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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 14 Feb 2020 14:07:48 -0800
Message-ID: <CAHk-=wixEw+wKJzwfEFnBYLNt5zU6zA2kpNVu_36e33_zsawKA@mail.gmail.com>
Subject: Re: [GIT PULL] io_uring fixes for 5.6-rc2
To:     Jens Axboe <axboe@kernel.dk>
Cc:     io-uring <io-uring@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Fri, Feb 14, 2020 at 8:45 AM Jens Axboe <axboe@kernel.dk> wrote:
>
> Here's a set of fixes for io_uring that should go into this release.

Whaa?

          for_each_node(node) {
+                if (!node_online(node))
+                        continue;

that's just silly.

We have 'for_each_online_node()' for this.

There's something like four patterns of that pointless thing.

And in io_wq_create(), do you really want to allocate that wqe for
nodes that aren't online? Right now you _allocate_ the node data for
them (using a non-node-specific allocation), but then you won't
actually create the thread for them io_wq_manager().

Plus if the node online status changes, it looks like you'll mess up
_anyway_, in that  io_wq_manager() will first create the workers on
one set of nodes, but then perhaps set the state flags for a
completely different set of nodes if some onlining/offlining has
happened.

I've pulled this, but Jens, you need to be more careful. This all
looks like completely random state that nobody spent any time thinking
about.

Seriously, this "io_uring FIXES ONLY" needs to be stricter than what
you seem to be doing here. This "fix" is opening up a lot of new
possibilities for inconsistencies in the data structures.

               Linus