fs: avoid inode RCU freeing for pseudo fs

Pseudo filesystems that don't put inode on RCU list or reachable by
rcu-walk dentries do not need to RCU free their inodes.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>

2 files changed, 11 insertions, 1 deletions

diff --git a/fs/inode.c b/fs/inode.c
index 6751dfe8cc06..da85e56378f3 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -257,6 +257,12 @@ static struct inode *alloc_inode(struct super_block *sb)
         return inode;
 }
 
+void free_inode_nonrcu(struct inode *inode)
+{
+        kmem_cache_free(inode_cachep, inode);
+}
+EXPORT_SYMBOL(free_inode_nonrcu);
+
 void __destroy_inode(struct inode *inode)
 {
         BUG_ON(inode_has_buffers(inode));
diff --git a/fs/pipe.c b/fs/pipe.c
index 04629f36e397..ae3592dcc88c 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -1253,6 +1253,10 @@ out:
         return ret;
 }
 
+static const struct super_operations pipefs_ops = {
+        .destroy_inode = free_inode_nonrcu,
+};
+
 /*
  * pipefs should _never_ be mounted by userland - too much of security hassle,
  * no real gain from having the whole whorehouse mounted. So we don't need
@@ -1262,7 +1266,7 @@ out:
 static struct dentry *pipefs_mount(struct file_system_type *fs_type,
                          int flags, const char *dev_name, void *data)
 {
-        return mount_pseudo(fs_type, "pipe:", NULL, PIPEFS_MAGIC);
+        return mount_pseudo(fs_type, "pipe:", &pipefs_ops, PIPEFS_MAGIC);
 }
 
 static struct file_system_type pipe_fs_type = {