4 files changed, 20 insertions, 14 deletions

diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index cf43bc4dbf31..a60fa516d4cb 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -638,3 +638,8 @@ in your dentry operations instead.
         inode to d_splice_alias() will also do the right thing (equivalent of
         d_add(dentry, NULL); return NULL;), so that kind of special cases
         also doesn't need a separate treatment.
+--
+[mandatory]
+        DCACHE_RCUACCESS is gone; having an RCU delay on dentry freeing is the
+        default.  DCACHE_NORCU opts out, and only d_alloc_pseudo() has any
+        business doing so.
diff --git a/fs/dcache.c b/fs/dcache.c
index aac41adf4743..c663c602f9ef 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -344,7 +344,7 @@ static void dentry_free(struct dentry *dentry)
                 }
         }
         /* if dentry was never visible to RCU, immediate free is OK */
-        if (!(dentry->d_flags & DCACHE_RCUACCESS))
+        if (dentry->d_flags & DCACHE_NORCU)
                 __d_free(&dentry->d_u.d_rcu);
         else
                 call_rcu(&dentry->d_u.d_rcu, __d_free);
@@ -1701,7 +1701,6 @@ struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
         struct dentry *dentry = __d_alloc(parent->d_sb, name);
         if (!dentry)
                 return NULL;
-        dentry->d_flags |= DCACHE_RCUACCESS;
         spin_lock(&parent->d_lock);
         /*
          * don't need child lock because it is not subject
@@ -1726,7 +1725,7 @@ struct dentry *d_alloc_cursor(struct dentry * parent)
 {
         struct dentry *dentry = d_alloc_anon(parent->d_sb);
         if (dentry) {
-                dentry->d_flags |= DCACHE_RCUACCESS | DCACHE_DENTRY_CURSOR;
+                dentry->d_flags |= DCACHE_DENTRY_CURSOR;
                 dentry->d_parent = dget(parent);
         }
         return dentry;
@@ -1739,10 +1738,17 @@ struct dentry *d_alloc_cursor(struct dentry * parent)
  *
  * For a filesystem that just pins its dentries in memory and never
  * performs lookups at all, return an unhashed IS_ROOT dentry.
+ * This is used for pipes, sockets et.al. - the stuff that should
+ * never be anyone's children or parents.  Unlike all other
+ * dentries, these will not have RCU delay between dropping the
+ * last reference and freeing them.
  */
 struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
 {
-        return __d_alloc(sb, name);
+        struct dentry *dentry = __d_alloc(sb, name);
+        if (likely(dentry))
+                dentry->d_flags |= DCACHE_NORCU;
+        return dentry;
 }
 EXPORT_SYMBOL(d_alloc_pseudo);
 
@@ -1911,12 +1917,10 @@ struct dentry *d_make_root(struct inode *root_inode)
 
         if (root_inode) {
                 res = d_alloc_anon(root_inode->i_sb);
-                if (res) {
-                        res->d_flags |= DCACHE_RCUACCESS;
+                if (res)
                         d_instantiate(res, root_inode);
-                } else {
+                else
                         iput(root_inode);
-                }
         }
         return res;
 }
@@ -2781,9 +2785,7 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
                 copy_name(dentry, target);
                 target->d_hash.pprev = NULL;
                 dentry->d_parent->d_lockref.count++;
-                if (dentry == old_parent)
-                        dentry->d_flags |= DCACHE_RCUACCESS;
-                else
+                if (dentry != old_parent) /* wasn't IS_ROOT */
                         WARN_ON(!--old_parent->d_lockref.count);
         } else {
                 target->d_parent = old_parent;
diff --git a/fs/nsfs.c b/fs/nsfs.c
index 60702d677bd4..30d150a4f0c6 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -85,13 +85,12 @@ slow:
         inode->i_fop = &ns_file_operations;
         inode->i_private = ns;
 
-        dentry = d_alloc_pseudo(mnt->mnt_sb, &empty_name);
+        dentry = d_alloc_anon(mnt->mnt_sb);
         if (!dentry) {
                 iput(inode);
                 return ERR_PTR(-ENOMEM);
         }
         d_instantiate(dentry, inode);
-        dentry->d_flags |= DCACHE_RCUACCESS;
         dentry->d_fsdata = (void *)ns->ops;
         d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry);
         if (d) {
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 60996e64c579..6e1e8e6602c6 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -176,7 +176,6 @@ struct dentry_operations {
       * typically using d_splice_alias. */
 
 #define DCACHE_REFERENCED               0x00000040 /* Recently used, don't discard. */
-#define DCACHE_RCUACCESS                0x00000080 /* Entry has ever been RCU-visible */
 
 #define DCACHE_CANT_MOUNT               0x00000100
 #define DCACHE_GENOCIDE                 0x00000200
@@ -217,6 +216,7 @@ struct dentry_operations {
 
 #define DCACHE_PAR_LOOKUP               0x10000000 /* being looked up (with parent locked shared) */
 #define DCACHE_DENTRY_CURSOR            0x20000000
+#define DCACHE_NORCU                    0x40000000 /* No RCU delay for freeing */
 
 extern seqlock_t rename_lock;