linux-kernel - [PATCH v2 13/33] mm/mmap: move VMA locking before vma_adjust_trans

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Message-ID: <20230127194110.533103-14-surenb@google.com>
Date:   Fri, 27 Jan 2023 11:40:50 -0800
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     akpm@...ux-foundation.org
Cc:     michel@...pinasse.org, jglisse@...gle.com, mhocko@...e.com,
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        surenb@...gle.com
Subject: [PATCH v2 13/33] mm/mmap: move VMA locking before vma_adjust_trans_huge
 call

vma_adjust_trans_huge() modifies the VMA and such modifications should
be done after VMA is marked as being written. Therefore move VMA flag
modifications before vma_adjust_trans_huge() so that VMA is marked
before all these modifications.

Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
---
 mm/mmap.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 9efe13d36df7..7467d691e357 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2910,11 +2910,12 @@ static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *vma,
 		if (vma_iter_prealloc(vmi))
 			goto unacct_fail;
 
+		/* Set flags first to implicitly lock the VMA before updates */
+		vm_flags_set(vma, VM_SOFTDIRTY);
 		vma_adjust_trans_huge(vma, vma->vm_start, addr + len, 0);
 		init_vma_prep(&vp, vma);
 		vma_prepare(&vp);
 		vma->vm_end = addr + len;
-		vm_flags_set(vma, VM_SOFTDIRTY);
 		vma_iter_store(vmi, vma);
 
 		vma_complete(&vp, vmi, mm);
-- 
2.39.1