fs/cifs: reopen persistent handles on reconnect

Continuous Availability features like persistent handles
require that clients reconnect their open files, not
just the sessions, soon after the network connection comes
back up, otherwise the server will throw away the state
(byte range locks, leases, deny modes) on those handles
after a timeout.

Add code to reconnect handles when use_persistent set
(e.g. Continuous Availability shares) after tree reconnect.
Signed-off-by: Aurelien Aptel <aaptel@suse.com>
Reviewed-by: Germano Percossi <germano.percossi@citrix.com>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/cifsproto.h

@@ -193,6 +193,8 @@ extern struct smb_vol *cifs_get_volume_info(char *mount_data,
 extern int cifs_mount(struct cifs_sb_info *, struct smb_vol *);
 extern void cifs_umount(struct cifs_sb_info *);
 extern void cifs_mark_open_files_invalid(struct cifs_tcon *tcon);
+extern void cifs_reopen_persistent_handles(struct cifs_tcon *tcon);
+
 extern bool cifs_find_lock_conflict(struct cifsFileInfo *cfile, __u64 offset,
 				    __u64 length, __u8 type,
 				    struct cifsLockInfo **conf_lock,

fs/cifs/file.c

@@ -760,6 +760,24 @@ int cifs_close(struct inode *inode, struct file *file)
 	return 0;
 }
 
+void
+cifs_reopen_persistent_handles(struct cifs_tcon *tcon)
+{
+	struct cifsFileInfo *open_file = NULL;
+	struct list_head *tmp;
+	struct list_head *tmp1;
+
+	/* list all files open on tree connection, reopen resilient handles  */
+	spin_lock(&tcon->open_file_lock);
+	list_for_each_safe(tmp, tmp1, &tcon->openFileList) {
+		open_file = list_entry(tmp, struct cifsFileInfo, tlist);
+		spin_unlock(&tcon->open_file_lock);
+		cifs_reopen_file(open_file, false /* do not flush */);
+		spin_lock(&tcon->open_file_lock);
+	}
+	spin_unlock(&tcon->open_file_lock);
+}
+
 int cifs_closedir(struct inode *inode, struct file *file)
 {
 	int rc = 0;

fs/cifs/smb2pdu.c

@@ -250,8 +250,13 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon)
 	}
 
 	cifs_mark_open_files_invalid(tcon);
+
 	rc = SMB2_tcon(0, tcon->ses, tcon->treeName, tcon, nls_codepage);
 	mutex_unlock(&tcon->ses->session_mutex);
+
+	if (tcon->use_persistent)
+		cifs_reopen_persistent_handles(tcon);
+
 	cifs_dbg(FYI, "reconnect tcon rc = %d\n", rc);
 	if (rc)
 		goto out;