* Suren Baghdasaryan <surenb@xxxxxxxxxx> [240503 18:29]:
> On Fri, Apr 26, 2024 at 10:15 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
> >
> > Liam asked me if we could do away with the "bool *mmap_locked"
> > parameter, and the problem is that some architctures don't support
> > CONFIG_PER_VMA_LOCK yet. But we can abstract it ... something like this
> > maybe?
> >
> > (not particularly proposing this for inclusion; just wrote it and want
> > to get it out of my tree so I can get back to other projects. If anyone
> > wants it, they can test it and submit it for inclusion and stick my
> > S-o-B on it)
>
> I went through all uses of vma_end_read() to convince myself this is
> safe with CONFIG_PER_VMA_LOCK=n and the change seems fine from
> correctness POV. However the fact that in this configuration
> lock_vma_under_mmap_lock()==NOP and vma_end_read()==mmap_read_unlock()
> does not feel right to me. Current code is more explicit about which
> lock is held and I think it's easier to understand.
> A new interface like below might be a bit better but I'm not sure if
> it's worth it:
>
...
We could do something like we do in the release_fault_lock(), but
without using the FAULT flag..
/* Naming is hard. */
static inline void release_vma_modification_lock(
struct vm_area_struct *vma)
{
#ifdef CONFIG_PER_VMA_LOCK
if (rwsem_is_locked(&vma->vm_lock->lock))
vma_end_read(vma);
else
mmap_read_unlock(vma->vm_mm);
#else
mmap_read_unlock(vma->vm_mm);
#endif
}
