[PATCH 04/11] cifs: serialize channel reconnects

[Shyam Prasad N <nspmangalore@gmail.com>]

Parallel session reconnects are prone to race conditions
that are difficult to avoid cleanly. The changes so far do
ensure that parallel reconnects eventually go through.
But that can take multiple session setups on the same channel.

Avoiding that by serializing the session setups on parallel
channels. In doing so, we should avoid such issues.

Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
---
 fs/cifs/connect.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 7b103f69432e..4ea1e51c3fa5 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -222,6 +222,11 @@ cifs_mark_tcp_ses_conns_for_reconnect(struct TCP_Server_Info *server,
 		else
 			cifs_chan_set_need_reconnect(ses, server);
 
+		cifs_dbg(FYI, "%s: channel connect bitmaps: 0x%lx 0x%lx\n",
+			 __func__,
+			 ses->chans_need_reconnect,
+			 ses->chans_in_reconnect);
+
 		/* If all channels need reconnect, then tcon needs reconnect */
 		if (!mark_smb_session && !CIFS_ALL_CHANS_NEED_RECONNECT(ses)) {
 			spin_unlock(&ses->chan_lock);
@@ -3744,6 +3749,11 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
 	retries = 5;
 
 	spin_lock(&ses->ses_lock);
+	cifs_dbg(FYI, "%s: channel connect bitmaps: 0x%lx 0x%lx\n",
+		 __func__,
+		 ses->chans_need_reconnect,
+		 ses->chans_in_reconnect);
+
 	if (ses->ses_status != SES_GOOD &&
 	    ses->ses_status != SES_NEW &&
 	    ses->ses_status != SES_NEED_RECON) {
@@ -3762,11 +3772,11 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
 	}
 
 	/* another process is in the processs of sess setup */
-	while (cifs_chan_in_reconnect(ses, server)) {
+	while (ses->chans_in_reconnect) {
 		spin_unlock(&ses->chan_lock);
 		spin_unlock(&ses->ses_lock);
 		rc = wait_event_interruptible_timeout(ses->reconnect_q,
-						      (!cifs_chan_in_reconnect(ses, server)),
+						      (!ses->chans_in_reconnect),
 						      HZ);
 		if (rc < 0) {
 			cifs_dbg(FYI, "%s: aborting sess setup due to a received signal by the process\n",
@@ -3776,8 +3786,8 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
 		spin_lock(&ses->ses_lock);
 		spin_lock(&ses->chan_lock);
 
-		/* are we still trying to reconnect? */
-		if (!cifs_chan_in_reconnect(ses, server)) {
+		/* did the bitmask change? */
+		if (!ses->chans_in_reconnect) {
 			spin_unlock(&ses->chan_lock);
 			spin_unlock(&ses->ses_lock);
 			goto check_again;
-- 
2.34.1