This function provides the virtual equivalent of linear_page_index(), instead offsetting based on the virtual 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(). We implement the algorithm in __linear_virt_page_index(), which is provided for internal mm code that might be interacting with shared VMAs. In linear_virt_page_index() we assert that both of these invariants are true. 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_virt_page_index(). VMA userland tests are updated accordingly. 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 59b98cc60402..b6503b5f0010 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..c9c65ba60ab3 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_virt_page_index(const struct vm_area_struct *vma, + const unsigned long address) +{ + pgoff_t pgoff; + + pgoff = linear_page_delta(vma, address); + pgoff += vma_start_virt_pgoff(vma); + return pgoff; +} + +/** + * linear_virt_page_index() - Determine the absolute virtual 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 virtual 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 virtual 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 virtual page offset of @address within @vma. + */ +static inline pgoff_t linear_virt_page_index(const struct vm_area_struct *vma, + const unsigned long address) +{ + const pgoff_t pgoff = __linear_virt_page_index(vma, address); + + VM_WARN_ON_ONCE(vma_test(vma, VMA_SHARED_BIT)); + /* Account for MAP_PRIVATE-/dev/zero which is only semi-anonymous. */ + if (vma_is_anonymous(vma) && !vma->vm_file) + VM_WARN_ON_ONCE(pgoff != linear_page_index(vma, address)); + + return pgoff; +} + struct wait_page_key { struct folio *folio; int bit_nr; diff --git a/tools/testing/vma/include/dup.h b/tools/testing/vma/include/dup.h index 00d416d79ec1..0c74899abb33 100644 --- a/tools/testing/vma/include/dup.h +++ b/tools/testing/vma/include/dup.h @@ -1417,7 +1417,7 @@ static inline void vma_iter_set(struct vma_iterator *vmi, unsigned long addr) mas_set(&vmi->mas, addr); } -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; } @@ -1610,3 +1610,26 @@ static inline pgprot_t vma_get_page_prot(const struct vm_area_struct *vma) { return vma_flags_to_page_prot(vma->flags); } + +static inline pgoff_t __linear_virt_page_index(const struct vm_area_struct *vma, + const unsigned long address) +{ + pgoff_t pgoff; + + pgoff = linear_page_delta(vma, address); + pgoff += vma_start_virt_pgoff(vma); + return pgoff; +} + +static inline pgoff_t linear_virt_page_index(const struct vm_area_struct *vma, + const unsigned long address) +{ + const pgoff_t pgoff = __linear_virt_page_index(vma, address); + + VM_WARN_ON_ONCE(vma_test(vma, VMA_SHARED_BIT)); + /* Account for MAP_PRIVATE-/dev/zero which is only semi-anonymous. */ + if (vma_is_anonymous(vma) && !vma->vm_file) + VM_WARN_ON_ONCE(pgoff != linear_page_index(vma, address)); + + return pgoff; +} -- 2.55.0
