eCryptfs: Cleanup and optimize ecryptfs_lookup_interpose()

ecryptfs_lookup_interpose() has turned into spaghetti code over the
years. This is an effort to clean it up.

 - Shorten overly descriptive variable names such as ecryptfs_dentry
 - Simplify gotos and error paths
 - Create helper function for reading plaintext i_size from metadata

It also includes an optimization when reading i_size from the metadata.
A complete page-sized kmem_cache_alloc() was being done to read in 16
bytes of metadata. The buffer for that is now statically declared.

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

1 files changed, 63 insertions, 78 deletions

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index f0ad965d7d5..7349ade17de 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -307,105 +307,90 @@ out:
 	return rc;
 }
 
+static int ecryptfs_i_size_read(struct dentry *dentry, struct inode *inode)
+{
+	struct ecryptfs_crypt_stat *crypt_stat;
+	int rc;
+
+	rc = ecryptfs_get_lower_file(dentry, inode);
+	if (rc) {
+		printk(KERN_ERR "%s: Error attempting to initialize "
+			"the lower file for the dentry with name "
+			"[%s]; rc = [%d]\n", __func__,
+			dentry->d_name.name, rc);
+		return rc;
+	}
+
+	crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
+	/* TODO: lock for crypt_stat comparison */
+	if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED))
+		ecryptfs_set_default_sizes(crypt_stat);
+
+	rc = ecryptfs_read_and_validate_header_region(inode);
+	ecryptfs_put_lower_file(inode);
+	if (rc) {
+		rc = ecryptfs_read_and_validate_xattr_region(dentry, inode);
+		if (!rc)
+			crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
+	}
+
+	/* Must return 0 to allow non-eCryptfs files to be looked up, too */
+	return 0;
+}
+
 /**
  * ecryptfs_lookup_interpose - Dentry interposition for a lookup
  */
-static int ecryptfs_lookup_interpose(struct dentry *ecryptfs_dentry,
+static int ecryptfs_lookup_interpose(struct dentry *dentry,
 				     struct dentry *lower_dentry,
-				     struct inode *ecryptfs_dir_inode)
+				     struct inode *dir_inode)
 {
-	struct dentry *lower_dir_dentry;
+	struct inode *inode, *lower_inode = lower_dentry->d_inode;
+	struct ecryptfs_dentry_info *dentry_info;
 	struct vfsmount *lower_mnt;
-	struct inode *inode, *lower_inode;
-	struct ecryptfs_crypt_stat *crypt_stat;
-	char *page_virt = NULL;
-	int put_lower = 0, rc = 0;
-
-	lower_dir_dentry = lower_dentry->d_parent;
-	lower_mnt = mntget(ecryptfs_dentry_to_lower_mnt(
-				   ecryptfs_dentry->d_parent));
-	lower_inode = lower_dentry->d_inode;
-	fsstack_copy_attr_atime(ecryptfs_dir_inode, lower_dir_dentry->d_inode);
+	int rc = 0;
+
+	lower_mnt = mntget(ecryptfs_dentry_to_lower_mnt(dentry->d_parent));
+	fsstack_copy_attr_atime(dir_inode, lower_dentry->d_parent->d_inode);
 	BUG_ON(!lower_dentry->d_count);
-	ecryptfs_set_dentry_private(ecryptfs_dentry,
-				    kmem_cache_alloc(ecryptfs_dentry_info_cache,
-						     GFP_KERNEL));
-	if (!ecryptfs_dentry_to_private(ecryptfs_dentry)) {
-		rc = -ENOMEM;
+
+	dentry_info = kmem_cache_alloc(ecryptfs_dentry_info_cache, GFP_KERNEL);
+	ecryptfs_set_dentry_private(dentry, dentry_info);
+	if (!dentry_info) {
 		printk(KERN_ERR "%s: Out of memory whilst attempting "
 		       "to allocate ecryptfs_dentry_info struct\n",
 			__func__);
-		goto out_put;
+		dput(lower_dentry);
+		mntput(lower_mnt);
+		d_drop(dentry);
+		return -ENOMEM;
 	}
-	ecryptfs_set_dentry_lower(ecryptfs_dentry, lower_dentry);
-	ecryptfs_set_dentry_lower_mnt(ecryptfs_dentry, lower_mnt);
+	ecryptfs_set_dentry_lower(dentry, lower_dentry);
+	ecryptfs_set_dentry_lower_mnt(dentry, lower_mnt);
+
 	if (!lower_dentry->d_inode) {
 		/* We want to add because we couldn't find in lower */
-		d_add(ecryptfs_dentry, NULL);
-		goto out;
+		d_add(dentry, NULL);
+		return 0;
 	}
-	inode = __ecryptfs_get_inode(lower_inode, ecryptfs_dir_inode->i_sb);
+	inode = __ecryptfs_get_inode(lower_inode, dir_inode->i_sb);
 	if (IS_ERR(inode)) {
-		rc = PTR_ERR(inode);
-		printk(KERN_ERR "%s: Error interposing; rc = [%d]\n",
-		       __func__, rc);
-		goto out;
-	}
-	if (!S_ISREG(inode->i_mode)) {
-		if (inode->i_state & I_NEW)
-			unlock_new_inode(inode);
-		d_add(ecryptfs_dentry, inode);
-		goto out;
-	}
-	/* Released in this function */
-	page_virt = kmem_cache_zalloc(ecryptfs_header_cache_2, GFP_USER);
-	if (!page_virt) {
-		printk(KERN_ERR "%s: Cannot kmem_cache_zalloc() a page\n",
-		       __func__);
-		rc = -ENOMEM;
-		make_bad_inode(inode);
-		goto out;
-	}
-	rc = ecryptfs_get_lower_file(ecryptfs_dentry, inode);
-	if (rc) {
-		printk(KERN_ERR "%s: Error attempting to initialize "
-			"the lower file for the dentry with name "
-			"[%s]; rc = [%d]\n", __func__,
-			ecryptfs_dentry->d_name.name, rc);
-		make_bad_inode(inode);
-		goto out_free_kmem;
+		printk(KERN_ERR "%s: Error interposing; rc = [%ld]\n",
+		       __func__, PTR_ERR(inode));
+		return PTR_ERR(inode);
 	}
-	put_lower = 1;
-	crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
-	/* TODO: lock for crypt_stat comparison */
-	if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED))
-			ecryptfs_set_default_sizes(crypt_stat);
-	rc = ecryptfs_read_and_validate_header_region(page_virt, inode);
-	if (rc) {
-		memset(page_virt, 0, PAGE_CACHE_SIZE);
-		rc = ecryptfs_read_and_validate_xattr_region(page_virt,
-							     inode);
+	if (S_ISREG(inode->i_mode)) {
+		rc = ecryptfs_i_size_read(dentry, inode);
 		if (rc) {
-			rc = 0;
-			goto unlock_inode;
+			make_bad_inode(inode);
+			return rc;
 		}
-		crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
 	}
-	ecryptfs_i_size_init(page_virt, inode);
-unlock_inode:
+
 	if (inode->i_state & I_NEW)
 		unlock_new_inode(inode);
-	d_add(ecryptfs_dentry, inode);
-out_free_kmem:
-	kmem_cache_free(ecryptfs_header_cache_2, page_virt);
-	goto out;
-out_put:
-	dput(lower_dentry);
-	mntput(lower_mnt);
-	d_drop(ecryptfs_dentry);
-out:
-	if (put_lower)
-		ecryptfs_put_lower_file(inode);
+	d_add(dentry, inode);
+
 	return rc;
 }