Re: 2.4.0-test10-pre3:Oops in mm/filemap.c:filemap_write_pa

From: Linus Torvalds (torvalds@transmeta.com)
Date: Mon Oct 23 2000 - 15:49:42 EST


On Mon, 23 Oct 2000, Alexander Viro wrote:

> On Mon, 23 Oct 2000, Linus Torvalds wrote:
>
> > Al, any ideas? I have this feeling that the simplest fix is just to leave
> > the race open, and make truncate_complete_page() just leave such a "racy"
> > page in the page cache. It will still race, and the invalid page will
> > still exist, but the end result should be harmless.
>
> Provided that we clean it - why the hell do we want to take it out of
> the pagecache? I don't see any fundamental reasons to prohibit pages
> past the ->i_size being hashed.

In fact, we used to allow them.

We do want to remove it from the page cache under normal circumstances: it
makes for much better MM behaviour (ie free pages that are truly useless).
But I suspect that just adding a test for "page_count(page) == 1" (ie same
as for the page cache invalidation) before freeing it should give that
advantage, along with avoiding the problematic unlikely case...

                Linus

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