9 files changed, 26 insertions, 19 deletions

diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index b8d3ddd8b8db..d392d4b0c393 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -663,3 +663,8 @@ in your dentry operations instead.
         there, but that's it.  Freeing memory in the callback is fine; doing
         more than that is possible, but requires a lot of care and is best
         avoided.
+--
+[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/autofs/autofs_i.h b/fs/autofs/autofs_i.h
index 70c132acdab1..e1091312abe1 100644
--- a/fs/autofs/autofs_i.h
+++ b/fs/autofs/autofs_i.h
@@ -71,6 +71,7 @@ struct autofs_info {
 
         kuid_t uid;
         kgid_t gid;
+        struct rcu_head rcu;
 };
 
 #define AUTOFS_INF_EXPIRING     (1<<0) /* dentry in the process of expiring */
diff --git a/fs/autofs/inode.c b/fs/autofs/inode.c
index 80597b88718b..fb0225f21c12 100644
--- a/fs/autofs/inode.c
+++ b/fs/autofs/inode.c
@@ -36,7 +36,7 @@ void autofs_clean_ino(struct autofs_info *ino)
 
 void autofs_free_ino(struct autofs_info *ino)
 {
-        kfree(ino);
+        kfree_rcu(ino, rcu);
 }
 
 void autofs_kill_sb(struct super_block *sb)
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/internal.h b/fs/internal.h
index 6a8b71643af4..2e7362837a6e 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -89,9 +89,7 @@ extern int sb_prepare_remount_readonly(struct super_block *);
 
 extern void __init mnt_init(void);
 
-extern int __mnt_want_write(struct vfsmount *);
 extern int __mnt_want_write_file(struct file *);
-extern void __mnt_drop_write(struct vfsmount *);
 extern void __mnt_drop_write_file(struct file *);
 
 /*
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;
 
diff --git a/include/linux/mount.h b/include/linux/mount.h
index 9197ddbf35fb..bf8cc4108b8f 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -87,6 +87,8 @@ extern bool mnt_may_suid(struct vfsmount *mnt);
 
 struct path;
 extern struct vfsmount *clone_private_mount(const struct path *path);
+extern int __mnt_want_write(struct vfsmount *);
+extern void __mnt_drop_write(struct vfsmount *);
 
 struct file_system_type;
 extern struct vfsmount *fc_mount(struct fs_context *fc);
diff --git a/kernel/acct.c b/kernel/acct.c
index addf7732fb56..81f9831a7859 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -227,7 +227,7 @@ static int acct_on(struct filename *pathname)
                 filp_close(file, NULL);
                 return PTR_ERR(internal);
         }
-        err = mnt_want_write(internal);
+        err = __mnt_want_write(internal);
         if (err) {
                 mntput(internal);
                 kfree(acct);
@@ -252,7 +252,7 @@ static int acct_on(struct filename *pathname)
         old = xchg(&ns->bacct, &acct->pin);
         mutex_unlock(&acct->lock);
         pin_kill(old);
-        mnt_drop_write(mnt);
+        __mnt_drop_write(mnt);
         mntput(mnt);
         return 0;
 }