[PATCH v4 39/46] btrfs: add test_dummy_encryption support

[Josef Bacik <josef@toxicpanda.com>]

In order to enable more thorough testing of fscrypt enable the
test_dummy_encryption mount option.  This is used by fscrypt users to
easily enable fscrypt on the file system for testing without needing to
do the key setup and everything.

The only deviation from other file systems we make is we only support
the fsparam_flag version of this mount option, as it defaults to v2.  We
don't want to have to bother with rejecting v1 related mount options.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/disk-io.c |  1 +
 fs/btrfs/fs.h      |  3 +++
 fs/btrfs/fscrypt.c |  6 +++++
 fs/btrfs/super.c   | 58 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 68 insertions(+)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 719245d73b99..aedd8a0e4962 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1272,6 +1272,7 @@ void btrfs_free_fs_info(struct btrfs_fs_info *fs_info)
 	kfree(fs_info->super_copy);
 	kfree(fs_info->super_for_commit);
 	kfree(fs_info->subpage_info);
+	fscrypt_free_dummy_policy(&fs_info->dummy_enc_policy);
 	kvfree(fs_info);
 }
 
diff --git a/fs/btrfs/fs.h b/fs/btrfs/fs.h
index 1340e71d026c..74752204f3ab 100644
--- a/fs/btrfs/fs.h
+++ b/fs/btrfs/fs.h
@@ -7,6 +7,7 @@
 #include <linux/fs.h>
 #include <linux/btrfs_tree.h>
 #include <linux/sizes.h>
+#include <linux/fscrypt.h>
 #include "extent-io-tree.h"
 #include "extent_map.h"
 #include "async-thread.h"
@@ -189,6 +190,7 @@ enum {
 	BTRFS_MOUNT_IGNOREDATACSUMS		= (1UL << 28),
 	BTRFS_MOUNT_NODISCARD			= (1UL << 29),
 	BTRFS_MOUNT_NOSPACECACHE		= (1UL << 30),
+	BTRFS_MOUNT_TEST_DUMMY_ENCRYPTION	= (1UL << 31),
 };
 
 /*
@@ -828,6 +830,7 @@ struct btrfs_fs_info {
 	spinlock_t eb_leak_lock;
 	struct list_head allocated_ebs;
 #endif
+	struct fscrypt_dummy_policy dummy_enc_policy;
 };
 
 static inline u64 btrfs_get_fs_generation(const struct btrfs_fs_info *fs_info)
diff --git a/fs/btrfs/fscrypt.c b/fs/btrfs/fscrypt.c
index 85b596711371..2fbceec62dc7 100644
--- a/fs/btrfs/fscrypt.c
+++ b/fs/btrfs/fscrypt.c
@@ -242,6 +242,11 @@ static blk_status_t btrfs_process_encrypted_bio(struct bio *orig_bio,
 	return btrfs_csum_one_bio(bbio, enc_bio);
 }
 
+static const union fscrypt_policy *btrfs_get_dummy_policy(struct super_block *sb)
+{
+	return btrfs_sb(sb)->dummy_enc_policy.policy;
+}
+
 int btrfs_fscrypt_load_extent_info(struct btrfs_inode *inode,
 				   struct extent_map *em,
 				   struct btrfs_fscrypt_ctx *ctx)
@@ -357,4 +362,5 @@ const struct fscrypt_operations btrfs_fscrypt_ops = {
 	.empty_dir = btrfs_fscrypt_empty_dir,
 	.get_devices = btrfs_fscrypt_get_devices,
 	.process_bio = btrfs_process_encrypted_bio,
+	.get_dummy_policy = btrfs_get_dummy_policy,
 };
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 462a23db26af..2a7789519a6c 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -88,6 +88,7 @@ struct btrfs_fs_context {
 	unsigned long compress_type:4;
 	unsigned int compress_level;
 	refcount_t refs;
+	struct fscrypt_dummy_policy dummy_enc_policy;
 };
 
 enum {
@@ -122,6 +123,7 @@ enum {
 	Opt_thread_pool,
 	Opt_treelog,
 	Opt_user_subvol_rm_allowed,
+	Opt_test_dummy_encryption,
 
 	/* Rescue options */
 	Opt_rescue,
@@ -255,6 +257,13 @@ static const struct fs_parameter_spec btrfs_fs_parameters[] = {
 	fsparam_flag_no("enospc_debug", Opt_enospc_debug),
 #ifdef CONFIG_BTRFS_DEBUG
 	fsparam_enum("fragment", Opt_fragment, btrfs_parameter_fragment),
+
+	/*
+	 * With -o test_dummy_encryption we default to v2, only allow the flag
+	 * version, since we don't support v1.
+	 */
+	fsparam_flag("test_dummy_encryption", Opt_test_dummy_encryption),
+
 #endif
 #ifdef CONFIG_BTRFS_FS_REF_VERIFY
 	fsparam_flag("ref_verify", Opt_ref_verify),
@@ -268,6 +277,7 @@ static int btrfs_parse_param(struct fs_context *fc,
 	struct btrfs_fs_context *ctx = fc->fs_private;
 	struct fs_parse_result result;
 	int opt;
+	int ret;
 
 	opt = fs_parse(fc, btrfs_fs_parameters, param, &result);
 	if (opt < 0)
@@ -598,6 +608,13 @@ static int btrfs_parse_param(struct fs_context *fc,
 			return -EINVAL;
 		}
 		break;
+	case Opt_test_dummy_encryption:
+		btrfs_set_opt(ctx->mount_opt, TEST_DUMMY_ENCRYPTION);
+		ret = fscrypt_parse_test_dummy_encryption(param,
+							  &ctx->dummy_enc_policy);
+		if (ret)
+			return ret;
+		break;
 #endif
 #ifdef CONFIG_BTRFS_FS_REF_VERIFY
 	case Opt_ref_verify:
@@ -946,6 +963,9 @@ static int btrfs_fill_super(struct super_block *sb,
 		return err;
 	}
 
