linux-kernel - [PATCH 21/41] mm/mmap: write-lock VMAs affected by VMA expansion

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Date:   Mon,  9 Jan 2023 12:53:16 -0800
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     akpm@...ux-foundation.org
Cc:     michel@...pinasse.org, jglisse@...gle.com, mhocko@...e.com,
        vbabka@...e.cz, hannes@...xchg.org, mgorman@...hsingularity.net,
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        peterz@...radead.org, ldufour@...ux.ibm.com,
        laurent.dufour@...ibm.com, paulmck@...nel.org, luto@...nel.org,
        songliubraving@...com, peterx@...hat.com, david@...hat.com,
        dhowells@...hat.com, hughd@...gle.com, bigeasy@...utronix.de,
        kent.overstreet@...ux.dev, punit.agrawal@...edance.com,
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        arjunroy@...gle.com, soheil@...gle.com, hughlynch@...gle.com,
        leewalsh@...gle.com, posk@...gle.com, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org,
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        surenb@...gle.com
Subject: [PATCH 21/41] mm/mmap: write-lock VMAs affected by VMA expansion

vma_expand changes VMA boundaries and might result in freeing an adjacent
VMA. Write-lock affected VMAs to prevent concurrent page faults.

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

diff --git a/mm/mmap.c b/mm/mmap.c
index 1e2154137631..ff02cb51e7e7 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -544,6 +544,7 @@ inline int vma_expand(struct ma_state *mas, struct vm_area_struct *vma,
 	if (mas_preallocate(mas, vma, GFP_KERNEL))
 		goto nomem;
 
+	vma_write_lock(vma);
 	vma_adjust_trans_huge(vma, start, end, 0);
 
 	if (file) {
@@ -590,6 +591,7 @@ inline int vma_expand(struct ma_state *mas, struct vm_area_struct *vma,
 	}
 
 	if (remove_next) {
+		vma_write_lock(next);
 		if (file) {
 			uprobe_munmap(next, next->vm_start, next->vm_end);
 			fput(file);
-- 
2.39.0