1 files changed, 56 insertions, 0 deletions

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index edb30621b82f..c6f3b697064c 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -435,6 +435,62 @@ void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
 }
 
 /**
+ *      sysfs_drop_dentry - drop dentry for the specified sysfs_dirent
+ *      @sd: target sysfs_dirent
+ *
+ *      Drop dentry for @sd.  @sd must have been unlinked from its
+ *      parent on entry to this function such that it can't be looked
+ *      up anymore.
+ *
+ *      @sd->s_dentry which is protected with sysfs_assoc_lock points
+ *      to the currently associated dentry but we're not holding a
+ *      reference to it and racing with dput().  Grab dcache_lock and
+ *      verify dentry before dropping it.  If @sd->s_dentry is NULL or
+ *      dput() beats us, no need to bother.
+ */
+static void sysfs_drop_dentry(struct sysfs_dirent *sd)
+{
+        struct dentry *dentry = NULL;
+        struct inode *inode;
+
+        /* We're not holding a reference to ->s_dentry dentry but the
+         * field will stay valid as long as sysfs_assoc_lock is held.
+         */
+        spin_lock(&sysfs_assoc_lock);
+        spin_lock(&dcache_lock);
+
+        /* drop dentry if it's there and dput() didn't kill it yet */
+        if (sd->s_dentry && sd->s_dentry->d_inode) {
+                dentry = dget_locked(sd->s_dentry);
+                spin_lock(&dentry->d_lock);
+                __d_drop(dentry);
+                spin_unlock(&dentry->d_lock);
+        }
+
+        spin_unlock(&dcache_lock);
+        spin_unlock(&sysfs_assoc_lock);
+
+        dput(dentry);
+        /* XXX: unpin if directory, this will go away soon */
+        if (sysfs_type(sd) == SYSFS_DIR)
+                dput(dentry);
+
+        /* adjust nlink and update timestamp */
+        inode = ilookup(sysfs_sb, sd->s_ino);
+        if (inode) {
+                mutex_lock(&inode->i_mutex);
+
+                inode->i_ctime = CURRENT_TIME;
+                drop_nlink(inode);
+                if (sysfs_type(sd) == SYSFS_DIR)
+                        drop_nlink(inode);
+
+                mutex_unlock(&inode->i_mutex);
+                iput(inode);
+        }
+}
+
+/**
  *      sysfs_addrm_finish - finish up sysfs_dirent add/remove
  *      @acxt: addrm context to finish up
  *