[PATCH v4 3/3] xfs: reject removal of realtime flag when datadev doesn't support DAX

Dave Jiang
2018-02-15T17:42:44Z

In a situation where the rt_dev is DAX and data_dev is not DAX, if the user
requests to remove the realtime flag via ioctl we can no longer support DAX
for that file. Dynamic changing of S_DAX on the inode is not supported due
to various complications in the existing implementation. Therefore until we
address the dynamic S_DAX change issues, we must disallow realtime flag
being removed.

Signed-off-by: Dave Jiang <dave.jiang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
---
fs/xfs/xfs_ioctl.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)

diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index a6a0efc35c76..a2728f803e26 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -1030,6 +1030,21 @@ xfs_ioctl_setattr_xflags(
{
struct xfs_mount *mp = ip->i_mount;
uint64_t di_flags2;
+ struct inode *inode = VFS_I(ip);
+ struct super_block *sb = inode->i_sb;
+
+ /*
+ * In the case that the inode is realtime, and we are trying to remove
+ * the realtime flag, and the rtdev supports DAX but the datadev does
+ * not support DAX, we can't allow the realtime flag to be removed
+ * since we do not support dynamic S_DAX flag removal yet.
+ */
+ if ((XFS_IS_REALTIME_INODE(ip)) &&
+ !(fa->fsx_xflags & FS_XFLAG_REALTIME) &&
+ bdev_dax_supported(sb, mp->m_rtdev_targp->bt_bdev,
+ sb->s_blocksize) &&
+ !bdev_dax_supported(sb, mp->m_ddev_targp->bt_bdev, sb->s_blocksize))
+ return -ENOTSUPP;

/* Can't change realtime flag if any extents are allocated. */
if ((ip->i_d.di_nextents || ip->i_delayed_blks) &&