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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v3 1/3] drivers/char/mem: eliminate unnecessary use of success_hook Message-ID: <2026060313-tutor-trophy-e394@gregkh> References: <010579cca6787cf7bb057ab1f7228978b10601c8.1780397980.git.ljs@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <010579cca6787cf7bb057ab1f7228978b10601c8.1780397980.git.ljs@kernel.org> X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 923924000C X-Stat-Signature: e7wriwaq6kbfjjm8cbqabakhfgewohoa X-Rspam-User: X-HE-Tag: 1780503986-662387 X-HE-Meta: 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 +wWWmGUV Y2ZDNprVly66zpo1oR9GhAFtP0UwE1gUGmldRaBdjiQaY7maWFuKwUwhtsKtOp1ZZgcWZ2L2G3ri/HuPp69MqQ++M7R5kafDpaDmB+b0dZym2TV/7uhHcjlvr1OXocxLUusMyOz10Ag4pkn73V+ffPdV49dMIvBoOl3/NDUUnCkRP1Z2tEAI2dwGkeRlN2u0kOmJb43gtt+65OYAg1zCY80TLVCW65bPyBhr+YUy6HNy4Rpn6XlQd9ykwa9agFxGVk/QCuJCv5daC434OGl/9pc5bhV75X8iSbbKCqLxyiWvoZITZNb2Y7KqRBOjQ+HiMddTf8G1k15/uubJxTdNvWSAZH/40KVWKc018r/Gx289mFVab26bCJOxmfi2c7a9CevxcLLtPuwwrgRmpux994muIyPU3RfMJX+Ubn0guPyYt4EjDMd9E43xRYjuXqP3cHd/4sui3YV78+as= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jun 02, 2026 at 12:06:25PM +0100, Lorenzo Stoakes wrote: > /dev/zero, uniquely, marks memory mapped there as anonymous. This is > currently achieved using the mmap_action->success_hook. > > However this hook circumvents the abstraction of VMA initialisation so > it's preferable to do things a different way. > > To achieve this, this patch firstly defaults the VMA descriptor's vm_ops > field to the dummy VMA operations, which is what file-backed VMAs default > this field to. > > That way, we can detect whether a driver sets this field to NULL in order > to mark it anonymous. > > We then introduce vma_desc_set_anonymous() to do this explicitly, and > invoke it in mmap_zero_prepare(). > > This way, any driver which does not explicitly set desc->vm_ops, retains > the dummy vm_ops as they would previously. > > We also update set_vma_user_defined_fields() to make clear that we are > either setting vma->vm_ops to what is provided by the driver (or > defaulting to dummy_vm_ops if not set), or setting the VMA anonymous. > > This lays the groundwork for removing the success hook. > > Signed-off-by: Lorenzo Stoakes > Acked-by: David Hildenbrand (Arm) Acked-by: Greg Kroah-Hartman