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SubjectRe: 2.6.19 file content corruption on ext3


On Sun, 17 Dec 2006, Linus Torvalds wrote:
>
> So we should probably do a "wait_for_page()" in do_no_page()?
>
> Or maybe only do it for write accesses (since we don't really care about
> getting mapped readably)? If so, we need to do it in the write case of
> do_no_page() _and_ in the do_wp_page() case. Hmm?

I think we discussed doing exactly this at some earlier time, actually,
just to try to throttle people who do lots of page dirtying.

Maybe we even do it somewhere, but I tried to see it, and in the normal
"nopage()" routine we very much try to _avoid_ locking the page (ie if
it's marked PageUptodate() we'll return it whether locked or not). Which
is fine - especially for readers, there really isn't any reason to ever
delay them getting access to a page just because it's locked for write-out
or something (once it's mapped, they'll have access to it regardless of
any locked state in the kernel anyway).

So I don't actually see any serialization at all that would keep a random
page from being paged back in.

Linus
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