From e49e76c20ba10e04b257f522e5a086db43d8f1c1 Mon Sep 17 00:00:00 2001 From: Lorenzo Stoakes Date: Thu, 17 Jul 2025 17:55:54 +0100 Subject: [PATCH] mm/mremap: cleanup post-processing stage of mremap 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 whether an error occurred - explicitly check for this. No functional change intended. Link: https://lkml.kernel.org/r/ebb8f29650b8e343fe98fefc67b3a61a24d1e0f1.1752770784.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes Reviewed-by: Vlastimil Babka Cc: Al Viro Cc: Christian Brauner Cc: Jan Kara Cc: Jann Horn Cc: Liam Howlett Cc: Peter Xu Cc: Rik van Riel Signed-off-by: Andrew Morton --- mm/mremap.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) diff --git a/mm/mremap.c b/mm/mremap.c index 60eb0ac8634b2..53447761e55df 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 to) +{ + struct mm_struct *mm = current->mm; + + userfaultfd_unmap_complete(mm, vrm->uf_unmap_early); + mremap_userfaultfd_complete(vrm->uf, vrm->addr, to, 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; } -- 2.47.2