Re: [RFC PATCH v3 08/16] ceph: implement -o test_dummy_encryption mount option

Eric Biggers
2020-09-15T01:23:13Z

On Mon, Sep 14, 2020 at 03:16:59PM -0400, Jeff Layton wrote:
> + case Opt_test_dummy_encryption:
> + kfree(fsopt->test_dummy_encryption);
> +#ifdef CONFIG_FS_ENCRYPTION
> + fsopt->test_dummy_encryption = param->string;
> + param->string = NULL;
> + fsopt->flags |= CEPH_MOUNT_OPT_TEST_DUMMY_ENC;
> +#else
> + warnfc(fc, "FS encryption not supported: test_dummy_encryption mount option ignored");
> +#endif

Seems that the kfree() should go in the CONFIG_FS_ENCRYPTION=y block.

Also, is there much reason to have the CEPH_MOUNT_OPT_TEST_DUMMY_ENC flag
instead of just checking fsopt->test_dummy_encryption != NULL?

> +#ifdef CONFIG_FS_ENCRYPTION
> +static int ceph_set_test_dummy_encryption(struct super_block *sb, struct fs_context *fc,
> + struct ceph_mount_options *fsopt)
> +{
> + struct ceph_fs_client *fsc = sb->s_fs_info;
> +
> + if (fsopt->flags & CEPH_MOUNT_OPT_TEST_DUMMY_ENC) {
> + substring_t arg = { };
> +
> + /*
> + * No changing encryption context on remount. Note that
> + * fscrypt_set_test_dummy_encryption will validate the version
> + * string passed in (if any).
> + */
> + if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE && !fsc->dummy_enc_policy.policy)
> + return -EEXIST;

Maybe show an error message here, with errorfc()?
See the message that ext4_set_test_dummy_encryption() shows.

> +
> + /* Ewwwwwwww */
> + if (fsc->mount_options->test_dummy_encryption) {
> + arg.from = fsc->mount_options->test_dummy_encryption;
> + arg.to = arg.from + strlen(arg.from) - 1;
> + }

We should probably make fscrypt_set_test_dummy_encryption() take a
'const char *' to avoid having to create a substring_t here.

> + return fscrypt_set_test_dummy_encryption(sb, &arg, &fsc->dummy_enc_policy);

Likewise, maybe show an error message if this fails.

> + } else {
> + if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE && fsc->dummy_enc_policy.policy)
> + return -EEXIST;

If remount on ceph behaves as "don't change options that aren't specified",
similar to ext4, then there's no need for this hunk here.

> static int ceph_reconfigure_fc(struct fs_context *fc)
> {
> + int err;
> struct ceph_parse_opts_ctx *pctx = fc->fs_private;
> struct ceph_mount_options *fsopt = pctx->opts;
> - struct ceph_fs_client *fsc = ceph_sb_to_client(fc->root->d_sb);
> + struct super_block *sb = fc->root->d_sb;
> + struct ceph_fs_client *fsc = ceph_sb_to_client(sb);
>
> if (fsopt->flags & CEPH_MOUNT_OPT_ASYNC_DIROPS)
> ceph_set_mount_opt(fsc, ASYNC_DIROPS);
> else
> ceph_clear_mount_opt(fsc, ASYNC_DIROPS);
>
> - sync_filesystem(fc->root->d_sb);
> + err = ceph_set_test_dummy_encryption(sb, fc, fsopt);
> + if (err)
> + return err;
> +
> + sync_filesystem(sb);
> return 0;
> }

Seems that ceph_set_test_dummy_encryption() should go at the beginning, since
otherwise it can fail after something was already changed.

- Eric