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, 10 insertions, 12 deletions

diff --git a/fs/ecryptfs/file.c b/fs/ecryptfs/file.c
index cedc913d11b..146c4edff70 100644
--- a/fs/ecryptfs/file.c
+++ b/fs/ecryptfs/file.c
@@ -191,10 +191,10 @@ static int ecryptfs_open(struct inode *inode, struct file *file)
 				      | ECRYPTFS_ENCRYPTED);
 	}
 	mutex_unlock(&crypt_stat->cs_mutex);
-	rc = ecryptfs_init_persistent_file(ecryptfs_dentry);
+	rc = ecryptfs_get_lower_file(ecryptfs_dentry);
 	if (rc) {
 		printk(KERN_ERR "%s: Error attempting to initialize "
-			"the persistent file for the dentry with name "
+			"the lower file for the dentry with name "
 			"[%s]; rc = [%d]\n", __func__,
 			ecryptfs_dentry->d_name.name, rc);
 		goto out_free;
@@ -202,9 +202,9 @@ static int ecryptfs_open(struct inode *inode, struct file *file)
 	if ((ecryptfs_inode_to_private(inode)->lower_file->f_flags & O_ACCMODE)
 	    == O_RDONLY && (file->f_flags & O_ACCMODE) != O_RDONLY) {
 		rc = -EPERM;
-		printk(KERN_WARNING "%s: Lower persistent file is RO; eCryptfs "
+		printk(KERN_WARNING "%s: Lower file is RO; eCryptfs "
 		       "file must hence be opened RO\n", __func__);
-		goto out_free;
+		goto out_put;
 	}
 	ecryptfs_set_file_lower(
 		file, ecryptfs_inode_to_private(inode)->lower_file);
@@ -232,7 +232,7 @@ static int ecryptfs_open(struct inode *inode, struct file *file)
 				       "Plaintext passthrough mode is not "
 				       "enabled; returning -EIO\n");
 				mutex_unlock(&crypt_stat->cs_mutex);
-				goto out_free;
+				goto out_put;
 			}
 			rc = 0;
 			crypt_stat->flags &= ~(ECRYPTFS_ENCRYPTED);
@@ -245,6 +245,8 @@ static int ecryptfs_open(struct inode *inode, struct file *file)
 			"[0x%.16lx] size: [0x%.16llx]\n", inode, inode->i_ino,
 			(unsigned long long)i_size_read(inode));
 	goto out;
+out_put:
+	ecryptfs_put_lower_file(inode);
 out_free:
 	kmem_cache_free(ecryptfs_file_info_cache,
 			ecryptfs_file_to_private(file));
@@ -254,17 +256,13 @@ out:
 
 static int ecryptfs_flush(struct file *file, fl_owner_t td)
 {
-	int rc = 0;
-	struct file *lower_file = NULL;
-
-	lower_file = ecryptfs_file_to_lower(file);
-	if (lower_file->f_op && lower_file->f_op->flush)
-		rc = lower_file->f_op->flush(lower_file, td);
-	return rc;
+	return file->f_mode & FMODE_WRITE
+	       ? filemap_write_and_wait(file->f_mapping) : 0;
 }
 
 static int ecryptfs_release(struct inode *inode, struct file *file)
 {
+	ecryptfs_put_lower_file(inode);
 	kmem_cache_free(ecryptfs_file_info_cache,
 			ecryptfs_file_to_private(file));
 	return 0;