[PATCH 09/14] cifs: add a back pointer to cifs_sb from tcon

[nspmangalore@gmail.com]

From: Shyam Prasad N <sprasad@microsoft.com>

Today, we have no way to access the cifs_sb when we
just have pointers to struct tcon. This is very
limiting as many functions deal with cifs_sb, and
these calls do not directly originate from VFS.

This change introduces a new cifs_sb field in cifs_tcon
that points to the cifs_sb for the tcon. The assumption
here is that a tcon will always map to this cifs_sb and
will never change.

Also, refcounting should not be necessary, since cifs_sb
will never be freed before tcon.

Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
---
 fs/smb/client/cifsglob.h | 1 +
 fs/smb/client/connect.c  | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index 81e7a45f413d..cdbc2cd207dc 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -1134,6 +1134,7 @@ struct cifs_tcon {
 	int tc_count;
 	struct list_head rlist; /* reconnect list */
 	spinlock_t tc_lock;  /* protect anything here that is not protected */
+	struct cifs_sb_info *cifs_sb; /* back pointer to cifs super block */
 	atomic_t num_local_opens;  /* num of all opens including disconnected */
 	atomic_t num_remote_opens; /* num of all network opens on server */
 	struct list_head openFileList;
diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
index 8393977e21ee..184075da5c6e 100644
--- a/fs/smb/client/connect.c
+++ b/fs/smb/client/connect.c
@@ -3355,6 +3355,7 @@ int cifs_mount_get_tcon(struct cifs_mount_ctx *mnt_ctx)
 		tcon = NULL;
 		goto out;
 	}
+	tcon->cifs_sb = cifs_sb;
 
 	/* if new SMB3.11 POSIX extensions are supported do not remap / and \ */
 	if (tcon->posix_extensions)
@@ -3986,6 +3987,7 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
 		cifs_put_smb_ses(ses);
 		goto out;
 	}
+	tcon->cifs_sb = cifs_sb;
 
 #ifdef CONFIG_CIFS_ALLOW_INSECURE_LEGACY
 	if (cap_unix(ses))
-- 
2.34.1