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

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Date: Tue, 7 May 2024 12:06:05 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
Cc: "x86@...nel.org" <x86@...nel.org>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        "luto@...nel.org" <luto@...nel.org>,
        "linux-cxl@...r.kernel.org" <linux-cxl@...r.kernel.org>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "debug@...osinc.com" <debug@...osinc.com>,
        "io-uring@...r.kernel.org" <io-uring@...r.kernel.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "christophe.leroy@...roup.eu" <christophe.leroy@...roup.eu>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>,
        "hpa@...or.com" <hpa@...or.com>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "nvdimm@...ts.linux.dev" <nvdimm@...ts.linux.dev>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "bp@...en8.de" <bp@...en8.de>,
        "Williams, 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()

* Edgecombe, Rick P <rick.p.edgecombe@...el.com> [240507 09:51]:
> On Mon, 2024-05-06 at 12:32 -0400, Liam R. Howlett wrote:
> > 
> > I like this patch.
> 
> Thanks for taking a look.
> 
> > 
> > I think the context of current->mm is implied. IOW, could we call it
> > get_unmapped_area() instead?  There are other functions today that use
> > current->mm that don't start with current_<whatever>.  I probably should
> > have responded to Dan's suggestion with my comment.
> 
> Yes, get_unmapped_area() is already taken. What else to call it... It is kind of
> the process "default" get_unmapped_area(). But with Christoph's proposal it
> would basically be arch_get_unmapped_area().

unmapped_area(), but that's also taken..

arch_get_unmapped_area() are all quite close.  If you look into it, many
of the arch versions were taken from the sparc 32 version.  Subsequent
changes were made and they are no longer exactly the same, but I believe
functionally equivalent - rather tricky to test though.

I wanted to unite these to simplify the mm code a while back, but have
not gotten back to it.  One aspect that some archs have is "cache
coloring" which does affect the VMAs.

The other difference is VDSO, which I may be looking into soon.  Someone
once called me a glutton for punishment and there may be some truth in
that...

Cheers,
Liam