cifs: reinstate sharing of tree connections

Use a similar approach to the SMB session sharing. Add a list of tcons
attached to each SMB session. Move the refcount to non-atomic. Protect
all of the above with the cifs_tcp_ses_lock. Add functions to
properly find and put references to the tcons.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 62 insertions, 31 deletions

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index a3dc0d7cafc3..2f2be8faabb3 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -124,7 +124,7 @@ static int
 cifs_reconnect(struct TCP_Server_Info *server)
 {
         int rc = 0;
-        struct list_head *tmp;
+        struct list_head *tmp, *tmp2;
         struct cifsSesInfo *ses;
         struct cifsTconInfo *tcon;
         struct mid_q_entry *mid_entry;
@@ -149,13 +149,12 @@ cifs_reconnect(struct TCP_Server_Info *server)
                 ses = list_entry(tmp, struct cifsSesInfo, smb_ses_list);
                 ses->need_reconnect = true;
                 ses->ipc_tid = 0;
-        }
-        read_unlock(&cifs_tcp_ses_lock);
-        list_for_each(tmp, &GlobalTreeConnectionList) {
-                tcon = list_entry(tmp, struct cifsTconInfo, cifsConnectionList);
-                if ((tcon->ses) && (tcon->ses->server == server))
+                list_for_each(tmp2, &ses->tcon_list) {
+                        tcon = list_entry(tmp2, struct cifsTconInfo, tcon_list);
                         tcon->need_reconnect = true;
+                }
         }
+        read_unlock(&cifs_tcp_ses_lock);
         /* do not want to be sending data on a socket we are freeing */
         down(&server->tcpSem);
         if (server->ssocket) {
@@ -1462,6 +1461,52 @@ cifs_put_smb_ses(struct cifsSesInfo *ses)
         cifs_put_tcp_session(server);
 }
 
+static struct cifsTconInfo *
+cifs_find_tcon(struct cifsSesInfo *ses, const char *unc)
+{
+        struct list_head *tmp;
+        struct cifsTconInfo *tcon;
+
+        write_lock(&cifs_tcp_ses_lock);
+        list_for_each(tmp, &ses->tcon_list) {
+                tcon = list_entry(tmp, struct cifsTconInfo, tcon_list);
+                if (tcon->tidStatus == CifsExiting)
+                        continue;
+                if (strncmp(tcon->treeName, unc, MAX_TREE_SIZE))
+                        continue;
+
+                ++tcon->tc_count;
+                write_unlock(&cifs_tcp_ses_lock);
+                return tcon;
+        }
+        write_unlock(&cifs_tcp_ses_lock);
+        return NULL;
+}
+
+static void
+cifs_put_tcon(struct cifsTconInfo *tcon)
+{
+        int xid;
+        struct cifsSesInfo *ses = tcon->ses;
+
+        write_lock(&cifs_tcp_ses_lock);
+        if (--tcon->tc_count > 0) {
+                write_unlock(&cifs_tcp_ses_lock);
+                return;
+        }
+
+        list_del_init(&tcon->tcon_list);
+        write_unlock(&cifs_tcp_ses_lock);
+
+        xid = GetXid();
+        CIFSSMBTDis(xid, tcon);
+        _FreeXid(xid);
+
+        DeleteTconOplockQEntries(tcon);
+        tconInfoFree(tcon);
+        cifs_put_smb_ses(ses);
+}
+
 int
 get_dfs_path(int xid, struct cifsSesInfo *pSesInfo, const char *old_path,
              const struct nls_table *nls_codepage, unsigned int *pnum_referrals,
@@ -2220,11 +2265,11 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
         if (!rc) {
                 setup_cifs_sb(&volume_info, cifs_sb);
 
+                tcon = cifs_find_tcon(pSesInfo, volume_info.UNC);
                 if (tcon) {
                         cFYI(1, ("Found match on UNC path"));
-                        if (tcon->seal != volume_info.seal)
-                                cERROR(1, ("transport encryption setting "
-                                           "conflicts with existing tid"));
+                        /* existing tcon already has a reference */
+                        cifs_put_smb_ses(pSesInfo);
                 } else {
                         tcon = tconInfoAlloc();
                         if (tcon == NULL) {
@@ -2257,6 +2302,10 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
                         if (rc)
                                 goto mount_fail_check;
                         tcon->seal = volume_info.seal;
+                        tcon->ses = pSesInfo;
+                        write_lock(&cifs_tcp_ses_lock);
+                        list_add(&tcon->tcon_list, &pSesInfo->tcon_list);
+                        write_unlock(&cifs_tcp_ses_lock);
                 }
 
                 /* we can have only one retry value for a connection
@@ -2283,18 +2332,14 @@ mount_fail_check:
                 /* If find_unc succeeded then rc == 0 so we can not end */
                 /* up accidently freeing someone elses tcon struct */
                 if (tcon)
-                        tconInfoFree(tcon);
-
-                /* should also end up putting our tcp session ref if needed */
-                if (pSesInfo)
+                        cifs_put_tcon(tcon);
+                else if (pSesInfo)
                         cifs_put_smb_ses(pSesInfo);
                 else
                         cifs_put_tcp_session(srvTcp);
                 goto out;
         }
-        atomic_inc(&tcon->useCount);
         cifs_sb->tcon = tcon;
-        tcon->ses = pSesInfo;
 
         /* do not care if following two calls succeed - informational */
         if (!tcon->ipc) {
@@ -3565,23 +3610,10 @@ int
 cifs_umount(struct super_block *sb, struct cifs_sb_info *cifs_sb)
 {
         int rc = 0;
-        int xid;
-        struct cifsSesInfo *ses = NULL;
         char *tmp;
 
-        xid = GetXid();
-
-        if (cifs_sb->tcon) {
-                ses = cifs_sb->tcon->ses; /* save ptr to ses before delete tcon!*/
-                rc = CIFSSMBTDis(xid, cifs_sb->tcon);
-                if (rc == -EBUSY) {
-                        FreeXid(xid);
-                        return 0;
-                }
-                DeleteTconOplockQEntries(cifs_sb->tcon);
-                tconInfoFree(cifs_sb->tcon);
-                cifs_put_smb_ses(ses);
-        }
+        if (cifs_sb->tcon)
+                cifs_put_tcon(cifs_sb->tcon);
 
         cifs_sb->tcon = NULL;
         tmp = cifs_sb->prepath;
@@ -3589,7 +3621,6 @@ cifs_umount(struct super_block *sb, struct cifs_sb_info *cifs_sb)
         cifs_sb->prepath = NULL;
         kfree(tmp);
 
-        FreeXid(xid);
         return rc;
 }