ecryptfs: modify write path to encrypt page in writepage

Change the write path to encrypt the data only when the page is written to
disk in ecryptfs_writepage. Previously, ecryptfs encrypts the page in
ecryptfs_write_end which means that if there are multiple write requests to
the same page, ecryptfs ends up re-encrypting that page over and over again.
This patch minimizes the number of encryptions needed.

Signed-off-by: Thieu Le <[email protected]>
[tyhicks: Changed NULL .drop_inode sop pointer to generic_drop_inode]
Signed-off-by: Tyler Hicks <[email protected]>

Author: Thieu Le

fs/ecryptfs/ecryptfs_kernel.h

@@ -296,7 +296,6 @@ struct ecryptfs_inode_info {
 	struct inode vfs_inode;
 	struct inode *wii_inode;
 	struct file *lower_file;
-	struct mutex lower_file_mutex;
 	struct ecryptfs_crypt_stat crypt_stat;
 };
 

fs/ecryptfs/file.c

@@ -273,7 +273,14 @@ static int ecryptfs_release(struct inode *inode, struct file *file)
 static int
 ecryptfs_fsync(struct file *file, int datasync)
 {
-	return vfs_fsync(ecryptfs_file_to_lower(file), datasync);
+	int rc = 0;
+
+	rc = generic_file_fsync(file, datasync);
+	if (rc)
+		goto out;
+	rc = vfs_fsync(ecryptfs_file_to_lower(file), datasync);
+out:
+	return rc;
 }
 
 static int ecryptfs_fasync(int fd, struct file *file, int flag)

fs/ecryptfs/main.c

@@ -122,7 +122,6 @@ int ecryptfs_init_persistent_file(struct dentry *ecryptfs_dentry)
 		ecryptfs_inode_to_private(ecryptfs_dentry->d_inode);
 	int rc = 0;
 
-	mutex_lock(&inode_info->lower_file_mutex);
 	if (!inode_info->lower_file) {
 		struct dentry *lower_dentry;
 		struct vfsmount *lower_mnt =
@@ -138,7 +137,6 @@ int ecryptfs_init_persistent_file(struct dentry *ecryptfs_dentry)
 			inode_info->lower_file = NULL;
 		}
 	}
-	mutex_unlock(&inode_info->lower_file_mutex);
 	return rc;
 }
 

fs/ecryptfs/mmap.c

@@ -62,6 +62,18 @@ static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
 {
 	int rc;
 
+	/*
+	 * Refuse to write the page out if we are called from reclaim context
+	 * since our writepage() path may potentially allocate memory when
+	 * calling into the lower fs vfs_write() which may in turn invoke
+	 * us again.
+	 */
+	if (current->flags & PF_MEMALLOC) {
+		redirty_page_for_writepage(wbc, page);
+		rc = 0;
+		goto out;
+	}
+
 	rc = ecryptfs_encrypt_page(page);
 	if (rc) {
 		ecryptfs_printk(KERN_WARNING, "Error encrypting "
@@ -70,8 +82,8 @@ static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
 		goto out;
 	}
 	SetPageUptodate(page);
-	unlock_page(page);
 out:
+	unlock_page(page);
 	return rc;
 }
 
@@ -481,6 +493,7 @@ static int ecryptfs_write_end(struct file *file,
 	struct ecryptfs_crypt_stat *crypt_stat =
 		&ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 	int rc;
+	int need_unlock_page = 1;
 
 	ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
 			"(page w/ index = [0x%.16lx], to = [%d])\n", index, to);
@@ -501,26 +514,26 @@ static int ecryptfs_write_end(struct file *file,
 			"zeros in page with index = [0x%.16lx]\n", index);
 		goto out;
 	}
-	rc = ecryptfs_encrypt_page(page);
-	if (rc) {
-		ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
-				"index [0x%.16lx])\n", index);
-		goto out;
-	}
+	set_page_dirty(page);
+	unlock_page(page);
+	need_unlock_page = 0;
 	if (pos + copied > i_size_read(ecryptfs_inode)) {
 		i_size_write(ecryptfs_inode, pos + copied);
 		ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
 			"[0x%.16llx]\n",
 			(unsigned long long)i_size_read(ecryptfs_inode));
+		balance_dirty_pages_ratelimited(mapping);
+		rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
+		if (rc) {
+			printk(KERN_ERR "Error writing inode size to metadata; "
+			       "rc = [%d]\n", rc);
+			goto out;
+		}
 	}
-	rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
-	if (rc)
-		printk(KERN_ERR "Error writing inode size to metadata; "
-		       "rc = [%d]\n", rc);
-	else
-		rc = copied;
+	rc = copied;
 out:
-	unlock_page(page);
+	if (need_unlock_page)
+		unlock_page(page);
 	page_cache_release(page);
 	return rc;
 }

fs/ecryptfs/read_write.c

@@ -44,15 +44,11 @@ int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data,
 	ssize_t rc;
 
 	inode_info = ecryptfs_inode_to_private(ecryptfs_inode);
-	mutex_lock(&inode_info->lower_file_mutex);
 	BUG_ON(!inode_info->lower_file);
-	inode_info->lower_file->f_pos = offset;
 	fs_save = get_fs();
 	set_fs(get_ds());
-	rc = vfs_write(inode_info->lower_file, data, size,
-		       &inode_info->lower_file->f_pos);
+	rc = vfs_write(inode_info->lower_file, data, size, &offset);
 	set_fs(fs_save);
-	mutex_unlock(&inode_info->lower_file_mutex);
 	mark_inode_dirty_sync(ecryptfs_inode);
 	return rc;
 }
@@ -234,15 +230,11 @@ int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
 	mm_segment_t fs_save;
 	ssize_t rc;
 
-	mutex_lock(&inode_info->lower_file_mutex);
 	BUG_ON(!inode_info->lower_file);
-	inode_info->lower_file->f_pos = offset;
 	fs_save = get_fs();
 	set_fs(get_ds());
-	rc = vfs_read(inode_info->lower_file, data, size,
-		      &inode_info->lower_file->f_pos);
+	rc = vfs_read(inode_info->lower_file, data, size, &offset);
 	set_fs(fs_save);
-	mutex_unlock(&inode_info->lower_file_mutex);
 	return rc;
 }
 

fs/ecryptfs/super.c

@@ -55,7 +55,6 @@ static struct inode *ecryptfs_alloc_inode(struct super_block *sb)
 	if (unlikely(!inode_info))
 		goto out;
 	ecryptfs_init_crypt_stat(&inode_info->crypt_stat);
-	mutex_init(&inode_info->lower_file_mutex);
 	inode_info->lower_file = NULL;
 	inode = &inode_info->vfs_inode;
 out:
@@ -198,7 +197,7 @@ static int ecryptfs_show_options(struct seq_file *m, struct vfsmount *mnt)
 const struct super_operations ecryptfs_sops = {
 	.alloc_inode = ecryptfs_alloc_inode,
 	.destroy_inode = ecryptfs_destroy_inode,
-	.drop_inode = generic_delete_inode,
+	.drop_inode = generic_drop_inode,
 	.statfs = ecryptfs_statfs,
 	.remount_fs = NULL,
 	.evict_inode = ecryptfs_evict_inode,