}
#endif /* __ARCH_WANT_SYS_OLD_MMAP */
+static bool vm_ops_needs_writenotify(const struct vm_operations_struct *vm_ops)
+{
+ return vm_ops && (vm_ops->page_mkwrite || vm_ops->pfn_mkwrite);
+}
+
+static bool vma_is_shared_writable(struct vm_area_struct *vma)
+{
+ return (vma->vm_flags & (VM_WRITE | VM_SHARED)) ==
+ (VM_WRITE | VM_SHARED);
+}
+
+static bool vma_fs_can_writeback(struct vm_area_struct *vma)
+{
+ /* No managed pages to writeback. */
+ if (vma->vm_flags & VM_PFNMAP)
+ return false;
+
+ return vma->vm_file && vma->vm_file->f_mapping &&
+ mapping_can_writeback(vma->vm_file->f_mapping);
+}
+
+/*
+ * Does this VMA require the underlying folios to have their dirty state
+ * tracked?
+ */
+bool vma_needs_dirty_tracking(struct vm_area_struct *vma)
+{
+ /* Only shared, writable VMAs require dirty tracking. */
+ if (!vma_is_shared_writable(vma))
+ return false;
+
+ /* Does the filesystem need to be notified? */
+ if (vm_ops_needs_writenotify(vma->vm_ops))
+ return true;
+
+ /*
+ * Even if the filesystem doesn't indicate a need for writenotify, if it
+ * can writeback, dirty tracking is still required.
+ */
+ return vma_fs_can_writeback(vma);
+}
+
/*
* Some shared mappings will want the pages marked read-only
* to track write events. If so, we'll downgrade vm_page_prot
*/
int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot)
{
- vm_flags_t vm_flags = vma->vm_flags;
- const struct vm_operations_struct *vm_ops = vma->vm_ops;
-
/* If it was private or non-writable, the write bit is already clear */
- if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
+ if (!vma_is_shared_writable(vma))
return 0;
/* The backer wishes to know when pages are first written to? */
- if (vm_ops && (vm_ops->page_mkwrite || vm_ops->pfn_mkwrite))
+ if (vm_ops_needs_writenotify(vma->vm_ops))
return 1;
/* The open routine did something to the protections that pgprot_modify
* won't preserve? */
if (pgprot_val(vm_page_prot) !=
- pgprot_val(vm_pgprot_modify(vm_page_prot, vm_flags)))
+ pgprot_val(vm_pgprot_modify(vm_page_prot, vma->vm_flags)))
return 0;
/*
if (userfaultfd_wp(vma))
return 1;
- /* Specialty mapping? */
- if (vm_flags & VM_PFNMAP)
- return 0;
-
/* Can the mapping track the dirty pages? */
- return vma->vm_file && vma->vm_file->f_mapping &&
- mapping_can_writeback(vma->vm_file->f_mapping);
+ return vma_fs_can_writeback(vma);
}
/*