On Thu, Feb 03, 2022 at 02:38:42AM +0000, Liam Howlett wrote: > * Mike Rapoport <rppt@xxxxxxxxxx> [220202 12:11]: > > Hi Liam, > > > > On Wed, Feb 02, 2022 at 02:41:56AM +0000, Liam Howlett wrote: > > > From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx> > > > > > > +The Maple Tree maintains a small memory footprint and was designed to use > > > +modern processor cache efficiently. The most important user of the Maple Tree > > > +is the virtual memory area. > > > > For me it sounds like VMA *is* the maple tree user. Maybe > > > > The most important usage of the Maple Tree is tracking of the virtual > > memory areas. > > > > Thanks, I can see that now. I'm not a fan of either of the ways this is > written but yours is more clear. Maybe you can come up with even better one :) > > > diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h > > > new file mode 100644 > > > index 000000000000..14ddeaa8f3e7 > > > --- /dev/null > > > +++ b/include/linux/maple_tree.h > > > @@ -0,0 +1,673 @@ > > > +/* SPDX-License-Identifier: GPL-2.0+ */ > > > +#ifndef _LINUX_MAPLE_TREE_H > > > +#define _LINUX_MAPLE_TREE_H > > > +/* > > > + * Maple Tree - An RCU-safe adaptive tree for storing ranges > > > + * Copyright (c) 2018 Oracle > > > > 2018 - 2022? > > Wait, what happened in 2019-2022? Did I miss anything? I'm really not a copyright expert, but from what I see the dates in copyright notice use the year when the patches are posted or a range that end in that year. > > > > > + * Authors: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> > > > + * Matthew Wilcox <willy@xxxxxxxxxxxxx> > > > + */ > > > + > > > +#include <linux/kernel.h> > > > +#include <linux/rcupdate.h> > > > +#include <linux/spinlock.h> > > > +/* #define CONFIG_MAPLE_RCU_DISABLED */ > > > +/* #define CONFIG_DEBUG_MAPLE_TREE_VERBOSE */ > > > + > > > +/* > > > + * Allocated nodes are mutable until they have been inserted into the tree, > > > + * at which time they cannot change their type until they have been removed > > > + * from the tree and an RCU grace period has passed. > > > + * > > > + * Removed nodes have their ->parent set to point to themselves. RCU readers > > > + * check ->parent before relying on the value that they loaded from the > > > + * slots array. This lets us reuse the slots array for the RCU head. > > > + * > > > + * Nodes in the tree point to their parent unless bit 0 is set. > > > > There are a lots of comments describing the maple tree internals here and > > below. Did yaou consider adding a section "Implementation details" or > > something like that to the maple_tree.rst and linking these comments there > > with DOC: and some glue text? > > I did. I actually had it in there but moved it into the code in an > effort to avoid the documentation from being a developer doc. I'd like > it to be a user document. I also did not want the implementation > details to be too far away from the code to avoid it being missed when > the code changes. There could be two documents: one for the users and another one with implementation details ;-) The implementation description can then include DOC: parts to keep that documentation close to the code. But if you prefer to skip this part (like most of us do) I'll understand :) > > > +/* > > > + * More complicated stores can cause two nodes to become one or tree and > > > > ^ three? > > Yes, perhaps I typed my accent here :) Or because it's all about trees :) -- Sincerely yours, Mike.
