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From:   Roman Gushchin <guro@fb.com>
To:     "Tobin C. Harding" <tobin@kernel.org>
CC:     Andrew Morton <akpm@linux-foundation.org>,
        Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Matthew Wilcox <willy@infradead.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v5 1/7] list: Add function list_rotate_to_front()
Thread-Topic: [PATCH v5 1/7] list: Add function list_rotate_to_front()
Thread-Index: AQHU6ai/hRRVJsHCh0Ws9dfflaiJBKYquiKA
Date:   Wed, 3 Apr 2019 17:57:42 +0000
Message-ID: <20190403175739.GB6778@tower.DHCP.thefacebook.com>
References: <20190402230545.2929-1-tobin@kernel.org>
 <20190402230545.2929-2-tobin@kernel.org>
In-Reply-To: <20190402230545.2929-2-tobin@kernel.org>
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On Wed, Apr 03, 2019 at 10:05:39AM +1100, Tobin C. Harding wrote:
> Currently if we wish to rotate a list until a specific item is at the
> front of the list we can call list_move_tail(head, list).  Note that the
> arguments are the reverse way to the usual use of list_move_tail(list,
> head).  This is a hack, it depends on the developer knowing how the
> list_head operates internally which violates the layer of abstraction
> offered by the list_head.  Also, it is not intuitive so the next
> developer to come along must study list.h in order to fully understand
> what is meant by the call, while this is 'good for' the developer it
> makes reading the code harder.  We should have an function appropriately
> named that does this if there are users for it intree.
>=20
> By grep'ing the tree for list_move_tail() and list_tail() and attempting
> to guess the argument order from the names it seems there is only one
> place currently in the tree that does this - the slob allocatator.
>=20
> Add function list_rotate_to_front() to rotate a list until the specified
> item is at the front of the list.
>=20
> Signed-off-by: Tobin C. Harding <tobin@kernel.org>

Reviewed-by: Roman Gushchin <guro@fb.com>