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

From: Waiman Long
Date: Tue Feb 19 2013 - 14:07:57 EST

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@xxxxxx>
fs/dcache.c | 3 +--
1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index b1487e2..0e911fc 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2547,6 +2547,7 @@ 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,
@@ -2573,9 +2574,7 @@ 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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