On 7/29/26 18:48, Lorenzo Stoakes (ARM) wrote: > This function provides the anonymous equivalent of linear_page_index(), > instead offsetting based on the anonymous page offset of the VMA. > > It is valid only for anonymous or MAP_PRIVATE file-backed mappings. It must > not be called for shared file-backed mappings. > > For pure anon VMAs, this will be equal to linear_page_index(). > > Assert that both of these invariants are true In linear_anon_page_index() > and implement the algorithm in __linear_anon_page_index(). > > Note that MAP_PRIVATE-/dev/zero mappings will satisfy vma_is_anonymous() > but not fulfill this invariant, so when asserting this we check > vma->vm_file to account for this. > > We do not update callsites yet, so no functional change intended. > > Also const-ify vma_is_anonymous() to make it compatible with the > const-ified linear_anon_page_index(). > > VMA userland tests are also updated accordingly.
In general looks good, some comments below. > > Signed-off-by: Lorenzo Stoakes (ARM) <[email protected]> > --- > include/linux/mm.h | 2 +- > include/linux/pagemap.h | 42 > +++++++++++++++++++++++++++++++++++++++++ > tools/testing/vma/include/dup.h | 25 +++++++++++++++++++++++- > 3 files changed, 67 insertions(+), 2 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index df78847f5f07..64214191e7c6 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1556,7 +1556,7 @@ static inline void vma_desc_set_anonymous(struct > vm_area_desc *desc) > desc->vm_ops = NULL; > } > > -static inline bool vma_is_anonymous(struct vm_area_struct *vma) > +static inline bool vma_is_anonymous(const struct vm_area_struct *vma) > { > return !vma->vm_ops; > } > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h > index c6fc783aaee5..259177544b03 100644 > --- a/include/linux/pagemap.h > +++ b/include/linux/pagemap.h > @@ -1101,6 +1101,48 @@ static inline pgoff_t linear_page_index(const struct > vm_area_struct *vma, > return pgoff; > } > > +static inline pgoff_t __linear_anon_page_index(const struct vm_area_struct > *vma, > + const unsigned long address) Nit Usual "two tab" comment (same below) :) > +{ > + pgoff_t pgoff; > + > + pgoff = linear_page_delta(vma, address); > + pgoff += vma_start_anon_pgoff(vma); I'd simply do return vma_start_anon_pgoff(vma) + linear_page_delta(vma, address); > + return pgoff; > +} > + > +/** > + * linear_anon_page_index() - Determine the absolute anonymous page offset of > + * @address within @vma. > + * @vma: An anonymous or MAP_PRIVATE file-backed VMA in which @address > resides. > + * @address: The address whose absolute page offset is required. > + * > + * This returns the anonymous page offset of @address, which is the page > offset > + * the address possessed at the time the VMA was first faulted. > + * > + * For anonymous mappings, this returns the same value as > linear_page_index(). > + * > + * For MAP_PRIVATE file-backed mappings, this returns the anonymous page > offset > + * of @address, which is the page offset the address possessed at the time > the > + * VMA was first faulted. > + * > + * It is not valid to call this function for shared file-backed mappings. > + * > + * Returns: The absolute anonymous page offset of @address within @vma. > + */ > +static inline pgoff_t linear_anon_page_index(const struct vm_area_struct > *vma, > + const unsigned long address) Dito. > +{ > + const pgoff_t pgoff = __linear_anon_page_index(vma, address); > + > + VM_WARN_ON_ONCE(vma_test(vma, VMA_SHARED_BIT)); Could we test or COW mappings instead? VM_WARN_ON_ONCE(!is_cow_mapping(vma)); Because we must never have anon folios is non-cow mappings. [...] > +static inline pgoff_t __linear_anon_page_index(const struct vm_area_struct > *vma, > + const unsigned long address) > +{ > + pgoff_t pgoff; > + > + pgoff = linear_page_delta(vma, address); > + pgoff += vma_start_anon_pgoff(vma); > + return pgoff; > +} Same comment as above. -- Cheers, David
