linux-kernel - Re: [PATCH] mm: Remove mm argument from mm_get_unmapped

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Date: Tue, 7 May 2024 13:51:13 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
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 Dan J" <dan.j.williams@...el.com>, "broonie@...nel.org" <broonie@...nel.org>
Subject: Re: [PATCH] mm: Remove mm argument from mm_get_unmapped_area()

On Mon, 2024-05-06 at 09:18 -0700, Christoph Hellwig wrote:
> > On Mon, May 06, 2024 at 09:07:47AM -0700, Rick Edgecombe wrote:
> > > >         if (flags & MAP_FIXED) {
> > > >                 /* Ok, don't mess with it. */
> > > > -               return mm_get_unmapped_area(current->mm, NULL,
> > > > orig_addr, > > len, pgoff, flags);
> > > > +               return current_get_unmapped_area(NULL, orig_addr, len, >
> > > > > pgoff, flags);
> > 
> > The old name seems preferable because it's not as crazy long.  In fact
> > just get_unmapped_area would be even better, but that's already taken
> > by something else.

Ok.

> > 
> > Can we maybe take a step back and sort out the mess of the various
> > _get_unmapped_area helpers?
> > 
> > e.g. mm_get_unmapped_area_vmflags just wraps
> > arch_get_unmapped_area_topdown_vmflags and
> > arch_get_unmapped_area_vmflags, and we might as well merge all three
> > by moving the MMF_TOPDOWN into two actual implementations?
> > 
> > And then just update all the implementations to always pass the
> > vm_flags instead of having separate implementations with our without
> > the flags.
> > 
> > And then make __get_unmapped_area static in mmap.c nad move the
> > get_unmapped_area wrappers there.  And eventually write some
> > documentation for the functions based on the learnings who actually
> > uses what..

The rest of the series[0] is in the mm-tree/linux-next currently. Are you
suggesting we not do this patch, and leave the rest you describe here for the
future? I think the removal of the indirect branch is at least a positive step
forward.


[0]
https://lore.kernel.org/lkml/20240326021656.202649-1-rick.p.edgecombe@intel.com/