On 7/7/25 07:27, Lorenzo Stoakes wrote:
> Separate out the uffd bits so it clear's what's happening.
>
> Don't bother setting vrm->mmap_locked after unlocking, because after this
> we are done anyway.
>
> The only time we drop the mmap lock is on VMA shrink, at which point
> vrm->new_len will be < vrm->old_len and the operation will not be performed
> anyway, so move this code out of the if (vrm->mmap_locked) block.
>
> All addresses returned by mremap() are page-aligned, so the
> offset_in_page() check on ret seems only to be incorrectly trying to detect
"incorrectly" to me implies there's a bug. But AFAIU there's not, so maybe
e.g. "inappropriately"?
> whether an error occurred - explicitly check for this.
>
> No functional change intended.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Just a nit:
> ---
> mm/mremap.c | 22 +++++++++++++---------
> 1 file changed, 13 insertions(+), 9 deletions(-)
>
> diff --git a/mm/mremap.c b/mm/mremap.c
> index 60eb0ac8634b..660bdb75e2f9 100644
> --- a/mm/mremap.c
> +++ b/mm/mremap.c
> @@ -1729,6 +1729,15 @@ static int check_prep_vma(struct vma_remap_struct *vrm)
> return 0;
> }
>
> +static void notify_uffd(struct vma_remap_struct *vrm, unsigned long ret)
"ret" not "res"? :) Or actually why not name it for what it is,
mremap_userfaultfd_complete() names the parameter "to". Maybe to_addr or
new_addr?
> +{
> + struct mm_struct *mm = current->mm;
> +
> + userfaultfd_unmap_complete(mm, vrm->uf_unmap_early);
> + mremap_userfaultfd_complete(vrm->uf, vrm->addr, ret, vrm->old_len);
> + userfaultfd_unmap_complete(mm, vrm->uf_unmap);
> +}
> +
> static unsigned long do_mremap(struct vma_remap_struct *vrm)
> {
> struct mm_struct *mm = current->mm;
> @@ -1754,18 +1763,13 @@ static unsigned long do_mremap(struct vma_remap_struct *vrm)
> res = vrm_implies_new_addr(vrm) ? mremap_to(vrm) : mremap_at(vrm);
>
> out:
> - if (vrm->mmap_locked) {
> + if (vrm->mmap_locked)
> mmap_write_unlock(mm);
> - vrm->mmap_locked = false;
> -
> - if (!offset_in_page(res) && vrm->mlocked && vrm->new_len > vrm->old_len)
> - mm_populate(vrm->new_addr + vrm->old_len, vrm->delta);
> - }
>
> - userfaultfd_unmap_complete(mm, vrm->uf_unmap_early);
> - mremap_userfaultfd_complete(vrm->uf, vrm->addr, res, vrm->old_len);
> - userfaultfd_unmap_complete(mm, vrm->uf_unmap);
> + if (!IS_ERR_VALUE(res) && vrm->mlocked && vrm->new_len > vrm->old_len)
> + mm_populate(vrm->new_addr + vrm->old_len, vrm->delta);
>
> + notify_uffd(vrm, res);
> return res;
> }
>
