From 0173db4f7f526540e2cc0a6a61e42771acd4c197 Mon Sep 17 00:00:00 2001 From: Lorenzo Stoakes Date: Wed, 22 Mar 2023 20:19:00 +0000 Subject: mm/mmap/vma_merge: init cleanup, be explicit about the non-mergeable case Rather than setting err = -1 and only resetting if we hit merge cases, explicitly check the non-mergeable case to make it abundantly clear that we only proceed with the rest if something is mergeable, default err to 0 and only update if an error might occur. Move the merge_prev, merge_next cases closer to the logic determining curr, next and reorder initial variables so they are more logically grouped. This has no functional impact. Link: https://lkml.kernel.org/r/99259fbc6403e80e270e1cc4612abbc8620b121b.1679516210.git.lstoakes@gmail.com Signed-off-by: Lorenzo Stoakes Reviewed-by: Vlastimil Babka Cc: David Hildenbrand Cc: Liam R. Howlett Cc: Matthew Wilcox (Oracle) Cc: Vernon Yang Signed-off-by: Andrew Morton --- mm/mmap.c | 47 ++++++++++++++++++++++------------------------- 1 file changed, 22 insertions(+), 25 deletions(-) (limited to 'mm/mmap.c') diff --git a/mm/mmap.c b/mm/mmap.c index 343859b1190d..6c326002184d 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -896,18 +896,18 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, struct vm_userfaultfd_ctx vm_userfaultfd_ctx, struct anon_vma_name *anon_name) { - pgoff_t pglen = (end - addr) >> PAGE_SHIFT; - pgoff_t vma_pgoff; struct vm_area_struct *curr, *next, *res; struct vm_area_struct *vma, *adjust, *remove, *remove2; - int err = -1; + struct vma_prepare vp; + pgoff_t vma_pgoff; + int err = 0; bool merge_prev = false; bool merge_next = false; bool vma_expanded = false; - struct vma_prepare vp; + unsigned long vma_start = addr; unsigned long vma_end = end; + pgoff_t pglen = (end - addr) >> PAGE_SHIFT; long adj_start = 0; - unsigned long vma_start = addr; validate_mm(mm); /* @@ -926,24 +926,14 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, else next = NULL; /* case 5 */ - /* - * By default, we return prev. Cases 3, 4, 8 will instead return next - * and cases 3, 8 will also update vma to point at next. - */ - res = vma = prev; - - /* Verify some invariant that must be enforced by the caller. */ - VM_WARN_ON(prev && addr <= prev->vm_start); - VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end)); - VM_WARN_ON(addr >= end); - if (prev) { vma_start = prev->vm_start; vma_pgoff = prev->vm_pgoff; + /* Can we merge the predecessor? */ - if (prev->vm_end == addr && mpol_equal(vma_policy(prev), policy) + if (addr == prev->vm_end && mpol_equal(vma_policy(prev), policy) && can_vma_merge_after(prev, vm_flags, anon_vma, file, - pgoff, vm_userfaultfd_ctx, anon_name)) { + pgoff, vm_userfaultfd_ctx, anon_name)) { merge_prev = true; vma_prev(vmi); } @@ -951,13 +941,22 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, /* Can we merge the successor? */ if (next && mpol_equal(policy, vma_policy(next)) && - can_vma_merge_before(next, vm_flags, - anon_vma, file, pgoff+pglen, + can_vma_merge_before(next, vm_flags, anon_vma, file, pgoff+pglen, vm_userfaultfd_ctx, anon_name)) { merge_next = true; } + if (!merge_prev && !merge_next) + return NULL; /* Not mergeable. */ + + res = vma = prev; remove = remove2 = adjust = NULL; + + /* Verify some invariant that must be enforced by the caller. */ + VM_WARN_ON(prev && addr <= prev->vm_start); + VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end)); + VM_WARN_ON(addr >= end); + /* Can we merge both the predecessor and the successor? */ if (merge_prev && merge_next && is_mergeable_anon_vma(prev->anon_vma, next->anon_vma, NULL)) { @@ -970,8 +969,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, if (!next->anon_vma) err = dup_anon_vma(prev, curr); } - } else if (merge_prev) { - err = 0; /* case 2 */ + } else if (merge_prev) { /* case 2 */ if (curr) { err = dup_anon_vma(prev, curr); if (end == curr->vm_end) { /* case 7 */ @@ -981,7 +979,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, adj_start = (end - curr->vm_start); } } - } else if (merge_next) { + } else { /* merge_next */ res = next; if (prev && addr < prev->vm_end) { /* case 4 */ vma_end = addr; @@ -997,7 +995,6 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, vma_start = addr; vma_end = next->vm_end; vma_pgoff = next->vm_pgoff; - err = 0; if (curr) { /* case 8 */ vma_pgoff = curr->vm_pgoff; remove = curr; @@ -1006,7 +1003,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, } } - /* Cannot merge or error in anon_vma clone */ + /* Error in anon_vma clone. */ if (err) return NULL; -- cgit