smb3: fix unusable share after force unmount failure

commit 491eafce1a51c457701351a4bf40733799745314 upstream.

If user does forced unmount ("umount -f") while files are still open
on the share (as was seen in a Kubernetes example running on SMB3.1.1
mount) then we were marking the share as "TID_EXITING" in umount_begin()
which caused all subsequent operations (except write) to fail ... but
unfortunately when umount_begin() is called we do not know yet that
there are open files or active references on the share that would prevent
unmount from succeeding.  Kubernetes had example when they were doing
umount -f when files were open which caused the share to become
unusable until the files were closed (and the umount retried).

Fix this so that TID_EXITING is not set until we are about to send
the tree disconnect (not at the beginning of forced umounts in
umount_begin) so that if "umount -f" fails (due to open files or
references) the mount is still usable.

Cc: stable@vger.kernel.org
Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>
Reviewed-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 11 insertions, 13 deletions

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 6094cb2ff099..03e3e95cf25b 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -730,13 +730,16 @@ static void cifs_umount_begin(struct super_block *sb)
 	spin_lock(&tcon->tc_lock);
 	if ((tcon->tc_count > 1) || (tcon->status == TID_EXITING)) {
 		/* we have other mounts to same share or we have
-		   already tried to force umount this and woken up
+		   already tried to umount this and woken up
 		   all waiting network requests, nothing to do */
 		spin_unlock(&tcon->tc_lock);
 		spin_unlock(&cifs_tcp_ses_lock);
 		return;
-	} else if (tcon->tc_count == 1)
-		tcon->status = TID_EXITING;
+	}
+	/*
+	 * can not set tcon->status to TID_EXITING yet since we don't know if umount -f will
+	 * fail later (e.g. due to open files).  TID_EXITING will be set just before tdis req sent
+	 */
 	spin_unlock(&tcon->tc_lock);
 	spin_unlock(&cifs_tcp_ses_lock);
 
diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 6b8f59912f70..6c6a7fc47f3e 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -85,13 +85,11 @@ cifs_reconnect_tcon(struct cifs_tcon *tcon, int smb_command)
 
 	/*
 	 * only tree disconnect, open, and write, (and ulogoff which does not
-	 * have tcon) are allowed as we start force umount
+	 * have tcon) are allowed as we start umount
 	 */
 	spin_lock(&tcon->tc_lock);
 	if (tcon->status == TID_EXITING) {
-		if (smb_command != SMB_COM_WRITE_ANDX &&
-		    smb_command != SMB_COM_OPEN_ANDX &&
-		    smb_command != SMB_COM_TREE_DISCONNECT) {
+		if (smb_command != SMB_COM_TREE_DISCONNECT) {
 			spin_unlock(&tcon->tc_lock);
 			cifs_dbg(FYI, "can not send cmd %d while umounting\n",
 				 smb_command);
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 0006b1ca0203..ecc1455358cc 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -2365,6 +2365,7 @@ cifs_put_tcon(struct cifs_tcon *tcon)
 	WARN_ON(tcon->tc_count < 0);
 
 	list_del_init(&tcon->tcon_list);
+	tcon->status = TID_EXITING;
 	spin_unlock(&tcon->tc_lock);
 	spin_unlock(&cifs_tcp_ses_lock);
 
diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 23926f754d2a..c1aba3dd5d34 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -225,13 +225,9 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon,
 	spin_lock(&tcon->tc_lock);
 	if (tcon->status == TID_EXITING) {
 		/*
-		 * only tree disconnect, open, and write,
-		 * (and ulogoff which does not have tcon)
-		 * are allowed as we start force umount.
+		 * only tree disconnect allowed when disconnecting ...
 		 */
-		if ((smb2_command != SMB2_WRITE) &&
-		   (smb2_command != SMB2_CREATE) &&
-		   (smb2_command != SMB2_TREE_DISCONNECT)) {
+		if (smb2_command != SMB2_TREE_DISCONNECT) {
 			spin_unlock(&tcon->tc_lock);
 			cifs_dbg(FYI, "can not send cmd %d while umounting\n",
 				 smb2_command);