Re: [PATCH v4 3/4] NFSD: handle GETATTR conflict with write delegation

[Jeff Layton <jlayton@kernel.org>]

On Sat, 2023-05-20 at 14:36 -0700, Dai Ngo wrote:
> If the GETATTR request on a file that has write delegation in effect
> and the request attributes include the change info and size attribute
> then the write delegation is recalled and NFS4ERR_DELAY is returned
> for the GETATTR.
> 
> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
> ---
>  fs/nfsd/nfs4xdr.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 45 insertions(+)
> 
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 76db2fe29624..e069b970f136 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -2920,6 +2920,46 @@ nfsd4_encode_bitmap(struct xdr_stream *xdr, u32 bmval0, u32 bmval1, u32 bmval2)
>  	return nfserr_resource;
>  }
>  
> +static struct file_lock *
> +nfs4_wrdeleg_filelock(struct svc_rqst *rqstp, struct inode *inode)
> +{
> +	struct file_lock_context *ctx;
> +	struct file_lock *fl;
> +
> +	ctx = locks_inode_context(inode);
> +	if (!ctx)
> +		return NULL;
> +	spin_lock(&ctx->flc_lock);
> +	if (!list_empty(&ctx->flc_lease)) {
> +		fl = list_first_entry(&ctx->flc_lease,
> +					struct file_lock, fl_list);
> +		if (fl->fl_type == F_WRLCK) {
> +			spin_unlock(&ctx->flc_lock);
> +			return fl;
> +		}
> +	}
> +	spin_unlock(&ctx->flc_lock);
> +	return NULL;
> +}
> +
> +static __be32
> +nfs4_handle_wrdeleg_conflict(struct svc_rqst *rqstp, struct inode *inode)
> +{
> +	__be32 status;
> +	struct file_lock *fl;
> +	struct nfs4_delegation *dp;
> +
> +	fl = nfs4_wrdeleg_filelock(rqstp, inode);
> +	if (!fl)
> +		return 0;
> +	dp = fl->fl_owner;
> +	if (dp->dl_recall.cb_clp == *(rqstp->rq_lease_breaker))
> +		return 0;
> +	refcount_inc(&dp->dl_stid.sc_count);

Another question: Why are you taking a reference here at all? AFAICT,
you don't even look at the delegation again after that point, so it's
not clear to me who's responsible for putting that reference.

> +	status = nfserrno(nfsd_open_break_lease(inode, NFSD_MAY_READ));
> +	return status;
> +}
> +
>  /*
>   * Note: @fhp can be NULL; in this case, we might have to compose the filehandle
>   * ourselves.
> @@ -2966,6 +3006,11 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
>  		if (status)
>  			goto out;
>  	}
> +	if (bmval0 & (FATTR4_WORD0_CHANGE | FATTR4_WORD0_SIZE)) {
> +		status = nfs4_handle_wrdeleg_conflict(rqstp, d_inode(dentry));
> +		if (status)
> +			goto out;
> +	}
>  
>  	err = vfs_getattr(&path, &stat,
>  			  STATX_BASIC_STATS | STATX_BTIME | STATX_CHANGE_COOKIE,

-- 
Jeff Layton <jlayton@kernel.org>