linux-kernel - [PATCH v4 2/4] mm: Use rwsem assertion macros for mmap

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Message-Id: <20231117145142.2378800-3-willy@infradead.org>
Date:   Fri, 17 Nov 2023 14:51:40 +0000
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Chandan Babu R <chandan.babu@...cle.com>,
        "Darrick J . Wong" <djwong@...nel.org>, linux-xfs@...r.kernel.org,
        Mateusz Guzik <mjguzik@...il.com>
Subject: [PATCH v4 2/4] mm: Use rwsem assertion macros for mmap_lock

This slightly strengthens our write assertion when lockdep is disabled.
It also downgrades us from BUG_ON to WARN_ON, but I think that's an
improvement.  I don't think dumping the mm_struct was all that valuable;
the call chain is what's important.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 include/linux/mmap_lock.h | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h
index 8d38dcb6d044..de9dc20b01ba 100644
--- a/include/linux/mmap_lock.h
+++ b/include/linux/mmap_lock.h
@@ -60,16 +60,14 @@ static inline void __mmap_lock_trace_released(struct mm_struct *mm, bool write)
 
 #endif /* CONFIG_TRACING */
 
-static inline void mmap_assert_locked(struct mm_struct *mm)
+static inline void mmap_assert_locked(const struct mm_struct *mm)
 {
-	lockdep_assert_held(&mm->mmap_lock);
-	VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm);
+	rwsem_assert_held(&mm->mmap_lock);
 }
 
-static inline void mmap_assert_write_locked(struct mm_struct *mm)
+static inline void mmap_assert_write_locked(const struct mm_struct *mm)
 {
-	lockdep_assert_held_write(&mm->mmap_lock);
-	VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm);
+	rwsem_assert_held_write(&mm->mmap_lock);
 }
 
 #ifdef CONFIG_PER_VMA_LOCK
-- 
2.42.0