fs: name case update method
smpfs and ncpfs want to update a live dentry name in-place. Rather than
have them open code the locking, provide a documented dcache API.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
diff --git a/drivers/staging/smbfs/cache.c b/drivers/staging/smbfs/cache.c
index dbb9865..dbd2e1d 100644
--- a/drivers/staging/smbfs/cache.c
+++ b/drivers/staging/smbfs/cache.c
@@ -145,8 +145,8 @@
goto end_advance;
} else {
hashed = 1;
- memcpy((char *) newdent->d_name.name, qname->name,
- newdent->d_name.len);
+ /* dir i_mutex is locked because we're in readdir */
+ dentry_update_name_case(newdent, qname);
}
if (!newdent->d_inode) {
diff --git a/fs/dcache.c b/fs/dcache.c
index 6ee6bc4..814e5f4 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1589,6 +1589,33 @@
}
EXPORT_SYMBOL(d_rehash);
+/**
+ * dentry_update_name_case - update case insensitive dentry with a new name
+ * @dentry: dentry to be updated
+ * @name: new name
+ *
+ * Update a case insensitive dentry with new case of name.
+ *
+ * dentry must have been returned by d_lookup with name @name. Old and new
+ * name lengths must match (ie. no d_compare which allows mismatched name
+ * lengths).
+ *
+ * Parent inode i_mutex must be held over d_lookup and into this call (to
+ * keep renames and concurrent inserts, and readdir(2) away).
+ */
+void dentry_update_name_case(struct dentry *dentry, struct qstr *name)
+{
+ BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
+ BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */
+
+ spin_lock(&dcache_lock);
+ spin_lock(&dentry->d_lock);
+ memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
+ spin_unlock(&dentry->d_lock);
+ spin_unlock(&dcache_lock);
+}
+EXPORT_SYMBOL(dentry_update_name_case);
+
/*
* When switching names, the actual string doesn't strictly have to
* be preserved in the target - because we're dropping the target
diff --git a/fs/ncpfs/dir.c b/fs/ncpfs/dir.c
index d6e6453..e80ea4e 100644
--- a/fs/ncpfs/dir.c
+++ b/fs/ncpfs/dir.c
@@ -611,35 +611,12 @@
shrink_dcache_parent(newdent);
/*
- * It is not as dangerous as it looks. NetWare's OS2 namespace is
- * case preserving yet case insensitive. So we update dentry's name
- * as received from server. We found dentry via d_lookup with our
- * hash, so we know that hash does not change, and so replacing name
- * should be reasonably safe.
+ * NetWare's OS2 namespace is case preserving yet case
+ * insensitive. So we update dentry's name as received from
+ * server. Parent dir's i_mutex is locked because we're in
+ * readdir.
*/
- if (qname.len == newdent->d_name.len &&
- memcmp(newdent->d_name.name, qname.name, newdent->d_name.len)) {
- struct inode *inode = newdent->d_inode;
-
- /*
- * Inside ncpfs all uses of d_name are either for debugging,
- * or on functions which acquire inode mutex (mknod, creat,
- * lookup). So grab i_mutex here, to be sure. d_path
- * uses dcache_lock when generating path, so we should too.
- * And finally d_compare is protected by dentry's d_lock, so
- * here we go.
- */
- if (inode)
- mutex_lock(&inode->i_mutex);
- spin_lock(&dcache_lock);
- spin_lock(&newdent->d_lock);
- memcpy((char *) newdent->d_name.name, qname.name,
- newdent->d_name.len);
- spin_unlock(&newdent->d_lock);
- spin_unlock(&dcache_lock);
- if (inode)
- mutex_unlock(&inode->i_mutex);
- }
+ dentry_update_name_case(newdent, &qname);
}
if (!newdent->d_inode) {
@@ -657,7 +634,7 @@
} else {
struct inode *inode = newdent->d_inode;
- mutex_lock(&inode->i_mutex);
+ mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
ncp_update_inode2(inode, entry);
mutex_unlock(&inode->i_mutex);
}
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index cbfc956..6cdf499 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -290,6 +290,8 @@
return res;
}
+extern void dentry_update_name_case(struct dentry *, struct qstr *);
+
/* used for rename() and baskets */
extern void d_move(struct dentry *, struct dentry *);
extern struct dentry *d_ancestor(struct dentry *, struct dentry *);