linux-kernel - [PATCH v2 02/15] mm/mmap: Introduce abort_munmap

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Date: Tue, 25 Jun 2024 15:11:32 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>
Cc: Suren Baghdasaryan <surenb@...gle.com>, Vlastimil Babka <vbabka@...e.cz>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Matthew Wilcox <willy@...radead.org>, sidhartha.kumar@...cle.com,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Bert Karwatzki <spasswolf@....de>, Jiri Olsa <olsajiri@...il.com>,
        linux-kernel@...r.kernel.org, Kees Cook <kees@...nel.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>
Subject: [PATCH v2 02/15] mm/mmap: Introduce abort_munmap_vmas()

Extract clean up of failed munmap() operations from
do_vmi_align_munmap().  This simplifies later patches in the series.

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 mm/mmap.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 28a46d9ddde0..d572e1ff8255 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2586,6 +2586,25 @@ struct vm_area_struct *vma_merge_extend(struct vma_iterator *vmi,
 			 vma->vm_userfaultfd_ctx, anon_vma_name(vma));
 }
 
+/*
+ * abort_munmap_vmas - Undo any munmap work and free resources
+ *
+ * Reattach detached vmas, free up maple tree used to track the vmas.
+ */
+static inline void abort_munmap_vmas(struct ma_state *mas_detach)
+{
+	struct vm_area_struct *vma;
+	int limit;
+
+	limit = mas_detach->index;
+	mas_set(mas_detach, 0);
+	/* Re-attach any detached VMAs */
+	mas_for_each(mas_detach, vma, limit)
+		vma_mark_detached(vma, false);
+
+	__mt_destroy(mas_detach->tree);
+}
+
 /*
  * do_vmi_align_munmap() - munmap the aligned region from @start to @end.
  * @vmi: The vma iterator
@@ -2740,11 +2759,7 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
 userfaultfd_error:
 munmap_gather_failed:
 end_split_failed:
-	mas_set(&mas_detach, 0);
-	mas_for_each(&mas_detach, next, end)
-		vma_mark_detached(next, false);
-
-	__mt_destroy(&mt_detach);
+	abort_munmap_vmas(&mas_detach);
 start_split_failed:
 map_count_exceeded:
 	validate_mm(mm);
-- 
2.43.0