From 4a82db7a4b73f1e49ec64c4110879be08f6956d7 Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Wed, 18 Dec 2024 11:17:21 -0800 Subject: [PATCH] xfs: conditionally allow FS_XFLAG_REALTIME changes if S_DAX is set commit 8d16762047c627073955b7ed171a36addaf7b1ff upstream. If a file has the S_DAX flag (aka fsdax access mode) set, we cannot allow users to change the realtime flag unless the datadev and rtdev both support fsdax access modes. Even if there are no extents allocated to the file, the setattr thread could be racing with another thread that has already started down the write code paths. Fixes: ba23cba9b3bdc ("fs: allow per-device dax status checking for filesystems") Signed-off-by: Darrick J. Wong Reviewed-by: Christoph Hellwig Signed-off-by: Chandan Babu R Signed-off-by: Catherine Hoang Acked-by: Darrick J. Wong Signed-off-by: Sasha Levin --- fs/xfs/xfs_ioctl.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c index df4bf0d56aad..32e718043e0e 100644 --- a/fs/xfs/xfs_ioctl.c +++ b/fs/xfs/xfs_ioctl.c @@ -1128,6 +1128,17 @@ xfs_ioctl_setattr_xflags( /* Can't change realtime flag if any extents are allocated. */ if (ip->i_df.if_nextents || ip->i_delayed_blks) return -EINVAL; + + /* + * If S_DAX is enabled on this file, we can only switch the + * device if both support fsdax. We can't update S_DAX because + * there might be other threads walking down the access paths. + */ + if (IS_DAX(VFS_I(ip)) && + (mp->m_ddev_targp->bt_daxdev == NULL || + (mp->m_rtdev_targp && + mp->m_rtdev_targp->bt_daxdev == NULL))) + return -EINVAL; } if (rtflag) {