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Howlett" , David Hildenbrand , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Mike Rapoport , Muchun Song , Nikita Kalyazin , Vlastimil Babka , Axel Rasmussen , Andrew Morton , James Houghton , Lorenzo Stoakes , Hugh Dickins , Michal Hocko , Ujwal Kundur , Oscar Salvador , Suren Baghdasaryan , Andrea Arcangeli Subject: Re: [PATCH v4 0/4] mm/userfaultfd: modulize memory types Message-ID: References: <20251014231501.2301398-1-peterx@redhat.com> <78424672-065c-47fc-ba76-c5a866dcdc98@redhat.com> <6odeeo7bgxgq4v6y3jercrriqyreynuelofrw6k6roh7ws5vy2@wyvx7uiztb5y> MIME-Version: 1.0 In-Reply-To: <6odeeo7bgxgq4v6y3jercrriqyreynuelofrw6k6roh7ws5vy2@wyvx7uiztb5y> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: EjbwrAuY7yyuDIH6Uz4oYS8NxwPh3ggux7uT1EnqI3M_1761859575 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Queue-Id: 44472140007 X-Rspamd-Server: rspam11 X-Rspam-User: X-Stat-Signature: 3nt8topf7wf8jaj8a87nutc7ae8p8wsb X-HE-Tag: 1761859588-359254 X-HE-Meta: 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 65tuxslm 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Let me reply in short. On Thu, Oct 30, 2025 at 04:24:46PM -0400, Liam R. Howlett wrote: > Right, so the existing code a huge mess today and you won't fix > anything, ever. IMHO fix is the wrong word. Cleanup it is. I agree the current userfaultfd code isn't extremely easy to follow. > > We currently have a uffd_flags_t that sets wp or not then passes it > through to set another part of the flag to pass it through again. This > is stupid. I feel like you're applying very strongly personal preference to this piece of code. I won't say that is stupid. Axel introduced it, and I think it's still an improvement comparing to before. > > And then it gets more stupid. We then check that flag exactly once for > the second argument in a global function and NEVER LOOK AT THAT PART > AGAIN. So we now have a type to contain a boolean, but we keep passing > through the uffd_flags_t, so we can see if wp is set or not. > > And you're fine with it. In fact, let's add another one. I mean, we > tried for two but people didn't like two so lets whine and whine and > whine until people get frustrated and let you push a second one of those > gems into the code you REFUSED TO MAINTAIN. What I refuse to maintain? I don't really follow. > > This is what owning a problem looks like: I removed the uufd_flags_t, > because it's stupid. I removed all the hugetlb checks because I > modularized the memory types. > > I'm happy to address changes, but I'm not happy to accept more > middleware and "it's not part of the patch set" to address any problem > as you push more trash into an already horrible code base. > > We need to fix things too. > > So I'm fixing it. Let's wait for a 2nd opinion on the approaches. As I said, I'm OK if everyone likes your solution and if I'm the only one NACKing it. If we can support guest-memfd finally whoever adds that, it's not so bad. -- Peter Xu