Re: [PATCH v2 4/4] NFSD: handle GETATTR conflict with write delegation

[Jeff Layton <jlayton@kernel.org>]

On Sun, 2023-05-14 at 17:20 -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 request is handled as below:
> 
> Server sends CB_GETATTR to client to get the latest change info and file
> size. If these values are the same as the server's cached values then
> the GETATTR proceeds as normal.
> 
> If either the change info or file size is different from the server's
> cached values, or the file was already marked as modified, then:
> 
>    . update time_modify and time_metadata into file's metadata
>      with current time
> 
>    . encode GETATTR as normal except the file size is encoded with
>      the value returned from CB_GETATTR
> 
>    . mark the file as modified
> 
> If the CB_GETATTR fails for any reasons, the delegation is recalled
> and NFS4ERR_DELAY is returned for the GETATTR.
> 
> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
> ---
>  fs/nfsd/nfs4state.c | 58 ++++++++++++++++++++++++++++++++++++
>  fs/nfsd/nfs4xdr.c   | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  fs/nfsd/state.h     |  7 +++++
>  3 files changed, 148 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 09a9e16407f9..fb305b28a090 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -127,6 +127,7 @@ static void free_session(struct nfsd4_session *);
>  
>  static const struct nfsd4_callback_ops nfsd4_cb_recall_ops;
>  static const struct nfsd4_callback_ops nfsd4_cb_notify_lock_ops;
> +static const struct nfsd4_callback_ops nfsd4_cb_getattr_ops;
>  
>  static struct workqueue_struct *laundry_wq;
>  
> @@ -1175,6 +1176,10 @@ alloc_init_deleg(struct nfs4_client *clp, struct nfs4_file *fp,
>  	dp->dl_recalled = false;
>  	nfsd4_init_cb(&dp->dl_recall, dp->dl_stid.sc_client,
>  		      &nfsd4_cb_recall_ops, NFSPROC4_CLNT_CB_RECALL);
> +	nfsd4_init_cb(&dp->dl_cb_fattr.ncf_getattr, dp->dl_stid.sc_client,
> +			&nfsd4_cb_getattr_ops, NFSPROC4_CLNT_CB_GETATTR);
> +	dp->dl_cb_fattr.ncf_file_modified = false;
> +	dp->dl_cb_fattr.ncf_cb_bmap[0] = FATTR4_WORD0_CHANGE | FATTR4_WORD0_SIZE;
>  	get_nfs4_file(fp);
>  	dp->dl_stid.sc_file = fp;
>  	return dp;
> @@ -2882,11 +2887,49 @@ nfsd4_cb_recall_any_release(struct nfsd4_callback *cb)
>  	spin_unlock(&nn->client_lock);
>  }
>  
> +static int
> +nfsd4_cb_getattr_done(struct nfsd4_callback *cb, struct rpc_task *task)
> +{
> +	struct nfs4_cb_fattr *ncf =
> +		container_of(cb, struct nfs4_cb_fattr, ncf_getattr);
> +
> +	ncf->ncf_cb_status = task->tk_status;
> +	switch (task->tk_status) {
> +	case -NFS4ERR_DELAY:
> +		rpc_delay(task, 2 * HZ);
> +		return 0;
> +	default:
> +		return 1;
> +	}
> +}
> +
> +static void
> +nfsd4_cb_getattr_release(struct nfsd4_callback *cb)
> +{
> +	struct nfs4_cb_fattr *ncf =
> +		container_of(cb, struct nfs4_cb_fattr, ncf_getattr);
> +
> +	clear_bit(CB_GETATTR_BUSY, &ncf->ncf_cb_flags);
> +	wake_up_bit(&ncf->ncf_cb_flags, CB_GETATTR_BUSY);
> +}
> +
>  static const struct nfsd4_callback_ops nfsd4_cb_recall_any_ops = {
>  	.done		= nfsd4_cb_recall_any_done,
>  	.release	= nfsd4_cb_recall_any_release,
>  };
>  
> +static const struct nfsd4_callback_ops nfsd4_cb_getattr_ops = {
> +	.done		= nfsd4_cb_getattr_done,
> +	.release	= nfsd4_cb_getattr_release,
> +};
> +
> +void nfs4_cb_getattr(struct nfs4_cb_fattr *ncf)
> +{
> +	if (test_and_set_bit(CB_GETATTR_BUSY, &ncf->ncf_cb_flags))
> +		return;
> +	nfsd4_run_cb(&ncf->ncf_getattr);
> +}
> +
>  static struct nfs4_client *create_client(struct xdr_netobj name,
>  		struct svc_rqst *rqstp, nfs4_verifier *verf)
>  {
> @@ -5591,6 +5634,8 @@ nfs4_open_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
>  	int cb_up;
>  	int status = 0;
>  	u32 wdeleg = false;
> +	struct kstat stat;
> +	struct path path;
>  
>  	cb_up = nfsd4_cb_channel_good(oo->oo_owner.so_client);
>  	open->op_recall = 0;
> @@ -5626,6 +5671,19 @@ nfs4_open_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
>  	wdeleg = open->op_share_access & NFS4_SHARE_ACCESS_WRITE;
>  	open->op_delegate_type = wdeleg ?
>  			NFS4_OPEN_DELEGATE_WRITE : NFS4_OPEN_DELEGATE_READ;
> +	if (wdeleg) {
> +		path.mnt = currentfh->fh_export->ex_path.mnt;
> +		path.dentry = currentfh->fh_dentry;
> +		if (vfs_getattr(&path, &stat, STATX_BASIC_STATS,

