three small smb3 client fixes

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Merge tag '6.3-rc7-smb3-client-fixes' of git://git.samba.org/sfrench/cifs-2.6

Pull cifs fixes from Steve French:
 "Three small smb3 client fixes:

   - two important fixes for unbuffered read regression with the
     iov_iter changes (e.g. read soon after mount in some multichannel
     scenarios)

   - DFS prefix path fix (also for stable)"

* tag '6.3-rc7-smb3-client-fixes' of git://git.samba.org/sfrench/cifs-2.6:
  cifs: Reapply lost fix from commit 30b2b2196d
  cifs: Fix unbuffered read
  cifs: avoid dup prefix path in dfs_get_automount_devname()

fs/cifs/cifs_dfs_ref.c

@@ -171,8 +171,6 @@ static struct vfsmount *cifs_dfs_do_automount(struct path *path)
 		mnt = ERR_CAST(full_path);
 		goto out;
 	}
-
-	convert_delimiter(full_path, '/');
 	cifs_dbg(FYI, "%s: full_path: %s\n", __func__, full_path);
 
 	tmp = *cur_ctx;

fs/cifs/dfs.h

@@ -34,19 +34,33 @@ static inline int dfs_get_referral(struct cifs_mount_ctx *mnt_ctx, const char *p
 			      cifs_remap(cifs_sb), path, ref, tl);
 }
 
+/* Return DFS full path out of a dentry set for automount */
 static inline char *dfs_get_automount_devname(struct dentry *dentry, void *page)
 {
 	struct cifs_sb_info *cifs_sb = CIFS_SB(dentry->d_sb);
 	struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
 	struct TCP_Server_Info *server = tcon->ses->server;
+	size_t len;
+	char *s;
 
 	if (unlikely(!server->origin_fullpath))
 		return ERR_PTR(-EREMOTE);
 
-	return __build_path_from_dentry_optional_prefix(dentry, page,
-							server->origin_fullpath,
-							strlen(server->origin_fullpath),
-							true);
+	s = dentry_path_raw(dentry, page, PATH_MAX);
+	if (IS_ERR(s))
+		return s;
+	/* for root, we want "" */
+	if (!s[1])
+		s++;
+
+	len = strlen(server->origin_fullpath);
+	if (s < (char *)page + len)
+		return ERR_PTR(-ENAMETOOLONG);
+
+	s -= len;
+	memcpy(s, server->origin_fullpath, len);
+	convert_delimiter(s, '/');
+	return s;
 }
 
 static inline void dfs_put_root_smb_sessions(struct list_head *head)

fs/cifs/file.c

@@ -4010,7 +4010,6 @@ static void
 collect_uncached_read_data(struct cifs_aio_ctx *ctx)
 {
 	struct cifs_readdata *rdata, *tmp;
-	struct iov_iter *to = &ctx->iter;
 	struct cifs_sb_info *cifs_sb;
 	int rc;
 
@@ -4076,9 +4075,6 @@ again:
 		kref_put(&rdata->refcount, cifs_readdata_release);
 	}
 
-	if (!ctx->direct_io)
-		ctx->total_len = ctx->len - iov_iter_count(to);
-
 	/* mask nodata case */
 	if (rc == -ENODATA)
 		rc = 0;

fs/cifs/smb2pdu.c

@@ -4180,10 +4180,12 @@ smb2_readv_callback(struct mid_q_entry *mid)
 	struct smb2_hdr *shdr =
 				(struct smb2_hdr *)rdata->iov[0].iov_base;
 	struct cifs_credits credits = { .value = 0, .instance = 0 };
-	struct smb_rqst rqst = { .rq_iov = &rdata->iov[1],
-				 .rq_nvec = 1,
-				 .rq_iter = rdata->iter,
-				 .rq_iter_size = iov_iter_count(&rdata->iter), };
+	struct smb_rqst rqst = { .rq_iov = &rdata->iov[1], .rq_nvec = 1 };
+
+	if (rdata->got_bytes) {
+		rqst.rq_iter	  = rdata->iter;
+		rqst.rq_iter_size = iov_iter_count(&rdata->iter);
+	};
 
 	WARN_ONCE(rdata->server != mid->server,
 		  "rdata server %p != mid server %p",