This is a note to let you know that I've just added the patch titled cifs: do not share tcons with DFS to the 5.6-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: cifs-do-not-share-tcons-with-dfs.patch and it can be found in the queue-5.6 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 6b0ac19437a54bd6280a0dd2fc94e850519e8a68 Author: Paulo Alcantara <pc@xxxxxx> Date: Mon Apr 20 19:42:57 2020 -0300 cifs: do not share tcons with DFS [ Upstream commit 65303de829dd6d291a4947c1a31de31896f8a060 ] This disables tcon re-use for DFS shares. tcon->dfs_path stores the path that the tcon should connect to when doing failing over. If that tcon is used multiple times e.g. 2 mounts using it with different prefixpath, each will need a different dfs_path but there is only one tcon. The other solution would be to split the tcon in 2 tcons during failover but that is much harder. tcons could not be shared with DFS in cifs.ko because in a DFS namespace like: //domain/dfsroot -> /serverA/dfsroot, /serverB/dfsroot //serverA/dfsroot/link -> /serverA/target1/aa/bb //serverA/dfsroot/link2 -> /serverA/target1/cc/dd you can see that link and link2 are two DFS links that both resolve to the same target share (/serverA/target1), so cifs.ko will only contain a single tcon for both link and link2. The problem with that is, if we (auto)mount "link" and "link2", cifs.ko will only contain a single tcon for both DFS links so we couldn't perform failover or refresh the DFS cache for both links because tcon->dfs_path was set to either "link" or "link2", but not both -- which is wrong. Signed-off-by: Paulo Alcantara (SUSE) <pc@xxxxxx> Reviewed-by: Aurelien Aptel <aaptel@xxxxxxxx> Reviewed-by: Ronnie Sahlberg <lsahlber@xxxxxxxxxx> Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index d4a23b48e24d8..9c614d6916c2d 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -3419,6 +3419,10 @@ cifs_find_tcon(struct cifs_ses *ses, struct smb_vol *volume_info) spin_lock(&cifs_tcp_ses_lock); list_for_each(tmp, &ses->tcon_list) { tcon = list_entry(tmp, struct cifs_tcon, tcon_list); +#ifdef CONFIG_CIFS_DFS_UPCALL + if (tcon->dfs_path) + continue; +#endif if (!match_tcon(tcon, volume_info)) continue; ++tcon->tc_count;