+	if (fscrypt_is_dummy_policy_set(&fs_info->dummy_enc_policy))
+		btrfs_set_fs_incompat(fs_info, ENCRYPT);
+
 	if (btrfs_fs_incompat(fs_info, ENCRYPT)) {
 		if (IS_ENABLED(CONFIG_FS_ENCRYPTION_INLINE_CRYPT)) {
 			sb->s_flags |= SB_INLINECRYPT;
@@ -1112,6 +1132,9 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 #endif
 	if (btrfs_test_opt(info, REF_VERIFY))
 		seq_puts(seq, ",ref_verify");
+	if (btrfs_test_opt(info, TEST_DUMMY_ENCRYPTION))
+		fscrypt_show_test_dummy_encryption(seq, ',', dentry->d_sb);
+
 	seq_printf(seq, ",subvolid=%llu",
 		  BTRFS_I(d_inode(dentry))->root->root_key.objectid);
 	subvol_name = btrfs_get_subvol_name_from_objectid(info,
@@ -1384,6 +1407,18 @@ static void btrfs_ctx_to_info(struct btrfs_fs_info *fs_info,
 	fs_info->mount_opt = ctx->mount_opt;
 	fs_info->compress_type = ctx->compress_type;
 	fs_info->compress_level = ctx->compress_level;
+
+	/*
+	 * If there's nothing set, or if the fs_info already has one set, don't
+	 * do anything.  If the fs_info is set we'll free the dummy one when we
+	 * free the ctx.
+	 */
+	if (!fscrypt_is_dummy_policy_set(&ctx->dummy_enc_policy) ||
+	    fscrypt_is_dummy_policy_set(&fs_info->dummy_enc_policy))
+		return;
+
+	fs_info->dummy_enc_policy = ctx->dummy_enc_policy;
+	memset(&ctx->dummy_enc_policy, 0, sizeof(ctx->dummy_enc_policy));
 }
 
 static void btrfs_info_to_ctx(struct btrfs_fs_info *fs_info,
@@ -1436,6 +1471,7 @@ static void btrfs_emit_options(struct btrfs_fs_info *info,
 	btrfs_info_if_set(info, old, USEBACKUPROOT, "trying to use backup root at mount time");
 	btrfs_info_if_set(info, old, IGNOREBADROOTS, "ignoring bad roots");
 	btrfs_info_if_set(info, old, IGNOREDATACSUMS, "ignoring data csums");
+	btrfs_info_if_set(info, old, TEST_DUMMY_ENCRYPTION, "test dummy encryption mode enabled");
 
 	btrfs_info_if_unset(info, old, NODATACOW, "setting datacow");
 	btrfs_info_if_unset(info, old, SSD, "not using ssd optimizations");
@@ -1467,6 +1503,23 @@ static void btrfs_emit_options(struct btrfs_fs_info *info,
 			   info->max_inline);
 }
 
+static bool btrfs_check_test_dummy_encryption(struct fs_context *fc)
+{
+	struct btrfs_fs_context *ctx = fc->fs_private;
+	struct btrfs_fs_info *fs_info = btrfs_sb(fc->root->d_sb);
+
+	if (!fscrypt_is_dummy_policy_set(&ctx->dummy_enc_policy))
+		return true;
+
+	if (fscrypt_dummy_policies_equal(&fs_info->dummy_enc_policy,
+					 &ctx->dummy_enc_policy))
+		return true;
+
+	btrfs_warn(fs_info,
+		   "Can't set or change test_dummy_encryption on remount");
+	return false;
+}
+
 static int btrfs_reconfigure(struct fs_context *fc)
 {
 	struct super_block *sb = fc->root->d_sb;
@@ -1485,6 +1538,10 @@ static int btrfs_reconfigure(struct fs_context *fc)
 	    !btrfs_check_options(fs_info, &ctx->mount_opt, fc->sb_flags))
 		return -EINVAL;
 
+	if (!mount_reconfigure &&
+	    !btrfs_check_test_dummy_encryption(fc))
+		return -EINVAL;
+
 	ret = btrfs_check_features(fs_info, !(fc->sb_flags & SB_RDONLY));
 	if (ret < 0)
 		return ret;
@@ -2121,6 +2178,7 @@ static void btrfs_free_fs_context(struct fs_context *fc)
 		btrfs_free_fs_info(fs_info);
 
 	if (ctx && refcount_dec_and_test(&ctx->refs)) {
+		fscrypt_free_dummy_policy(&ctx->dummy_enc_policy);
 		kfree(ctx->subvol_name);
 		kfree(ctx);
 	}
-- 
2.41.0