linux-kernel - [PATCH 1/1] mm/nommu: remove unnecessary VMA locking

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Message-ID: <20230301190457.1498985-1-surenb@google.com>
Date:   Wed,  1 Mar 2023 11:04:57 -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, paulmck@...nel.org,
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        kent.overstreet@...ux.dev, punit.agrawal@...edance.com,
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        gthelen@...gle.com, gurua@...gle.com, arjunroy@...gle.com,
        soheil@...gle.com, leewalsh@...gle.com, posk@...gle.com,
        michalechner92@...glemail.com, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        Suren Baghdasaryan <surenb@...gle.com>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>
Subject: [PATCH 1/1] mm/nommu: remove unnecessary VMA locking

Since CONFIG_PER_VMA_LOCK depends on CONFIG_MMU, the changes in nommu
are not needed. Remove them.

Fixes: bad94decd6a4 ("mm: write-lock VMAs before removing them from VMA tree")
Reported-by: Hyeonggon Yoo <42.hyeyoo@...il.com>
Link: https://lore.kernel.org/all/Y%2F8CJQGNuMUTdLwP@localhost/
Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
---
Fix cleanly applies over mm-unstable, SHA in "Fixes" is from that tree.

 mm/nommu.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/mm/nommu.c b/mm/nommu.c
index 2ab162d773e2..57ba243c6a37 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -588,7 +588,6 @@ static int delete_vma_from_mm(struct vm_area_struct *vma)
 		       current->pid);
 		return -ENOMEM;
 	}
-	vma_start_write(vma);
 	cleanup_vma_from_mm(vma);
 
 	/* remove from the MM's tree and list */
@@ -1520,10 +1519,6 @@ void exit_mmap(struct mm_struct *mm)
 	 */
 	mmap_write_lock(mm);
 	for_each_vma(vmi, vma) {
-		/*
-		 * No need to lock VMA because this is the only mm user and no
-		 * page fault handled can race with it.
-		 */
 		cleanup_vma_from_mm(vma);
 		delete_vma(mm, vma);
 		cond_resched();
-- 
2.40.0.rc0.216.gc4246ad0f0-goog