I think you want (STATX_SIZE|STATX_CTIME|STATX_CHANGE_COOKIE) here
instead of BASIC_STATS. You might not get the change cookie otherwise,
even when it's supported.

> +						AT_STATX_SYNC_AS_STAT)) {
> +			nfs4_put_stid(&dp->dl_stid);
> +			destroy_delegation(dp);
> +			goto out_no_deleg;
> +		}
> +		dp->dl_cb_fattr.ncf_cur_fsize = stat.size;
> +		dp->dl_cb_fattr.ncf_initial_cinfo = nfsd4_change_attribute(&stat,
> +							d_inode(currentfh->fh_dentry));
> +	}
>  	nfs4_put_stid(&dp->dl_stid);
>  	return;
>  out_no_deleg:
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 76db2fe29624..5d7e11db8ccf 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -2920,6 +2920,77 @@ 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);
> +	list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
> +		if (fl->fl_type == F_WRLCK) {
> +			spin_unlock(&ctx->flc_lock);
> +			return fl;
> +		}
> +	}

When there is a write lease, then there cannot be any read leases, so
you don't need to walk the entire list here. Just check the first
element and see whether it's a write lease.

> +	spin_unlock(&ctx->flc_lock);
> +	return NULL;
> +}
> +
> +static __be32
> +nfs4_handle_wrdeleg_conflict(struct svc_rqst *rqstp, struct inode *inode,
> +			bool *modified, u64 *size)
> +{
> +	__be32 status;
> +	struct file_lock *fl;
> +	struct nfs4_delegation *dp;
> +	struct nfs4_cb_fattr *ncf;
> +	struct iattr attrs;
> +
> +	*modified = false;
> +	fl = nfs4_wrdeleg_filelock(rqstp, inode);
> +	if (!fl)
> +		return 0;
> +	dp = fl->fl_owner;
> +	ncf = &dp->dl_cb_fattr;
> +	if (dp->dl_recall.cb_clp == *(rqstp->rq_lease_breaker))
> +		return 0;
> +
> +	refcount_inc(&dp->dl_stid.sc_count);
> +	nfs4_cb_getattr(&dp->dl_cb_fattr);
> +	wait_on_bit(&ncf->ncf_cb_flags, CB_GETATTR_BUSY, TASK_INTERRUPTIBLE);
> +	if (ncf->ncf_cb_status) {
> +		status = nfserrno(nfsd_open_break_lease(inode, NFSD_MAY_READ));
> +		nfs4_put_stid(&dp->dl_stid);
> +		return status;
> +	}
> +	ncf->ncf_cur_fsize = ncf->ncf_cb_fsize;
> +	if (!ncf->ncf_file_modified &&
> +			(ncf->ncf_initial_cinfo != ncf->ncf_cb_change ||
> +			ncf->ncf_cur_fsize != ncf->ncf_cb_fsize)) {
> +		ncf->ncf_file_modified = true;
> +	}
> +
> +	if (ncf->ncf_file_modified) {
> +		/*
> +		 * The server would not update the file's metadata
> +		 * with the client's modified size.
