On Thu, Jul 04, 2024 at 02:27:11PM GMT, Liam R. Howlett wrote:
> From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
>
> Open code the do_vmi_align_munmap() call so that it can be broken up
> later in the series.
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
> ---
> mm/mmap.c | 22 +++++++++++++++++++---
> 1 file changed, 19 insertions(+), 3 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index e9858ca8bbd4..f5b33de4e717 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2915,6 +2915,9 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
> struct vm_area_struct *next, *prev, *merge;
> pgoff_t pglen = len >> PAGE_SHIFT;
> unsigned long charged = 0;
> + struct vma_munmap_struct vms;
> + struct ma_state mas_detach;
> + struct maple_tree mt_detach;
> unsigned long end = addr + len;
> unsigned long merge_start = addr, merge_end = end;
> bool writable_file_mapping = false;
> @@ -2947,9 +2950,24 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
> /* Find the first overlapping VMA */
> vma = vma_find(&vmi, end);
> if (vma) {
> - if (do_vmi_align_munmap(&vmi, vma, mm, addr, end, uf, false))
> + mt_init_flags(&mt_detach, vmi.mas.tree->ma_flags & MT_FLAGS_LOCK_MASK);
> + mt_on_stack(mt_detach);
> + mas_init(&mas_detach, &mt_detach, /* addr = */ 0);
I'm guessing this is exactly equivalent (or equivalent enough for our purposes
here) to the MA_STATE() call in do_vmi_align_munmap()?
Checking the two against each other it seems that it is indeed.
> + init_vma_munmap(&vms, &vmi, vma, addr, end, uf, /* unlock = */ false);
> + if (vms_gather_munmap_vmas(&vms, &mas_detach))
> + return -ENOMEM;
In do_vmi_align_munmap() we also invoke vmalidate_mm(), why aren't we doing that
here?
> +
> + if (vma_iter_clear_gfp(&vmi, addr, end, GFP_KERNEL))
> return -ENOMEM;
Same here.
> +
> + vms_complete_munmap_vmas(&vms, &mas_detach);
> + next = vms.next;
> + prev = vms.prev;
> + vma_prev(&vmi);
I'm sure this is correct, but just to double-check - we want to set the VMI to
prev here right?
It might be worth adding a small cmoment saying '/* vmi now points at prev */'
or similar, I've found it can get quite hard to follow where the iterator is at
sometimes.
> vma = NULL;
> + } else {
> + next = vma_next(&vmi);
> + prev = vma_prev(&vmi);
But here we move forward to the next VMA and set this to next, then go back to
the _original_ one and this is prev?
Actually I guess if vma == NULL, next gets you to the next, and prev jumps back
to prev, with nothing between, and so that makes sense.
> }
>
> /*
> @@ -2962,8 +2980,6 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
> vm_flags |= VM_ACCOUNT;
> }
>
> - next = vma_next(&vmi);
> - prev = vma_prev(&vmi);
> if (vm_flags & VM_SPECIAL) {
> if (prev)
> vma_iter_next_range(&vmi);
> --
> 2.43.0
>
>
