NFSD: Revert 6c41d9a

For some reason, the wait_on_bit() in nfsd4_deleg_getattr_conflict()
is waiting forever, preventing a clean server shutdown. The
requesting client might also hang waiting for a reply to the
conflicting GETATTR.

Invoking wait_on_bit() in an nfsd thread context is a hazard. The
correct fix is to replace this wait_on_bit() call site with a
mechanism that defers the conflicting GETATTR until the CB_GETATTR
completes or is known to have failed.

That will require some surgery and extended testing and it's late
in the v6.7-rc cycle, so I'm reverting now in favor of trying again
in a subsequent kernel release.

This is my fault: I should have recognized the ramifications of
calling wait_on_bit() in here before accepting this patch.

Thanks to Dai Ngo <dai.ngo@oracle.com> for diagnosing the issue.

Reported-by: Wolfgang Walter <linux-nfs@stwm.de>
Closes: https://lore.kernel.org/linux-nfs/e3d43ecdad554fbdcaa7181833834f78@stwm.de/
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Author: chucklever

fs/nfsd/nfs4state.c

@@ -127,7 +127,6 @@ 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;
 
@@ -1190,10 +1189,6 @@ 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;
@@ -2901,56 +2896,11 @@ 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);
-	struct nfs4_delegation *dp =
-			container_of(ncf, struct nfs4_delegation, dl_cb_fattr);
-
-	nfs4_put_stid(&dp->dl_stid);
-	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)
-{
-	struct nfs4_delegation *dp =
-			container_of(ncf, struct nfs4_delegation, dl_cb_fattr);
-
-	if (test_and_set_bit(CB_GETATTR_BUSY, &ncf->ncf_cb_flags))
-		return;
-	refcount_inc(&dp->dl_stid.sc_count);
-	nfsd4_run_cb(&ncf->ncf_getattr);
-}
-
 static struct nfs4_client *create_client(struct xdr_netobj name,
 		struct svc_rqst *rqstp, nfs4_verifier *verf)
 {
@@ -5686,8 +5636,6 @@ nfs4_open_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
 	struct svc_fh *parent = NULL;
 	int cb_up;
 	int status = 0;
-	struct kstat stat;
-	struct path path;
 
 	cb_up = nfsd4_cb_channel_good(oo->oo_owner.so_client);
 	open->op_recall = false;
@@ -5725,18 +5673,6 @@ nfs4_open_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
 	if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE) {
 		open->op_delegate_type = NFS4_OPEN_DELEGATE_WRITE;
 		trace_nfsd_deleg_write(&dp->dl_stid.sc_stateid);
-		path.mnt = currentfh->fh_export->ex_path.mnt;
-		path.dentry = currentfh->fh_dentry;
-		if (vfs_getattr(&path, &stat,
-				(STATX_SIZE | STATX_CTIME | STATX_CHANGE_COOKIE),
-				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));
 	} else {
 		open->op_delegate_type = NFS4_OPEN_DELEGATE_READ;
 		trace_nfsd_deleg_read(&dp->dl_stid.sc_stateid);
@@ -8489,8 +8425,6 @@ nfsd4_get_writestateid(struct nfsd4_compound_state *cstate,
  * nfsd4_deleg_getattr_conflict - Recall if GETATTR causes conflict
  * @rqstp: RPC transaction context
  * @inode: file to be checked for a conflict
- * @modified: return true if file was modified
- * @size: new size of file if modified is true
  *
  * This function is called when there is a conflict between a write
  * delegation and a change/size GETATTR from another client. The server
@@ -8499,23 +8433,21 @@ nfsd4_get_writestateid(struct nfsd4_compound_state *cstate,
  * delegation before replying to the GETATTR. See RFC 8881 section
  * 18.7.4.
  *
+ * The current implementation does not support CB_GETATTR yet. However
+ * this can avoid recalling the delegation could be added in follow up
+ * work.
+ *
  * Returns 0 if there is no conflict; otherwise an nfs_stat
  * code is returned.
  */
 __be32
-nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp, struct inode *inode,
-			     bool *modified, u64 *size)
+nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp, struct inode *inode)
 {
+	__be32 status;
 	struct file_lock_context *ctx;
-	struct nfs4_delegation *dp;
-	struct nfs4_cb_fattr *ncf;
 	struct file_lock *fl;
-	struct iattr attrs;
-	__be32 status;
-
-	might_sleep();
+	struct nfs4_delegation *dp;
 
