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Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Alexander Viro , Christian Brauner , Jan Kara , Matthew Wilcox Subject: Re: [RFC PATCH v2 2/3] mm: secretmem: convert to .mmap_prepare() hook Message-ID: References: <987b620592ad6a472281039c07cc1d67e48d864f.1746116777.git.lorenzo.stoakes@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <987b620592ad6a472281039c07cc1d67e48d864f.1746116777.git.lorenzo.stoakes@oracle.com> X-Rspam-User: X-Rspamd-Queue-Id: 0B326100006 X-Rspamd-Server: rspam04 X-Stat-Signature: he74y5q5d7oowkrnposnkxsijmygzyz5 X-HE-Tag: 1746598185-999809 X-HE-Meta: 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 tPKUQRXD BRAap01iEnVAy1UO4LXNvpaiT4StN9OKrdIwlaDmNWaT6woaa3f7n41GwKLknTG4ayBNNzNo3TYrG4KUzK0N2oYxo8fkiIWlyrPD+rGdVdxR16XxBYp2VGs9fhH/0WiYgG5Bi4QuXB3UBKLwIrtmg3J18i/mkvYu/edKXrGUDNAJKIGyVS8viMdhWhnLq2+HZqzBS5RHEGsDjjPFxlm9iPYiPcekKzzOpSGy7dZgQo6MlXZGoW/eFTnU9ZiucZZchiyQkgck0EEMaGlNwMzfuDZ4Guh3gxgCZl3v6K0F2dRog94BCfT+u15HUzWPZBDLXRo82UjbA8l/V4FSxO0k2d3J+DqpoBnJggXWF 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: On Thu, May 01, 2025 at 06:25:28PM +0100, Lorenzo Stoakes wrote: > Secretmem has a simple .mmap() hook which is easily converted to the new > .mmap_prepare() callback. > > Importantly, it's a rare instance of an driver that manipulates a VMA which > is mergeable (that is, not a VM_SPECIAL mapping) while also adjusting VMA > flags which may adjust mergeability, meaning the retry merge logic might > impact whether or not the VMA is merged. > > By using .mmap_prepare() there's no longer any need to retry the merge > later as we can simply set the correct flags from the start. > > This change therefore allows us to remove the retry merge logic in a > subsequent commit. > > Signed-off-by: Lorenzo Stoakes Acked-by: Mike Rapoport (Microsoft) > --- > mm/secretmem.c | 14 +++++++------- > 1 file changed, 7 insertions(+), 7 deletions(-) > > diff --git a/mm/secretmem.c b/mm/secretmem.c > index 1b0a214ee558..f98cf3654974 100644 > --- a/mm/secretmem.c > +++ b/mm/secretmem.c > @@ -120,18 +120,18 @@ static int secretmem_release(struct inode *inode, struct file *file) > return 0; > } > > -static int secretmem_mmap(struct file *file, struct vm_area_struct *vma) > +static int secretmem_mmap_prepare(struct vm_area_desc *desc) > { > - unsigned long len = vma->vm_end - vma->vm_start; > + unsigned long len = desc->end - desc->start; > > - if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0) > + if ((desc->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0) > return -EINVAL; > > - if (!mlock_future_ok(vma->vm_mm, vma->vm_flags | VM_LOCKED, len)) > + if (!mlock_future_ok(desc->mm, desc->vm_flags | VM_LOCKED, len)) > return -EAGAIN; > > - vm_flags_set(vma, VM_LOCKED | VM_DONTDUMP); > - vma->vm_ops = &secretmem_vm_ops; > + desc->vm_flags |= VM_LOCKED | VM_DONTDUMP; > + desc->vm_ops = &secretmem_vm_ops; > > return 0; > } > @@ -143,7 +143,7 @@ bool vma_is_secretmem(struct vm_area_struct *vma) > > static const struct file_operations secretmem_fops = { > .release = secretmem_release, > - .mmap = secretmem_mmap, > + .mmap_prepare = secretmem_mmap_prepare, > }; > > static int secretmem_migrate_folio(struct address_space *mapping, > -- > 2.49.0 > -- Sincerely yours, Mike.