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[250904 13:51]: > On Thu, Sep 4, 2025 at 10:42=E2=80=AFAM David Hildenbrand wrote: > > > > On 04.09.25 19:33, Lorenzo Stoakes wrote: > > > On Thu, Sep 04, 2025 at 01:22:51PM -0400, Liam R. Howlett wrote: > > >>>> diff --git a/mm/mremap.c b/mm/mremap.c > > >>>> index e618a706aff5..793fad58302c 100644 > > >>>> --- a/mm/mremap.c > > >>>> +++ b/mm/mremap.c > > >>>> @@ -1040,7 +1040,7 @@ static unsigned long prep_move_vma(struct vm= a_remap_struct *vrm) > > >>>> * We'd prefer to avoid failure later on in do_munmap: > > >>>> * which may split one vma into three before unmapping. > > >>>> */ > > >>>> - if (current->mm->map_count >=3D sysctl_max_map_count - 3) > > >>>> + if (exceeds_max_map_count(current->mm, 4)) > > >>>> return -ENOMEM; > > >>> > > >>> In my version this would be: > > >>> > > >>> if (map_count_capacity(current->mm) < 4) > > >>> return -ENOMEM; > > >>> > > >> > > >> Someone could write map_count_capacity(current->mm) <=3D 4 and reint= roduce > > >> what this is trying to solve. And with the way it is written in thi= s > > >> patch, someone could pass in the wrong number. > > > > > > Right, but I think 'capacity' is pretty clear here, if the caller doe= s something > > > silly then that's on them... > > > > > >> > > >> I'm not sure this is worth doing. There are places we allow the cou= nt > > >> to go higher. > > > > > > ...But yeah, it's kinda borderline as to how useful this is. > > > > > > I _do_ however like the 'put map count in one place statically' rathe= r than > > > having a global, so a minimal version of this could be to just have a= helper > > > function that gets the sysctl_max_map_count, e.g.: > > > > > > if (current->mm->mmap_count >=3D max_map_count() - 3) > > > > I enjoy seeing sysctl_max_map_count hidden. But map_count_capacity() is > > even more readable, so I like it. > > > > I don't complete like the "capacity" term, but I cannot think of > > something better right now. Maybe something around "free" or > > "remaining", not sure. > > > > I also don't completely like "map_count" (I know, I know, we call it > > like that in structures), because it reminds me of the mapcount ... > > talking somehow about "vmas" would be quite clear. >=20 > Thanks David, my original implementation started with vma_limit() :). > Maybe something like vma_count_remaining() ? Yes, reducing this confusion would very much be helpful. In fact, if you put it in its own function we could change the actual name with lower impact. map_count vs mapcount is annoying. vma_headroom() ? additional_vma_space() ? Maybe David would like: remedy_vma_space() which would be !poison_vma_space().. that's pretty clear.. :) Cheers, Liam