linux-kernel - [PATCH] dcache: use read_seqlock_excl() in d_set

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Date:	Wed, 13 Aug 2014 15:15:50 -0400
From:	Waiman Long <Waiman.Long@...com>
To:	Alexander Viro <viro@...iv.linux.org.uk>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Waiman Long <Waiman.Long@...com>
Subject: [PATCH] dcache: use read_seqlock_excl() in d_set_mounted()

The d_set_mounted() doesn't change anything in the filesystem other
than setting the DCACHE_MOUNTED flag in the mount point's dentry
which is protected by d_lock anyway. So we can safely replace
write_seqlock/write_sequnlock by read_seqlock_excl/read_sequnlock_excl.

Signed-off-by: Waiman Long <Waiman.Long@...com>
---
 fs/dcache.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 06f6585..bfdd8af 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1207,7 +1207,7 @@ int d_set_mounted(struct dentry *dentry)
 {
 	struct dentry *p;
 	int ret = -ENOENT;
-	write_seqlock(&rename_lock);
+	read_seqlock_excl(&rename_lock);
 	for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
 		/* Need exclusion wrt. check_submounts_and_drop() */
 		spin_lock(&p->d_lock);
@@ -1224,7 +1224,7 @@ int d_set_mounted(struct dentry *dentry)
 	}
  	spin_unlock(&dentry->d_lock);
 out:
-	write_sequnlock(&rename_lock);
+	read_sequnlock_excl(&rename_lock);
 	return ret;
 }
 
-- 
1.7.1

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