On 7/10/26 22:16, Lorenzo Stoakes wrote: > It's often useful to obtain the number of pages a given address lies at > within a VMA. > > Add linear_page_delta() to determine this and update linear_page_index() to > make use of it. > > Add comments to describe both linear_page_delta() and linear_page_index(). > > We refer the reader to the comment for vma_start_pgoff() so we don't > duplicate information about the meaning of a VMA's page offset, which is > also less likely to result in bitrot. > > No functional change intended. > > Reviewed-by: Ackerley Tng <[email protected]> > Reviewed-by: Gregory Price <[email protected]> > Reviewed-by: Pedro Falcato <[email protected]> > Signed-off-by: Lorenzo Stoakes <[email protected]>
Reviewed-by: Vlastimil Babka (SUSE) <[email protected]> > --- > include/linux/pagemap.h | 33 +++++++++++++++++++++++++++++++-- > 1 file changed, 31 insertions(+), 2 deletions(-) > > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h > index 2c3718d592d6..a950070b045f 100644 > --- a/include/linux/pagemap.h > +++ b/include/linux/pagemap.h > @@ -1063,11 +1063,40 @@ static inline pgoff_t folio_pgoff(const struct folio > *folio) > return folio->index; > } > > +/** > + * linear_page_delta() - Determine the relative page offset of @address > within > + * @vma. > + * @vma: The VMA in which @address resides. > + * @address: The address whose relative page offset is required. > + * > + * The result is identical for both file-backed and anonymous mappings and > + * simply determines how many pages @address lies from @vma->vm_start. > + * > + * Returns: The number of pages @address is offset by within @vma. > + */ > +static inline pgoff_t linear_page_delta(const struct vm_area_struct *vma, > + const unsigned long address) > +{ > + return (address - vma->vm_start) >> PAGE_SHIFT; > +} > + > +/** > + * linear_page_index() - Determine the absolute page offset of @address > within > + * @vma. > + * @vma: The VMA in which @address resides. > + * @address: The address whose absolute page offset is required. > + * > + * See the comment for vma_start_pgoff() for a description of what the page > + * offset signifies. > + * > + * Returns: The absolute page offset of @address within @vma. > + */ > static inline pgoff_t linear_page_index(const struct vm_area_struct *vma, > const unsigned long address) > { > pgoff_t pgoff; > - pgoff = (address - vma->vm_start) >> PAGE_SHIFT; > + > + pgoff = linear_page_delta(vma, address); > pgoff += vma->vm_pgoff; > return pgoff; > } > @@ -1219,7 +1248,7 @@ static inline vm_fault_t folio_lock_or_retry(struct > folio *folio, > void folio_wait_bit(struct folio *folio, int bit_nr); > int folio_wait_bit_killable(struct folio *folio, int bit_nr); > > -/* > +/* > * Wait for a folio to be unlocked. > * > * This must be called with the caller "holding" the folio, >
