[PATCH v3 06/27] btrfs: disallow NODATACOW in HMZONED mode

[Naohiro Aota]

NODATACOW implies overwriting the file data on a device, which is
impossible in sequential required zones. Disable NODATACOW globally with
mount option and per-file NODATACOW attribute by masking FS_NOCOW_FL.

Signed-off-by: Naohiro Aota <naohiro.a...@wdc.com>
---
 fs/btrfs/hmzoned.c | 6 ++++++
 fs/btrfs/ioctl.c   | 3 +++
 2 files changed, 9 insertions(+)

diff --git a/fs/btrfs/hmzoned.c b/fs/btrfs/hmzoned.c
index 99a03ab3b5de..0770b1f58bd9 100644
--- a/fs/btrfs/hmzoned.c
+++ b/fs/btrfs/hmzoned.c
@@ -250,5 +250,11 @@ int btrfs_check_mountopts_hmzoned(struct btrfs_fs_info 
*info)
                return -EINVAL;
        }
 
+       if (btrfs_test_opt(info, NODATACOW)) {
+               btrfs_err(info,
+                 "cannot enable nodatacow with HMZONED mode");
+               return -EINVAL;
+       }
+
        return 0;
 }
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index d0743ec1231d..06783c489023 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -93,6 +93,9 @@ static int btrfs_clone(struct inode *src, struct inode *inode,
 static unsigned int btrfs_mask_fsflags_for_type(struct inode *inode,
                unsigned int flags)
 {
+       if (btrfs_fs_incompat(btrfs_sb(inode->i_sb), HMZONED))
+               flags &= ~FS_NOCOW_FL;
+
        if (S_ISDIR(inode->i_mode))
                return flags;
        else if (S_ISREG(inode->i_mode))
-- 
2.22.0