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Date: Thu, 13 Jun 2024 10:10:16 +0200
From: Christoph Hellwig <hch@lst.de>
To: Nilay Shroff <nilay@linux.ibm.com>
Cc: Keith Busch <kbusch@meta.com>, linux-nvme@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
	hch@lst.de, sagi@grimberg.me, paulmck@kernel.org,
	davidgow@google.com, akpm@linux-foundation.org,
	venkat88@linux.vnet.ibm.com, Keith Busch <kbusch@kernel.org>
Subject: Re: [PATCH 1/2] list: introduce a new cutting helper
Message-ID: <20240613081016.GA21500@lst.de>
References: <20240612155135.3060667-1-kbusch@meta.com> <f0e4c51c-8227-4f5c-876f-38fbb4a0e1bf@linux.ibm.com>
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On Thu, Jun 13, 2024 at 10:26:11AM +0530, Nilay Shroff wrote:
> I am wondering whether we really need the _rcu version of list_cut here?
> I think that @head could point to an _rcu protected list and that's true 
> for this patch. So there might be concurrent readers accessing @head using
> _rcu list-traversal primitives, such as list_for_each_entry_rcu().

Yes, I can't see how this works for a RCU lists without very careful
memory ordering.

Btw, another thing - the old vs new list ordering is reversed vs
list_splice*, which is a bit confusing (as are the parameter names
both for list_splice* and this new helper).  Can you switch them
around to match?