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freedreno@lists.freedesktop.org, linux-tegra@vger.kernel.org, kvm@vger.kernel.org, Russell King References: <20260710-b4-pre-scalable-cow-v2-0-2a5aa403d977@kernel.org> <20260710-b4-pre-scalable-cow-v2-15-2a5aa403d977@kernel.org> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/10/26 22:16, Lorenzo Stoakes wrote: > Add comments with ASCII diagrams to describe what we're doing, avoid > dubious use of PHYS_PFN(), and use vma_start_pgoff(). > > The most complicated scenario represented here is vmg->__adjust_next_start > - when this is set, vmg->[start, end] actually indicate the range to be > retained, so take special care to describe this accurately. > > No functional change intended. > > Reviewed-by: Pedro Falcato > Reviewed-by: Gregory Price > Signed-off-by: Lorenzo Stoakes Reviewed-by: Vlastimil Babka (SUSE) > --- > mm/vma.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++---- > 1 file changed, 47 insertions(+), 4 deletions(-) > > diff --git a/mm/vma.c b/mm/vma.c > index 084afdf37385..7265a054cfa3 100644 > --- a/mm/vma.c > +++ b/mm/vma.c > @@ -704,11 +704,54 @@ static void vmg_adjust_set_range(struct vma_merge_struct *vmg) > pgoff_t pgoff; > > if (vmg->__adjust_middle_start) { > - adjust = vmg->middle; > - pgoff = adjust->vm_pgoff + PHYS_PFN(vmg->end - adjust->vm_start); > + /* > + * vmg->start vmg->end > + * | | > + * v merge v > + * <-------------> > + * delta > + * <------> > + * |------|----------------| > + * | prev | middle | > + * |------|----------------| > + * ^ > + * | > + * middle->vm_start > + */ > + struct vm_area_struct *middle = vmg->middle; > + const unsigned long delta = vmg->end - middle->vm_start; > + > + pgoff = vma_start_pgoff(middle) + (delta >> PAGE_SHIFT); > + adjust = middle; > } else if (vmg->__adjust_next_start) { > - adjust = vmg->next; > - pgoff = adjust->vm_pgoff - PHYS_PFN(adjust->vm_start - vmg->end); > + /* > + * Originally: > + * > + * vmg->start vmg->end > + * | | > + * v merge v > + * <------------> > + * . . > + * merge_existing_range() updates to: > + * . . > + * vmg->start vmg->end . > + * | | . > + * v retain v . > + * <----------> . > + * delta . > + * <-----> . > + * |----------------|------| > + * | middle | next | > + * |----------------|------| > + * ^ > + * | > + * next->vm_start > + */ > + struct vm_area_struct *next = vmg->next; > + const unsigned long delta = next->vm_start - vmg->end; > + > + pgoff = vma_start_pgoff(next) - (delta >> PAGE_SHIFT); > + adjust = next; > } else { > return; > } >