* Peng Zhang <zhangpeng.00@xxxxxxxxxxxxx> [230425 07:05]:
> Let mtree_alloc_range() and mtree_alloc_rrange() use mas_empty_area()
> and mas_empty_area_rev() respectively for allocation to reduce code
> redundancy. And after doing this, we don't need to maintain two logically
> identical codes to improve maintainability.
>
> In fact, mtree_alloc_range/rrange() has some bugs. For example, when
> dealing with min equals to max (mas_empty_area/area_rev() has been fixed),
> the allocation will fail.
> There are still some other bugs in it, I saw it with my naked eyes, but
> I didn't test it, for example:
> When mtree_alloc_range()->mas_alloc()->mas_awalk(), we set mas.index = min,
> mas.last = max - size. However, mas_awalk() requires mas.index = min,
> mas.last = max, which may lead to allocation failures.
Please don't re-state code in your commit messages.
Try to focus on what you did, and not why.
ie: Aligned mtree_alloc_range() to use the same internal function as
mas_empty_area().
>
> Right now no users are using these two functions so the bug won't trigger,
> but this might trigger in the future.
>
> Also use mas_store_gfp() instead of mas_fill_gap() as I don't see any
> difference between them.
Yeah, evolution of the code converged on the same design. Thanks for
seeing this.
>
> After doing this, we no longer need the three functions
> mas_fill_gap(), mas_alloc(), and mas_rev_alloc().
Let's just drop mtree_alloc_range() and mtree_alloc_rrange() and
whatever else you found here. They were planned to simplify the mmap
code allocations, but since there would need to be arch involvement
(coloring, etc) and alignment, etc; it is better to leave this job to
the mm code itself.
>
> Fixes: 54a611b60590 ("Maple Tree: add new data structure")
> Signed-off-by: Peng Zhang <zhangpeng.00@xxxxxxxxxxxxx>
> ---
> lib/maple_tree.c | 45 ++++++++++++---------------------------------
> 1 file changed, 12 insertions(+), 33 deletions(-)
>
> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> index aa55c914818a0..294d4c8668323 100644
> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -6362,32 +6362,20 @@ int mtree_alloc_range(struct maple_tree *mt, unsigned long *startp,
> {
> int ret = 0;
>
> - MA_STATE(mas, mt, min, max - size);
> + MA_STATE(mas, mt, 0, 0);
> if (!mt_is_alloc(mt))
> return -EINVAL;
>
> if (WARN_ON_ONCE(mt_is_reserved(entry)))
> return -EINVAL;
>
> - if (min > max)
> - return -EINVAL;
> -
> - if (max < size)
> - return -EINVAL;
> -
> - if (!size)
> - return -EINVAL;
> -
> mtree_lock(mt);
> -retry:
> - mas.offset = 0;
> - mas.index = min;
> - mas.last = max - size;
> - ret = mas_alloc(&mas, entry, size, startp);
> - if (mas_nomem(&mas, gfp))
> - goto retry;
> -
> + ret = mas_empty_area(&mas, min, max, size);
> + if (!ret)
> + ret = mas_store_gfp(&mas, entry, gfp);
> mtree_unlock(mt);
> + if (!ret)
> + *startp = mas.index;
> return ret;
> }
> EXPORT_SYMBOL(mtree_alloc_range);
> @@ -6398,29 +6386,20 @@ int mtree_alloc_rrange(struct maple_tree *mt, unsigned long *startp,
> {
> int ret = 0;
>
> - MA_STATE(mas, mt, min, max - size);
> + MA_STATE(mas, mt, 0, 0);
> if (!mt_is_alloc(mt))
> return -EINVAL;
>
> if (WARN_ON_ONCE(mt_is_reserved(entry)))
> return -EINVAL;
>
> - if (min >= max)
> - return -EINVAL;
> -
> - if (max < size - 1)
> - return -EINVAL;
> -
> - if (!size)
> - return -EINVAL;
> -
> mtree_lock(mt);
> -retry:
> - ret = mas_rev_alloc(&mas, min, max, entry, size, startp);
> - if (mas_nomem(&mas, gfp))
> - goto retry;
> -
> + ret = mas_empty_area_rev(&mas, min, max, size);
> + if (!ret)
> + ret = mas_store_gfp(&mas, entry, gfp);
> mtree_unlock(mt);
> + if (!ret)
> + *startp = mas.index;
> return ret;
> }
> EXPORT_SYMBOL(mtree_alloc_rrange);
> --
> 2.20.1
>
