linux-kernel - Re: [PATCH 2/3] mm: update core kernel code to use vm_flags

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Message-ID: <69860c97-8a76-4ce5-b1d6-9d7c8370d9cd@lucifer.local>
Date: Fri, 1 Aug 2025 12:20:02 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Uladzislau Rezki <urezki@...il.com>
Cc: Harry Yoo <harry.yoo@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
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Subject: Re: [PATCH 2/3] mm: update core kernel code to use vm_flags_t
 consistently

So sorry Ulad, I meant to get back to you on this sooner!

On Tue, Jul 29, 2025 at 08:39:01PM +0200, Uladzislau Rezki wrote:
> On Tue, Jul 29, 2025 at 06:25:39AM +0100, Lorenzo Stoakes wrote:
> > Andrew - FYI there's nothing to worry about here, the type remains
> > precisely the same, and I'll send a patch to fix this trivial issue so when
> > later this type changes vmalloc will be uaffected.
> >
> > On Tue, Jul 29, 2025 at 09:15:51AM +0900, Harry Yoo wrote:
> > > [Adding Uladzislau to Cc]
> >
> > Ulad - could we PLEASE get rid of 'vm_flags' in vmalloc? It's the precise
> > same name and (currently) type as vma->vm_flags and is already the source
> > of confusion.
> >
> You mean all "vm_flags" variable names? "vm_struct" has flags as a
> member. So you want:
>
> urezki@...38:~/data/backup/coding/linux-not-broken.git$ grep -rn vm_flags mm/execmem.c
> 29:                          pgprot_t pgprot, unsigned long vm_flags)
> 39:             vm_flags |= VM_DEFER_KMEMLEAK;
> 41:     if (vm_flags & VM_ALLOW_HUGE_VMAP)
> 45:                              pgprot, vm_flags, NUMA_NO_NODE,
> 51:                                      pgprot, vm_flags, NUMA_NO_NODE,
> 85:                          pgprot_t pgprot, unsigned long vm_flags)
> 259:    unsigned long vm_flags = VM_ALLOW_HUGE_VMAP;
> 266:    p = execmem_vmalloc(range, alloc_size, PAGE_KERNEL, vm_flags);
> 376:    unsigned long vm_flags = VM_FLUSH_RESET_PERMS;
> 385:            p = execmem_vmalloc(range, size, pgprot, vm_flags);
> urezki@...38:~/data/backup/coding/linux-not-broken.git$ grep -rn vm_flags mm/vmalloc.c
> 3853: * @vm_flags:                additional vm area flags (e.g. %VM_NO_GUARD)
> 3875:                   pgprot_t prot, unsigned long vm_flags, int node,
> 3894:   if (vmap_allow_huge && (vm_flags & VM_ALLOW_HUGE_VMAP)) {
> 3912:                             VM_UNINITIALIZED | vm_flags, start, end, node,
> 3977:   if (!(vm_flags & VM_DEFER_KMEMLEAK))
> 4621:   vm_flags_set(vma, VM_DONTEXPAND | VM_DONTDUMP);
> urezki@...38:~/data/backup/coding/linux-not-broken.git$ grep -rn vm_flags mm/execmem.c
> 29:                          pgprot_t pgprot, unsigned long vm_flags)
> 39:             vm_flags |= VM_DEFER_KMEMLEAK;
> 41:     if (vm_flags & VM_ALLOW_HUGE_VMAP)
> 45:                              pgprot, vm_flags, NUMA_NO_NODE,
> 51:                                      pgprot, vm_flags, NUMA_NO_NODE,
> 85:                          pgprot_t pgprot, unsigned long vm_flags)
> 259:    unsigned long vm_flags = VM_ALLOW_HUGE_VMAP;
> 266:    p = execmem_vmalloc(range, alloc_size, PAGE_KERNEL, vm_flags);
> 376:    unsigned long vm_flags = VM_FLUSH_RESET_PERMS;
> 385:            p = execmem_vmalloc(range, size, pgprot, vm_flags);
> urezki@...38:~/data/backup/coding/linux-not-broken.git$ grep -rn vm_flags ./include/linux/vmalloc.h
> 172:                    pgprot_t prot, unsigned long vm_flags, int node,
> urezki@...38:~/data/backup/coding/linux-not-broken.git$
>
> to rename all those "vm_flags" to something, for example, like "flags"?

Yeah, sorry I know it's a churny pain, but I think it's such a silly source
of confusion _in general_, not only this series where I made a mistake (of
course entirely my fault but certainly more understandable given the
naming), but in the past I've certainly sat there thinking 'hmmm wait' :)

Really I think we should rename 'vm_struct' too, but if that causes _too
much_ churn fair enough.

I think even though it's long-winded, 'vmalloc_flags' would be good, both
in fields and local params as it makes things very very clear.

Equally 'vm_struct' -> 'vmalloc_struct' would be a good change.

Let me know what you think,

>
> Thanks!
>
> --
> Uladzislau Rezki

cheers, Lorenzo