE_CACHE_SIZE would be better. The
situation is where some page of metadata is no longer used, say
shrinking a directory tree or truncating a file and throwing out the
extent tree.
Thanks,
Shaggy
--
David Kleikamp
IBM Linux Technology Center
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