eCryptfs: Add reference counting to lower files

For any given lower inode, eCryptfs keeps only one lower file open and
multiplexes all eCryptfs file operations through that lower file. The
lower file was considered "persistent" and stayed open from the first
lookup through the lifetime of the inode.

This patch keeps the notion of a single, per-inode lower file, but adds
reference counting around the lower file so that it is closed when not
currently in use. If the reference count is at 0 when an operation (such
as open, create, etc.) needs to use the lower file, a new lower file is
opened. Since the file is no longer persistent, all references to the
term persistent file are changed to lower file.

Locking is added around the sections of code that opens the lower file
and assign the pointer in the inode info, as well as the code the fputs
the lower file when all eCryptfs users are done with it.

This patch is needed to fix issues, when mounted on top of the NFSv3
client, where the lower file is left silly renamed until the eCryptfs
inode is destroyed.

Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/fs/ecryptfs/kthread.c b/fs/ecryptfs/kthread.c
index 0851ab6..69f994a 100644
--- a/fs/ecryptfs/kthread.c
+++ b/fs/ecryptfs/kthread.c
@@ -44,7 +44,7 @@ static struct task_struct *ecryptfs_kthread;
  * @ignored: ignored
  *
  * The eCryptfs kernel thread that has the responsibility of getting
- * the lower persistent file with RW permissions.
+ * the lower file with RW permissions.
  *
  * Returns zero on success; non-zero otherwise
  */
@@ -141,8 +141,8 @@ int ecryptfs_privileged_open(struct file **lower_file,
 	int rc = 0;
 
 	/* Corresponding dput() and mntput() are done when the
-	 * persistent file is fput() when the eCryptfs inode is
-	 * destroyed. */
+	 * lower file is fput() when all eCryptfs files for the inode are
+	 * released. */
 	dget(lower_dentry);
 	mntget(lower_mnt);
 	flags |= IS_RDONLY(lower_dentry->d_inode) ? O_RDONLY : O_RDWR;