nfsd: take struct file setup fully into nfs4_preprocess_stateid_op

This patch changes nfs4_preprocess_stateid_op so it always returns
a valid struct file if it has been asked for that. For that we
now allocate a temporary struct file for special stateids, and check
permissions if we got the file structure from the stateid. This
ensures that all callers will get their handling of special stateids
right, and avoids code duplication.

There is a little wart in here because the read code needs to know
if we allocated a file structure so that it can copy around the
read-ahead parameters. In the long run we should probably aim to
cache full file structures used with special stateids instead.

Signed-off-by: Christoph Hellwig <[e-mail]>
Signed-off-by: J. Bruce Fields <[e-mail]>

fs/nfsd/nfs4proc.c

···
 {
 	__be32 status;
 
-	/* no need to check permission - this will be done in nfsd_read() */
-
 	read->rd_filp = NULL;
 	if (read->rd_offset >= OFFSET_MAX)
 		return nfserr_inval;
···
 		clear_bit(RQ_SPLICE_OK, &rqstp->rq_flags);
 
 	/* check stateid */
-	if ((status = nfs4_preprocess_stateid_op(SVC_NET(rqstp),
-						 cstate, &read->rd_stateid,
-						 RD_STATE, &read->rd_filp))) {
+	status = nfs4_preprocess_stateid_op(rqstp, cstate, &read->rd_stateid,
+			RD_STATE, &read->rd_filp, &read->rd_tmp_file);
+	if (status) {
 		dprintk("NFSD: nfsd4_read: couldn't process stateid!\n");
 		goto out;
 	}
···
 	int err;
 
 	if (setattr->sa_iattr.ia_valid & ATTR_SIZE) {
-		status = nfs4_preprocess_stateid_op(SVC_NET(rqstp), cstate,
-			&setattr->sa_stateid, WR_STATE, NULL);
+		status = nfs4_preprocess_stateid_op(rqstp, cstate,
+			&setattr->sa_stateid, WR_STATE, NULL, NULL);
 		if (status) {
 			dprintk("NFSD: nfsd4_setattr: couldn't process stateid!\n");
 			return status;
···
 	unsigned long cnt;
 	int nvecs;
 
-	/* no need to check permission - this will be done in nfsd_write() */
-
 	if (write->wr_offset >= OFFSET_MAX)
 		return nfserr_inval;
 
-	status = nfs4_preprocess_stateid_op(SVC_NET(rqstp),
-					cstate, stateid, WR_STATE, &filp);
+	status = nfs4_preprocess_stateid_op(rqstp, cstate, stateid, WR_STATE,
+			&filp, NULL);
 	if (status) {
 		dprintk("NFSD: nfsd4_write: couldn't process stateid!\n");
 		return status;
···
 	nvecs = fill_in_write_vector(rqstp->rq_vec, write);
 	WARN_ON_ONCE(nvecs > ARRAY_SIZE(rqstp->rq_vec));
 
-	status =  nfsd_write(rqstp, &cstate->current_fh, filp,
-			     write->wr_offset, rqstp->rq_vec, nvecs,
-			     &cnt, &write->wr_how_written);
-	if (filp)
-		fput(filp);
+	status = nfsd_vfs_write(rqstp, &cstate->current_fh, filp,
+				write->wr_offset, rqstp->rq_vec, nvecs, &cnt,
+				&write->wr_how_written);
+	fput(filp);
 
 	write->wr_bytes_written = cnt;
 
···
 	__be32 status = nfserr_notsupp;
 	struct file *file;
 
-	status = nfs4_preprocess_stateid_op(SVC_NET(rqstp), cstate,
+	status = nfs4_preprocess_stateid_op(rqstp, cstate,
 					    &fallocate->falloc_stateid,
-					    WR_STATE, &file);
+					    WR_STATE, &file, NULL);
 	if (status != nfs_ok) {
 		dprintk("NFSD: nfsd4_fallocate: couldn't process stateid!\n");
 		return status;
 	}
-	if (!file)
-		return nfserr_bad_stateid;
 
 	status = nfsd4_vfs_fallocate(rqstp, &cstate->current_fh, file,
 				     fallocate->falloc_offset,
···
 	__be32 status;
 	struct file *file;
 
