[PATCH v2 4/4] dcache: don't need to take d_lock in prepend_path()

Waiman Long Waiman.Long at hp.com
Fri Apr 5 10:57:41 MDT 2013

The d_lock was used in prepend_path() to protect dentry->d_name from
being changed under the hood. As the caller of prepend_path() has
to take the rename_lock before calling into it, there is no chance
that d_name will be changed. The d_lock lock is only needed when the
rename_lock is not taken.

Signed-off-by: Waiman Long <Waiman.Long at hp.com>
 fs/dcache.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 9477d80..e3d6543 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2529,6 +2529,7 @@ static int prepend_name(char **buffer, int *buflen, struct qstr *name)
  * @buflen: pointer to buffer length
  * Caller holds the rename_lock.
+ * There is no need to lock the dentry as its name cannot be changed.
 static int prepend_path(const struct path *path,
 			const struct path *root,
@@ -2555,9 +2556,7 @@ static int prepend_path(const struct path *path,
 		parent = dentry->d_parent;
-		spin_lock(&dentry->d_lock);
 		error = prepend_name(buffer, buflen, &dentry->d_name);
-		spin_unlock(&dentry->d_lock);
 		if (!error)
 			error = prepend(buffer, buflen, "/", 1);
 		if (error)

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