linux-kernel - [PATCH v3 03/14] fs: aio: Remove redundant rcu_read_lock/unlock() in spin

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Message-Id: <20250916044735.2316171-4-dolinux.peng@gmail.com>
Date: Tue, 16 Sep 2025 12:47:24 +0800
From: pengdonglin <dolinux.peng@...il.com>
To: tj@...nel.org,
	tony.luck@...el.com,
	jani.nikula@...ux.intel.com,
	ap420073@...il.com,
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Cc: bigeasy@...utronix.de,
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	pengdonglin <dolinux.peng@...il.com>,
	pengdonglin <pengdonglin@...omi.com>
Subject: [PATCH v3 03/14] fs: aio: Remove redundant rcu_read_lock/unlock() in spin_lock

From: pengdonglin <pengdonglin@...omi.com>

Since commit a8bb74acd8efe ("rcu: Consolidate RCU-sched update-side function definitions")
there is no difference between rcu_read_lock(), rcu_read_lock_bh() and
rcu_read_lock_sched() in terms of RCU read section and the relevant grace
period. That means that spin_lock(), which implies rcu_read_lock_sched(),
also implies rcu_read_lock().

There is no need no explicitly start a RCU read section if one has already
been started implicitly by spin_lock().

Simplify the code and remove the inner rcu_read_lock() invocation.

Cc: Benjamin LaHaise <bcrl@...ck.org>
Signed-off-by: pengdonglin <pengdonglin@...omi.com>
Signed-off-by: pengdonglin <dolinux.peng@...il.com>
---
 fs/aio.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 7fc7b6221312..e3f9a5a391b5 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -359,15 +359,14 @@ static int aio_ring_mremap(struct vm_area_struct *vma)
 	int i, res = -EINVAL;
 
 	spin_lock(&mm->ioctx_lock);
-	rcu_read_lock();
-	table = rcu_dereference(mm->ioctx_table);
+	table = rcu_dereference_check(mm->ioctx_table, lockdep_is_held(&mm->ioctx_lock));
 	if (!table)
 		goto out_unlock;
 
 	for (i = 0; i < table->nr; i++) {
 		struct kioctx *ctx;
 
-		ctx = rcu_dereference(table->table[i]);
+		ctx = rcu_dereference_check(table->table[i], lockdep_is_held(&mm->ioctx_lock));
 		if (ctx && ctx->aio_ring_file == file) {
 			if (!atomic_read(&ctx->dead)) {
 				ctx->user_id = ctx->mmap_base = vma->vm_start;
@@ -378,7 +377,6 @@ static int aio_ring_mremap(struct vm_area_struct *vma)
 	}
 
 out_unlock:
-	rcu_read_unlock();
 	spin_unlock(&mm->ioctx_lock);
 	return res;
 }
-- 
2.34.1