> +		 * nfsd4 change attribute is constructed from ctime.
> +		 */
> +		attrs.ia_mtime = attrs.ia_ctime = current_time(inode);
> +		attrs.ia_valid = ATTR_MTIME | ATTR_CTIME;
> +		setattr_copy(&nop_mnt_idmap, inode, &attrs);
> +		mark_inode_dirty(inode);
> +		*size = ncf->ncf_cur_fsize;
> +		*modified = true;
> +	}
> +	nfs4_put_stid(&dp->dl_stid);
> +	return 0;
> +}
> +
>  /*
>   * Note: @fhp can be NULL; in this case, we might have to compose the filehandle
>   * ourselves.
> @@ -2957,6 +3028,8 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
>  		.dentry	= dentry,
>  	};
>  	struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
> +	bool file_modified;
> +	u64 size = 0;
>  
>  	BUG_ON(bmval1 & NFSD_WRITEONLY_ATTRS_WORD1);
>  	BUG_ON(!nfsd_attrs_supported(minorversion, bmval));
> @@ -2966,6 +3039,12 @@ 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),
> +						&file_modified, &size);
> +		if (status)
> +			goto out;
> +	}
>  
>  	err = vfs_getattr(&path, &stat,
>  			  STATX_BASIC_STATS | STATX_BTIME | STATX_CHANGE_COOKIE,
> @@ -3089,7 +3168,10 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
>  		p = xdr_reserve_space(xdr, 8);
>  		if (!p)
>  			goto out_resource;
> -		p = xdr_encode_hyper(p, stat.size);
> +		if (file_modified)
> +			p = xdr_encode_hyper(p, size);
> +		else
> +			p = xdr_encode_hyper(p, stat.size);
>  	}
>  	if (bmval0 & FATTR4_WORD0_LINK_SUPPORT) {
>  		p = xdr_reserve_space(xdr, 4);
> diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
> index 9fb69ed8ae80..b20b65fe89b4 100644
> --- a/fs/nfsd/state.h
> +++ b/fs/nfsd/state.h
> @@ -121,6 +121,10 @@ struct nfs4_cb_fattr {
>  	struct nfsd4_callback ncf_getattr;
>  	u32 ncf_cb_status;
>  	u32 ncf_cb_bmap[1];
> +	unsigned long ncf_cb_flags;
> +	bool ncf_file_modified;
> +	u64 ncf_initial_cinfo;
> +	u64 ncf_cur_fsize;
>  
>  	/* from CB_GETATTR reply */
>  	u64 ncf_cb_change;
> @@ -744,6 +748,9 @@ extern void nfsd4_client_record_remove(struct nfs4_client *clp);
>  extern int nfsd4_client_record_check(struct nfs4_client *clp);
>  extern void nfsd4_record_grace_done(struct nfsd_net *nn);
>  
> +/* CB_GETTTAR */
> +extern void nfs4_cb_getattr(struct nfs4_cb_fattr *ncf);
> +
>  static inline bool try_to_expire_client(struct nfs4_client *clp)
>  {
>  	cmpxchg(&clp->cl_state, NFSD4_COURTESY, NFSD4_EXPIRABLE);

-- 
Jeff Layton <jlayton@kernel.org>