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

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Date: Mon, 6 May 2024 09:18:28 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Rick Edgecombe <rick.p.edgecombe@...el.com>
Cc: akpm@...ux-foundation.org, Liam.Howlett@...cle.com, bp@...en8.de,
	bpf@...r.kernel.org, broonie@...nel.org,
	christophe.leroy@...roup.eu, dan.j.williams@...el.com,
	dave.hansen@...ux.intel.com, debug@...osinc.com, hpa@...or.com,
	io-uring@...r.kernel.org, keescook@...omium.org,
	kirill.shutemov@...ux.intel.com, linux-cxl@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, linux-s390@...r.kernel.org,
	linux-sgx@...r.kernel.org, luto@...nel.org, mingo@...hat.com,
	nvdimm@...ts.linux.dev, peterz@...radead.org,
	sparclinux@...r.kernel.org, tglx@...utronix.de, x86@...nel.org
Subject: Re: [PATCH] mm: Remove mm argument from mm_get_unmapped_area()

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.

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..