Hi,
> On 27. Jun 2025, at 08:44, Dominique Martinet <asmadeus@xxxxxxxxxxxxx> wrote:
>
> Hi all,
>
> sorry for the slow reply; I wasn't in Cc of most of the mails back in
> October so this is a pain to navigate... Let me recap a bit:
> - stuff started failing in 6.12-rc1
yes, to my knowledge and interpretation of this thread.
> - David first posted "9p: Don't revert the I/O iterator after
> reading"[1], which fixed the bug, but then found a "better" fix as
> "iov_iter: Fix iov_iter_get_pages*() for folio_queue" [2] which was
> merged instead (so the first patch was not merged)
>
> But it turns out the second patch is not enough (or causes another
> issue?), and the reverting it + applying first one works, is that
> correct?
> What happens if you keep [2] and just apply [1], does that still bug?
I tried that and the test that so far under all the variations reliably
crashed (or not) is not crashing in this case.
> (I've tried reading through the thread now and I don't even see what was
> the "bad" patch in the first place, although I assume it's ee4cdf7ba857
> ("netfs: Speed up buffered reading") -- was that confirmed?)
I was late to the party, to, so I’ll defer to the others.
> David, as you worked on this at the time it'd be great if you could have
> another look, I have no idea what made you try [1] in the first place
> but unless you think 9p is doing something wrong like double-reverting
> on error or something like that I'd like to understand a bit more what
> happens... Although given 6.12 is getting used more now it could make
> sense to just apply [1] first until we understand, and have a proper fix
> come second -- if someone can confirm we don't need to revert [2].
I guess I confirmed this. However, I’m just barely better than a monkey
here so I can’t tell whether this makes sense from the internal logic of
things.
To repeat, for safety: my test case worked with the situation you described and suggested:
[1] applied on top of 6.12.34 and *not* having [2] reverted.
Christian
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