* Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx> [240705 16:06]:
> 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()?
Yes, what we are doing is inlining the function call so that it can be
split to parts. So for reviewing, I just made it in-line.
>
> 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?
I don't see the validate_mm() call in do_vmi_align_munmap, it is called
in the vms_complete_munmap_vmas() function though.
>
> > +
> > + if (vma_iter_clear_gfp(&vmi, addr, end, GFP_KERNEL))
> > return -ENOMEM;
>
> Same here.
It would fail here, our count would be wrong.
>
> > +
> > + 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?
Yes. In the current function, the vmi points to prev when we are done
this dance - so I put it there.
>
> 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.
So this is about to change..
>
> > 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.
Yes, this is what I'm doing.
>
>
> > }
> >
> > /*
> > @@ -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
> >
> >
