linux-kernel - Re: [PATCH 0/3] mm/arch: Fix a few collide definition on private use of VM_FAULT

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Date:   Sun, 5 Feb 2023 22:18:30 -0500
From:   Peter Xu <peterx@...hat.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-arm-kernel@...ts.infradead.org, linux-s390@...r.kernel.org
Subject: Re: [PATCH 0/3] mm/arch: Fix a few collide definition on private use
 of VM_FAULT_*

On Mon, Feb 06, 2023 at 02:51:18AM +0000, Matthew Wilcox wrote:
> That wasn't what I meant.  I meant putting VM_FAULT_BADMAP and
> VM_FAULT_SIGSEGV in mm_types.h.  Not having "Here is a range of reserved
> arch private ones".

VM_FAULT_SIGSEGV is there already; I assume you meant adding them all
directly into vm_fault_reason.

Then I don't think it's a good idea..

Currently vm_fault_reason is a clear interface for handle_mm_fault() for
not only arch pffault handlers but also soft faults like GUP.

If handle_mm_fault() doesn't return VM_FAULT_BADMAP at all, I don't think
we should have it as public API at all.  When arch1 people reading the
VM_FAULT_ documents, it shouldn't care about some fault reason that only
happens with arch2.  Gup shouldn't care about it either.

Logically a new page fault handler should handle all the retval of
vm_fault_reason afaiu.  That shouldn't include e.g. VM_FAULT_BADMAP either.

Thanks,

-- 
Peter Xu