Mastering Linux Kernel Development

Merging VMA regions

When a new VMA is mapped immediately before or after an existing VMA with identical access attributes and data from a file-backed memory region, it is more optimal to merge them into a single VMA structure. vma_merge() is a helper function that is invoked to merge surrounding VMAs with identical attributes:

struct vm_area_struct *vma_merge(struct mm_struct *mm,                        struct vm_area_struct *prev, unsigned long addr,                        unsigned long end, unsigned long vm_flags,                        struct anon_vma *anon_vma, struct file *file,                        pgoff_t pgoff, struct mempolicy *policy,                        struct vm_userfaultfd_ctx vm_userfaultfd_ctx){         pgoff_t pglen = (end - addr) >> PAGE_SHIFT;         struct vm_area_struct *area, *next;         int err;           ...         ...

*mm refers to the memory descriptor of the ...