cifs: add a helper to find an existing readable handle to a file

and convert smb2_query_path_info() to use it.
This will eliminate the need for a SMB2_Create when we already have an
open handle that can be used. This will also prevent a oplock break
in case the other handle holds a lease.
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifsproto.h

@@ -140,6 +140,8 @@ extern int cifs_get_writable_file(struct cifsInodeInfo *cifs_inode,
 extern int cifs_get_writable_path(struct cifs_tcon *tcon, const char *name,
 				  struct cifsFileInfo **ret_file);
 extern struct cifsFileInfo *find_readable_file(struct cifsInodeInfo *, bool);
+extern int cifs_get_readable_path(struct cifs_tcon *tcon, const char *name,
+				  struct cifsFileInfo **ret_file);
 extern unsigned int smbCalcSize(void *buf, struct TCP_Server_Info *server);
 extern int decode_negTokenInit(unsigned char *security_blob, int length,
 			struct TCP_Server_Info *server);

fs/cifs/file.c

@@ -2008,6 +2008,42 @@ cifs_get_writable_path(struct cifs_tcon *tcon, const char *name,
 	return -ENOENT;
 }
 
+int
+cifs_get_readable_path(struct cifs_tcon *tcon, const char *name,
+		       struct cifsFileInfo **ret_file)
+{
+	struct list_head *tmp;
+	struct cifsFileInfo *cfile;
+	struct cifsInodeInfo *cinode;
+	char *full_path;
+
+	*ret_file = NULL;
+
+	spin_lock(&tcon->open_file_lock);
+	list_for_each(tmp, &tcon->openFileList) {
+		cfile = list_entry(tmp, struct cifsFileInfo,
+			     tlist);
+		full_path = build_path_from_dentry(cfile->dentry);
+		if (full_path == NULL) {
+			spin_unlock(&tcon->open_file_lock);
+			return -ENOMEM;
+		}
+		if (strcmp(full_path, name)) {
+			kfree(full_path);
+			continue;
+		}
+
+		kfree(full_path);
+		cinode = CIFS_I(d_inode(cfile->dentry));
+		spin_unlock(&tcon->open_file_lock);
+		*ret_file = find_readable_file(cinode, 0);
+		return *ret_file ? 0 : -ENOENT;
+	}
+
+	spin_unlock(&tcon->open_file_lock);
+	return -ENOENT;
+}
+
 static int cifs_partialpagewrite(struct page *page, unsigned from, unsigned to)
 {
 	struct address_space *mapping = page->mapping;

fs/cifs/smb2inode.c

@@ -125,15 +125,31 @@ smb2_compound_op(const unsigned int xid, struct cifs_tcon *tcon,
 		rqst[num_rqst].rq_iov = qi_iov;
 		rqst[num_rqst].rq_nvec = 1;
 
-		rc = SMB2_query_info_init(tcon, &rqst[num_rqst], COMPOUND_FID,
-				COMPOUND_FID, FILE_ALL_INFORMATION,
+		if (cfile)
+			rc = SMB2_query_info_init(tcon, &rqst[num_rqst],
+				cfile->fid.persistent_fid,
+				cfile->fid.volatile_fid,
+				FILE_ALL_INFORMATION,
 				SMB2_O_INFO_FILE, 0,
 				sizeof(struct smb2_file_all_info) +
 					  PATH_MAX * 2, 0, NULL);
+		else {
+			rc = SMB2_query_info_init(tcon, &rqst[num_rqst],
+				COMPOUND_FID,
+				COMPOUND_FID,
+				 FILE_ALL_INFORMATION,
+				SMB2_O_INFO_FILE, 0,
+				sizeof(struct smb2_file_all_info) +
+					  PATH_MAX * 2, 0, NULL);
+			if (!rc) {
+				smb2_set_next_command(tcon, &rqst[num_rqst]);
+				smb2_set_related(&rqst[num_rqst]);
+			}
+		}
+
 		if (rc)
 			goto finished;
-		smb2_set_next_command(tcon, &rqst[num_rqst]);
-		smb2_set_related(&rqst[num_rqst++]);
+		num_rqst++;
 		trace_smb3_query_info_compound_enter(xid, ses->Suid, tcon->tid,
 						     full_path);
 		break;
@@ -421,6 +437,7 @@ smb2_query_path_info(const unsigned int xid, struct cifs_tcon *tcon,
 	__u32 create_options = 0;
 	struct cifs_fid fid;
 	bool no_cached_open = tcon->nohandlecache;
+	struct cifsFileInfo *cfile;
 
 	*adjust_tz = false;
 	*symlink = false;
@@ -452,9 +469,10 @@ smb2_query_path_info(const unsigned int xid, struct cifs_tcon *tcon,
 	if (backup_cred(cifs_sb))
 		create_options |= CREATE_OPEN_BACKUP_INTENT;
 
+	cifs_get_readable_path(tcon, full_path, &cfile);
 	rc = smb2_compound_op(xid, tcon, cifs_sb, full_path,
 			      FILE_READ_ATTRIBUTES, FILE_OPEN, create_options,
-			      smb2_data, SMB2_OP_QUERY_INFO, NULL);
+			      smb2_data, SMB2_OP_QUERY_INFO, cfile);
 	if (rc == -EOPNOTSUPP) {
 		*symlink = true;
 		create_options |= OPEN_REPARSE_POINT;