1 files changed, 31 insertions, 0 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 268da2e2bc09..2135ab8bb103 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1853,6 +1853,16 @@ char * d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
         struct vfsmount *rootmnt;
         struct dentry *root;
 
+        /*
+         * We have various synthetic filesystems that never get mounted.  On
+         * these filesystems dentries are never used for lookup purposes, and
+         * thus don't need to be hashed.  They also don't need a name until a
+         * user wants to identify the object in /proc/pid/fd/.  The little hack
+         * below allows us to generate a name for these objects on demand:
+         */
+        if (dentry->d_op && dentry->d_op->d_dname)
+                return dentry->d_op->d_dname(dentry, buf, buflen);
+
         read_lock(&current->fs->lock);
         rootmnt = mntget(current->fs->rootmnt);
         root = dget(current->fs->root);
@@ -1866,6 +1876,27 @@ char * d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
 }
 
 /*
+ * Helper function for dentry_operations.d_dname() members
+ */
+char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
+                        const char *fmt, ...)
+{
+        va_list args;
+        char temp[64];
+        int sz;
+
+        va_start(args, fmt);
+        sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
+        va_end(args);
+
+        if (sz > sizeof(temp) || sz > buflen)
+                return ERR_PTR(-ENAMETOOLONG);
+
+        buffer += buflen - sz;
+        return memcpy(buffer, temp, sz);
+}
+
+/*
  * NOTE! The user-level library version returns a
  * character pointer. The kernel system call just
  * returns the length of the buffer filled (which