Re: [PATCH 1/2] ceph: don't clobber i_snap_caps on non-I_NEW inode

[Xiubo Li <xiubli@redhat.com>]

On 2021/3/16 2:07, Jeff Layton wrote:
> We want the snapdir to mirror the non-snapped directory's attributes for
> most things, but i_snap_caps represents the caps granted on the snapshot
> directory by the MDS itself. A misbehaving MDS could issue different
> caps for the snapdir and we lose them here.
>
> Only reset i_snap_caps when the inode is I_NEW.
>
> Reported-by: Al Viro <viro@zeniv.linux.org.uk>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
>   fs/ceph/inode.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
> index 26dc7a296f6b..fc7f4bf63306 100644
> --- a/fs/ceph/inode.c
> +++ b/fs/ceph/inode.c
> @@ -101,12 +101,13 @@ struct inode *ceph_get_snapdir(struct inode *parent)
>   	inode->i_atime = parent->i_atime;
>   	inode->i_op = &ceph_snapdir_iops;
>   	inode->i_fop = &ceph_snapdir_fops;
> -	ci->i_snap_caps = CEPH_CAP_PIN; /* so we can open */
> -	ci->i_rbytes = 0;
>   	ci->i_btime = ceph_inode(parent)->i_btime;
> +	ci->i_rbytes = 0;
>   

Hi Jeff,

BTW, why we need to set other members here if the i_state is not I_NEW ?

Are they necessary ?

> -	if (inode->i_state & I_NEW)
> +	if (inode->i_state & I_NEW) {
> +		ci->i_snap_caps = CEPH_CAP_PIN; /* so we can open */
>   		unlock_new_inode(inode);
> +	}
>   
>   	return inode;
>   }