[PATCH v6 42/43] btrfs: disable encryption on RAID5/6

[Daniel Vacek <neelx@suse.com>]

From: Josef Bacik <josef@toxicpanda.com>

The RAID5/6 code will re-arrange bios and submit them through a
different mechanism.  This is problematic with inline encryption as we
have to get the bio and csum it after it's been encrypted, and the
radi5/6 bio's don't have the btrfs_bio embedded, so we have no way to
get the csums put on disk.

This isn't an unsolvable problem, but would require a bit of reworking.
Since we discourage users from using this code currently simply don't
allow encryption on RAID5/6 setups.  If there's sufficient demand in the
future we can add the support for this.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Daniel Vacek <neelx@suse.com>
---

v5: https://lore.kernel.org/linux-btrfs/941f02bb923edadae1aea4ae3e5aa6ba05d1215a.1706116485.git.josef@toxicpanda.com/
 * No changes since.
---
 fs/btrfs/ioctl.c | 4 ++++
 fs/btrfs/super.c | 6 ++++++
 2 files changed, 10 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index a8adf99ad0a8..1bade8fea16e 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -5198,6 +5198,10 @@ long btrfs_ioctl(struct file *file, unsigned int
 			return -EOPNOTSUPP;
 		if (sb_rdonly(fs_info->sb))
 			return -EROFS;
+		if (btrfs_fs_incompat(fs_info, RAID56)) {
+			btrfs_warn(fs_info, "can't enable encryption with RAID5/6");
+			return -EINVAL;
+		}
 		/*
 		 *  If we crash before we commit, nothing encrypted could have
 		 * been written so it doesn't matter whether the encrypted
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 4a2887147ead..aefcbe56e85a 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -734,6 +734,12 @@ bool btrfs_check_options(const struct btrfs_fs_info *info,
 	if (btrfs_check_mountopts_zoned(info, mount_opt))
 		ret = false;
 
+	if (btrfs_fs_incompat(info, RAID56) &&
+	    btrfs_raw_test_opt(*mount_opt, TEST_DUMMY_ENCRYPTION)) {
+		btrfs_err(info, "cannot use test_dummy_encryption with RAID5/6");
+		ret = false;
+	}
+
 	if (!test_bit(BTRFS_FS_STATE_REMOUNTING, &info->fs_state)) {
 		if (btrfs_raw_test_opt(*mount_opt, SPACE_CACHE)) {
 			btrfs_warn(info,
-- 
2.51.0