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linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, fuse-devel@lists.linux.dev, Ihor Solodrai , Bert Karwatzki Subject: Re: [PATCH v5 24/38] mm/vma: enforce that mm-managed mappings may not set VMA_IO_BIT Message-ID: References: <20261009-b4-mmap-prepare-vma-flag-sanify-v5-0-923b70125b1e@kernel.org> <20261009-b4-mmap-prepare-vma-flag-sanify-v5-24-923b70125b1e@kernel.org> <5d51b6b3-ad58-4827-bedf-f1a79ebd5c86@kernel.org> <5ba7305f-0ad1-44ee-be0b-36752684cdb9@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 17B8BC0005 X-Rspam-User: X-Stat-Signature: 6anx4izkzidtrbyxdmd1r1tzutxa3ao5 X-HE-Tag: 1791831502-561556 X-HE-Meta: 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0Jx/1fIQWAgrogEJmyhgIB/M8EQe54R2BXVKurDPdbjGKbRpIAaPTsmNYpwX7v2PNnFcLXo8KyOiPW4DmGk+N6Gcr3LpcJ0WGCfJ5dmhkzBDmc2v9qNoqW6kk2TUtGBD7Bg0ewo9FrCdBwqgjry7IePaB+JgMuJ/BNcaApy01h5VNoPy4S1hmkm7kdlFpwRQXzat0UgZPrD70vv9M4DykVKoqQnjEbaxj/l6WvShJ+/z31i/j0NL3T+3bOrBy2k+csydoJ09U/a/SQ6cDaY/mRktmEqt/KdBxR75kW0V/M6VGk6sSb07sq/0+OaKpVsQEMU38DgIGeU4moKmrjeTE4UAgikhWLkH8= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Oct 12, 2026 at 08:51:10PM +0200, David Hildenbrand (Arm) wrote: > On 10/12/26 20:48, Lorenzo Stoakes (ARM) wrote: > > On Mon, Oct 12, 2026 at 08:39:35PM +0200, David Hildenbrand (Arm) wrote: > >> On 10/12/26 20:35, Lorenzo Stoakes (ARM) wrote: > >>> > >>> That gets removed. > >>> > >>> > >>> I mean we do that in a subsequent commit, I think even the next one? > >>> > >>> > >>> > >>> Yeah, but to do that the code would now be something like: > >>> > >>> vma_flags_t masked = flags; > >>> > >>> /* > >>> * vma_flags_is_mm_managed() tests VMA_IO_BIT, which will be removed > >>> * in the next commit. > >>> */ > >>> vma_flags_clear(&flags, VMA_IO_BIT); > >>> if (!vma_flags_is_mm_managed(masked)) { > >>> ... > >>> } > >>> > >>> Is that really worth it? > >>> > >>> I don't think there's really too much confusion intra-patch about that is there? > >> > >> I would do it as above (- the comment, as that is the next patch indeed) and > >> only remove the vma_flags_clear() in the next patch. > >> > >> But in any case, you should spell out that this is only temporary in the patch > >> description :) > > > > And then there's a 'masked' variable that is unused? > > > > You need to have two vma_flags_t variables to be able both clear VMA_IO_BIT > > and use vma_flags_is_mm_managed(). > > > > So the change would have to be > > > > + vma_flags_t masked = *flags; > > + > > + vma_flags_clear(&flags, VMA_IO_BIT); > > + if (!vma_flags_is_mm_managed(&masked)) { > > + ... > > + } > > > > Then: > > > > - vma_flags_t masked = *flags; > > - > > - vma_flags_clear(&flags, VMA_IO_BIT); > > - if (!vma_flags_is_mm_managed(&masked)) { > > + if (!vma_flags_is_mm_managed(flags)) { > > ... > > } > > > > Which doesn't really seem worth it for somebody who is confused between two > > patches mid-series. > > > > But if you feel strongly I can make the change like that? > > Whatever you prefer. Most important thing for me was finding it in the next > patch and being pleasantly surprised ;) I'd rather not then! It was always intended that way, this was all part of a careful dance to ensure correct behaviour right up until the point where we enforce that VMA_IO_BIT is only set when appropriate. I can update the commit message to reflect it. -- Cheers, Lorenzo