[PATCH v4 04/10] mm/mremap: cleanup post-processing stage of mremap
From: Lorenzo Stoakes <hidden>
Date: 2025-07-17 16:57:32
Also in:
linux-fsdevel, linux-mm, lkml
Subsystem:
memory management, memory mapping, the rest · Maintainers:
Andrew Morton, Liam R. Howlett, Lorenzo Stoakes, Linus Torvalds
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. Signed-off-by: Lorenzo Stoakes <redacted> Reviewed-by: Vlastimil Babka <redacted> --- mm/mremap.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-)
diff --git a/mm/mremap.c b/mm/mremap.c
index 60eb0ac8634b..53447761e55d 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; }
--
2.50.1