-	status = nfs4_preprocess_stateid_op(SVC_NET(rqstp), cstate,
+	status = nfs4_preprocess_stateid_op(rqstp, cstate,
 					    &seek->seek_stateid,
-					    RD_STATE, &file);
+					    RD_STATE, &file, NULL);
 	if (status) {
 		dprintk("NFSD: nfsd4_seek: couldn't process stateid!\n");
 		return status;
 	}
-	if (!file)
-		return nfserr_bad_stateid;
 
 	switch (seek->seek_whence) {
 	case NFS4_CONTENT_DATA:

fs/nfsd/nfs4state.c

···
 static struct file *
 nfs4_find_file(struct nfs4_stid *s, int flags)
 {
+	if (!s)
+		return NULL;
+
 	switch (s->sc_type) {
 	case NFS4_DELEG_STID:
 		if (WARN_ON_ONCE(!s->sc_file->fi_deleg_file))
···
 	return nfs4_check_openmode(ols, flags);
 }
 
+static __be32
+nfs4_check_file(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfs4_stid *s,
+		struct file **filpp, bool *tmp_file, int flags)
+{
+	int acc = (flags & RD_STATE) ? NFSD_MAY_READ : NFSD_MAY_WRITE;
+	struct file *file;
+	__be32 status;
+
+	file = nfs4_find_file(s, flags);
+	if (file) {
+		status = nfsd_permission(rqstp, fhp->fh_export, fhp->fh_dentry,
+				acc | NFSD_MAY_OWNER_OVERRIDE);
+		if (status) {
+			fput(file);
+			return status;
+		}
+
+		*filpp = file;
+	} else {
+		status = nfsd_open(rqstp, fhp, S_IFREG, acc, filpp);
+		if (status)
+			return status;
+
+		if (tmp_file)
+			*tmp_file = true;
+	}
+
+	return 0;
+}
+
 /*
  * Checks for stateid operations
  */
 __be32
-nfs4_preprocess_stateid_op(struct net *net, struct nfsd4_compound_state *cstate,
-			   stateid_t *stateid, int flags, struct file **filpp)
+nfs4_preprocess_stateid_op(struct svc_rqst *rqstp,
+		struct nfsd4_compound_state *cstate, stateid_t *stateid,
+		int flags, struct file **filpp, bool *tmp_file)
 {
 	struct svc_fh *fhp = &cstate->current_fh;
 	struct inode *ino = d_inode(fhp->fh_dentry);
+	struct net *net = SVC_NET(rqstp);
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
-	struct nfs4_stid *s;
+	struct nfs4_stid *s = NULL;
 	__be32 status;
 
 	if (filpp)
 		*filpp = NULL;
+	if (tmp_file)
+		*tmp_file = false;
 
 	if (grace_disallows_io(net, ino))
 		return nfserr_grace;
 
-	if (ZERO_STATEID(stateid) || ONE_STATEID(stateid))
-		return check_special_stateids(net, fhp, stateid, flags);
+	if (ZERO_STATEID(stateid) || ONE_STATEID(stateid)) {
+		status = check_special_stateids(net, fhp, stateid, flags);
+		goto done;
+	}
 
 	status = nfsd4_lookup_stateid(cstate, stateid,
 				NFS4_DELEG_STID|NFS4_OPEN_STID|NFS4_LOCK_STID,
···
 		break;
 	}
 