-	*modified = false;
 	ctx = locks_inode_context(inode);
 	if (!ctx)
 		return 0;
@@ -8542,34 +8474,10 @@ nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp, struct inode *inode,
 break_lease:
 			spin_unlock(&ctx->flc_lock);
 			nfsd_stats_wdeleg_getattr_inc();
-
-			dp = fl->fl_owner;
-			ncf = &dp->dl_cb_fattr;
-			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));
-				if (status != nfserr_jukebox ||
-						!nfsd_wait_for_delegreturn(rqstp, inode))
-					return status;
-			}
-			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.
-				 */
-				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);
-				ncf->ncf_cur_fsize = ncf->ncf_cb_fsize;
-				*size = ncf->ncf_cur_fsize;
-				*modified = true;
-			}
+			status = nfserrno(nfsd_open_break_lease(inode, NFSD_MAY_READ));
+			if (status != nfserr_jukebox ||
+					!nfsd_wait_for_delegreturn(rqstp, inode))
+				return status;
 			return 0;
 		}
 		break;

fs/nfsd/nfs4xdr.c

@@ -3505,9 +3505,7 @@ nfsd4_encode_fattr4(struct svc_rqst *rqstp, struct xdr_stream *xdr,
 		u32		attrmask[3];
 		unsigned long	mask[2];
 	} u;
-	bool file_modified;
 	unsigned long bit;
-	u64 size = 0;
 
 	WARN_ON_ONCE(bmval[1] & NFSD_WRITEONLY_ATTRS_WORD1);
 	WARN_ON_ONCE(!nfsd_attrs_supported(minorversion, bmval));
@@ -3534,8 +3532,7 @@ nfsd4_encode_fattr4(struct svc_rqst *rqstp, struct xdr_stream *xdr,
 	}
 	args.size = 0;
 	if (u.attrmask[0] & (FATTR4_WORD0_CHANGE | FATTR4_WORD0_SIZE)) {
-		status = nfsd4_deleg_getattr_conflict(rqstp, d_inode(dentry),
-						      &file_modified, &size);
+		status = nfsd4_deleg_getattr_conflict(rqstp, d_inode(dentry));
 		if (status)
 			goto out;
 	}
@@ -3545,7 +3542,7 @@ nfsd4_encode_fattr4(struct svc_rqst *rqstp, struct xdr_stream *xdr,
 			  AT_STATX_SYNC_AS_STAT);
 	if (err)
 		goto out_nfserr;
-	args.size = file_modified ? size : args.stat.size;
+	args.size = args.stat.size;
 
 	if (!(args.stat.result_mask & STATX_BTIME))
 		/* underlying FS does not offer btime so we can't share it */

fs/nfsd/state.h

@@ -125,16 +125,8 @@ struct nfs4_cb_fattr {
 	/* from CB_GETATTR reply */
 	u64 ncf_cb_change;
 	u64 ncf_cb_fsize;
-
-	unsigned long ncf_cb_flags;
-	bool ncf_file_modified;
-	u64 ncf_initial_cinfo;
-	u64 ncf_cur_fsize;
 };
 
-/* bits for ncf_cb_flags */
-#define	CB_GETATTR_BUSY		0
-
 /*
  * Represents a delegation stateid. The nfs4_client holds references to these
  * and they are put when it is being destroyed or when the delegation is
@@ -754,6 +746,5 @@ static inline bool try_to_expire_client(struct nfs4_client *clp)
 }
 
 extern __be32 nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp,
-		struct inode *inode, bool *file_modified, u64 *size);
-extern void nfs4_cb_getattr(struct nfs4_cb_fattr *ncf);
+				struct inode *inode);
 #endif   /* NFSD4_STATE_H */