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SubjectRe: [PATCH] fs: nobh_truncate_page() fix


On Mon, 5 Mar 2007, Dave Kleikamp wrote:
>
> This fixes a regression caused by 22c8ca78f20724676b6006232bf06cc3e9299539.
>
> nobh_prepare_write() no longer marks the page uptodate, so
> nobh_truncate_page() needs to do it.

I'm not convinced...

If the page wasn't up-to-date from before, it's *not* necessarily
up-to-date after the truncate either! So why do we have that at all?

The same comment is true of "nobh_commit_write()" (which _does_ have the
SetPageUptodate() there).

So I have three questions:

- why is that valid in the first place (the page is *not* guaranteed to
be up-to-date as far as I can see!)

- why is it valid to do in "nobh_commit_write()"

- why doesn't "nobh_truncate_page()"
(a) call nobh_prepare_write() through an indirect pointer?
(b) call nobh_commit_write() at all? (Yeah, I realize it's because
of brokenness with i_size, so this is more of a "those
functions should be factored out properly" statement rather
than a question.

IOW, I'm sure your patch _fixes_ something, but no, it's certainly not
obvious to me. A few added comments would be good.. Why is it ok to do
this on a page that wasn't up-to-date before (since obviously, if it *was*
up-to-date, it's pointless).

Linus
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