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, 21 insertions, 9 deletions

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 72d357649599..f6b388638c3d 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -168,19 +168,18 @@ static int ecryptfs_initialize_file(struct dentry *ecryptfs_dentry)
                                 "context; rc = [%d]\n", rc);
                 goto out;
         }
-        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;
         }
         rc = ecryptfs_write_metadata(ecryptfs_dentry);
-        if (rc) {
+        if (rc)
                 printk(KERN_ERR "Error writing headers; rc = [%d]\n", rc);
-                goto out;
-        }
+        ecryptfs_put_lower_file(ecryptfs_dentry->d_inode);
 out:
         return rc;
 }
@@ -230,7 +229,7 @@ int ecryptfs_lookup_and_interpose_lower(struct dentry *ecryptfs_dentry,
         struct ecryptfs_crypt_stat *crypt_stat;
         char *page_virt = NULL;
         u64 file_size;
-        int rc = 0;
+        int put_lower = 0, rc = 0;
 
         lower_dir_dentry = lower_dentry->d_parent;
         lower_mnt = mntget(ecryptfs_dentry_to_lower_mnt(
@@ -277,14 +276,15 @@ int ecryptfs_lookup_and_interpose_lower(struct dentry *ecryptfs_dentry,
                 rc = -ENOMEM;
                 goto out;
         }
-        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_kmem;
         }
+        put_lower = 1;
         crypt_stat = &ecryptfs_inode_to_private(
                                         ecryptfs_dentry->d_inode)->crypt_stat;
         /* TODO: lock for crypt_stat comparison */
@@ -322,6 +322,8 @@ out_put:
         mntput(lower_mnt);
         d_drop(ecryptfs_dentry);
 out:
+        if (put_lower)
+                ecryptfs_put_lower_file(ecryptfs_dentry->d_inode);
         return rc;
 }
 
@@ -757,8 +759,11 @@ static int truncate_upper(struct dentry *dentry, struct iattr *ia,
 
         if (unlikely((ia->ia_size == i_size))) {
                 lower_ia->ia_valid &= ~ATTR_SIZE;
-                goto out;
+                return 0;
         }
+        rc = ecryptfs_get_lower_file(dentry);
+        if (rc)
+                return rc;
         crypt_stat = &ecryptfs_inode_to_private(dentry->d_inode)->crypt_stat;
         /* Switch on growing or shrinking file */
         if (ia->ia_size > i_size) {
@@ -836,6 +841,7 @@ static int truncate_upper(struct dentry *dentry, struct iattr *ia,
                         lower_ia->ia_valid &= ~ATTR_SIZE;
         }
 out:
+        ecryptfs_put_lower_file(inode);
         return rc;
 }
 
@@ -911,7 +917,13 @@ static int ecryptfs_setattr(struct dentry *dentry, struct iattr *ia)
 
                 mount_crypt_stat = &ecryptfs_superblock_to_private(
                         dentry->d_sb)->mount_crypt_stat;
+                rc = ecryptfs_get_lower_file(dentry);
+                if (rc) {
+                        mutex_unlock(&crypt_stat->cs_mutex);
+                        goto out;
+                }
                 rc = ecryptfs_read_metadata(dentry);
+                ecryptfs_put_lower_file(inode);
                 if (rc) {
                         if (!(mount_crypt_stat->flags
                               & ECRYPTFS_PLAINTEXT_PASSTHROUGH_ENABLED)) {