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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Mon, 4 Mar 2024 10:32:25 -0800
Message-ID: <CAHk-=wgrmt875HJNUY9a-ti0M6M1m6jHEGvCSjcOfXy_E7_X_w@mail.gmail.com>
Subject: Re: [bug report] dead loop in generic_perform_write() //Re: [PATCH v7
 07/12] iov_iter: Convert iterate*() to inline funcs
To: David Howells <dhowells@redhat.com>
Cc: Tong Tiangen <tongtiangen@huawei.com>, Al Viro <viro@kernel.org>, 
	Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>, Christian Brauner <christian@brauner.io>, 
	David Laight <David.Laight@aculab.com>, Matthew Wilcox <willy@infradead.org>, 
	Jeff Layton <jlayton@kernel.org>, linux-fsdevel@vger.kernel.org, 
	linux-block@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, 
	linux-kernel@vger.kernel.org, Kefeng Wang <wangkefeng.wang@huawei.com>
Content-Type: text/plain; charset="UTF-8"

On Mon, 4 Mar 2024 at 03:56, David Howells <dhowells@redhat.com> wrote:
>
> That said, I wonder if:
>
>         #ifdef copy_mc_to_kernel
>
> should be:
>
>         #ifdef CONFIG_ARCH_HAS_COPY_MC

Hmm. Maybe. We do have that

  #ifdef copy_mc_to_kernel

pattern already in <linux/uaccess.h>, so clearly we've done it both ways.

I personally like the "just test for the thing you are using" model,
which is then why I did it that way, but I don't have hugely strong
opinions on it.

> and whether it's possible to find out dynamically if MCEs can occur at all.

I really wanted to do something like that, and look at the source page
to decide "is this a pmem page that can cause machine checks", but I
didn't find any obvious way to do that.

Improvement suggestions more than welcome.

               Linus