-	if (!status && filpp) {
-		*filpp = nfs4_find_file(s, flags);
-		if (!*filpp)
-			status = nfserr_serverfault;
-	}
+done:
+	if (!status && filpp)
+		status = nfs4_check_file(rqstp, fhp, s, filpp, tmp_file, flags);
 out:
-	nfs4_put_stid(s);
+	if (s)
+		nfs4_put_stid(s);
 	return status;
 }
 

fs/nfsd/nfs4xdr.c

···
  *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#include <linux/file.h>
 #include <linux/slab.h>
 #include <linux/namei.h>
 #include <linux/statfs.h>
···
 	unsigned long maxcount;
 	struct xdr_stream *xdr = &resp->xdr;
 	struct file *file = read->rd_filp;
-	struct svc_fh *fhp = read->rd_fhp;
 	int starting_len = xdr->buf->len;
 	struct raparms *ra = NULL;
 	__be32 *p;
···
 	maxcount = min_t(unsigned long, maxcount, (xdr->buf->buflen - xdr->buf->len));
 	maxcount = min_t(unsigned long, maxcount, read->rd_length);
 
-	if (read->rd_filp) {
-		err = nfsd_permission(resp->rqstp, fhp->fh_export,
-				fhp->fh_dentry,
-				NFSD_MAY_READ|NFSD_MAY_OWNER_OVERRIDE);
-		if (err)
-			goto err_truncate;
-	} else {
-		err = nfsd_open(resp->rqstp, fhp, S_IFREG, NFSD_MAY_READ,
-				&file);
-		if (err)
-			goto err_truncate;
-
+	if (read->rd_tmp_file)
 		ra = nfsd_init_raparms(file);
-	}
 
 	if (file->f_op->splice_read && test_bit(RQ_SPLICE_OK, &resp->rqstp->rq_flags))
 		err = nfsd4_encode_splice_read(resp, read, file, maxcount);
···
 
 	if (ra)
 		nfsd_put_raparams(file, ra);
-	if (!read->rd_filp)
-		fput(file);
 
-err_truncate:
 	if (err)
 		xdr_truncate_encode(xdr, starting_len);
 	return err;

fs/nfsd/state.h

···
 struct nfsd4_compound_state;
 struct nfsd_net;
 
-extern __be32 nfs4_preprocess_stateid_op(struct net *net,
-		struct nfsd4_compound_state *cstate,
-		stateid_t *stateid, int flags, struct file **filp);
+extern __be32 nfs4_preprocess_stateid_op(struct svc_rqst *rqstp,
+		struct nfsd4_compound_state *cstate, stateid_t *stateid,
+		int flags, struct file **filp, bool *tmp_file);
 __be32 nfsd4_lookup_stateid(struct nfsd4_compound_state *cstate,
 		     stateid_t *stateid, unsigned char typemask,
 		     struct nfs4_stid **s, struct nfsd_net *nn);

fs/nfsd/vfs.c

···
 			   struct file *file, loff_t offset, loff_t len,
 			   int flags)
 {
-	__be32 err;
 	int error;
 
 	if (!S_ISREG(file_inode(file)->i_mode))
 		return nfserr_inval;
-
-	err = nfsd_permission(rqstp, fhp->fh_export, fhp->fh_dentry, NFSD_MAY_WRITE);
-	if (err)
-		return err;
 
 	error = vfs_fallocate(file, flags, offset, len);
 	if (!error)
···
 	return err;
 }
 
-static __be32
+__be32
 nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
 				loff_t offset, struct kvec *vec, int vlen,
 				unsigned long *cnt, int *stablep)

fs/nfsd/vfs.h

···
 				loff_t, struct kvec *, int, unsigned long *);
 __be32 		nfsd_write(struct svc_rqst *, struct svc_fh *,struct file *,
 				loff_t, struct kvec *,int, unsigned long *, int *);
+__be32		nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp,
+				struct file *file, loff_t offset,
+				struct kvec *vec, int vlen, unsigned long *cnt,
+				int *stablep);
 __be32		nfsd_readlink(struct svc_rqst *, struct svc_fh *,
 				char *, int *);
 __be32		nfsd_symlink(struct svc_rqst *, struct svc_fh *,

fs/nfsd/xdr4.h

···
 	u32		rd_length;          /* request */
 	int		rd_vlen;
 	struct file     *rd_filp;
+	bool		rd_tmp_file;
 	
 	struct svc_rqst *rd_rqstp;          /* response */
 	struct svc_fh * rd_fhp;             /* response */