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SubjectRe: [PATCH v4 11/66] mm/mmap: Use maple tree for unmapped_area{_topdown}
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* Vlastimil Babka <vbabka@suse.cz> [211215 11:43]:
> On 12/1/21 15:29, Liam Howlett wrote:
> > From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>
> >
> > The maple tree code was added to find the unmapped area in a previous
> > commit and was checked against what the rbtree returned, but the actual
> > result was never used. Start using the maple tree implementation and
> > remove the rbtree code.
>
> Nice cleanup. But...
>
> > Add kernel documentation comment for these functions.
> >
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
>
> >
> > /* Adjust search length to account for worst case alignment overhead */
> > length = info->length + info->align_mask;
> > if (length < info->length)
> > return -ENOMEM;
> >
> > - rcu_read_lock();
> > - mas_empty_area_rev(&mas, info->low_limit, info->high_limit - 1,
> > - length);
> > - rcu_read_unlock();
>
> Why is RCU locking being removed as part of this? Ditton in
> unmapped_area_topdown()

It is not needed with the mmap_lock() being used in the maple tree. But
I should either be consistent and keep it everywhere or not have it in
the earlier patch. I will fix this, maybe I should have left them in
everywhere.
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