[PATCH 4/4] smb: client: serialise cifs_construct_tcon() with cifs_mount_mutex

[Paulo Alcantara <pc@manguebit.com>]

Serialise cifs_construct_tcon() with cifs_mount_mutex to handle
parallel mounts that may end up reusing the session and tcon created
by it.

Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
---
 fs/smb/client/connect.c    | 13 ++++++++++++-
 fs/smb/client/fs_context.c |  6 +++---
 fs/smb/client/fs_context.h | 12 ++++++++++++
 3 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
index cc0568c3f085..27d9f262eccb 100644
--- a/fs/smb/client/connect.c
+++ b/fs/smb/client/connect.c
@@ -3988,7 +3988,7 @@ cifs_set_vol_auth(struct smb3_fs_context *ctx, struct cifs_ses *ses)
 }
 
 static struct cifs_tcon *
-cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
+__cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
 {
 	int rc;
 	struct cifs_tcon *master_tcon = cifs_sb_master_tcon(cifs_sb);
@@ -4082,6 +4082,17 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
 	return tcon;
 }
 
+static struct cifs_tcon *
+cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
+{
+	struct cifs_tcon *ret;
+
+	cifs_mount_lock();
+	ret = __cifs_construct_tcon(cifs_sb, fsuid);
+	cifs_mount_unlock();
+	return ret;
+}
+
 struct cifs_tcon *
 cifs_sb_master_tcon(struct cifs_sb_info *cifs_sb)
 {
diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
index bdcbe6ff2739..b7bfe705b2c4 100644
--- a/fs/smb/client/fs_context.c
+++ b/fs/smb/client/fs_context.c
@@ -37,7 +37,7 @@
 #include "rfc1002pdu.h"
 #include "fs_context.h"
 
-static DEFINE_MUTEX(cifs_mount_mutex);
+DEFINE_MUTEX(cifs_mount_mutex);
 
 static const match_table_t cifs_smb_version_tokens = {
 	{ Smb_1, SMB1_VERSION_STRING },
@@ -783,9 +783,9 @@ static int smb3_get_tree(struct fs_context *fc)
 
 	if (err)
 		return err;
-	mutex_lock(&cifs_mount_mutex);
+	cifs_mount_lock();
 	ret = smb3_get_tree_common(fc);
-	mutex_unlock(&cifs_mount_mutex);
+	cifs_mount_unlock();
 	return ret;
 }
 
diff --git a/fs/smb/client/fs_context.h b/fs/smb/client/fs_context.h
index 7863f2248c4d..8a35645e0b65 100644
--- a/fs/smb/client/fs_context.h
+++ b/fs/smb/client/fs_context.h
@@ -304,4 +304,16 @@ extern void smb3_update_mnt_flags(struct cifs_sb_info *cifs_sb);
 #define MAX_CACHED_FIDS 16
 extern char *cifs_sanitize_prepath(char *prepath, gfp_t gfp);
 
+extern struct mutex cifs_mount_mutex;
+
+static inline void cifs_mount_lock(void)
+{
+	mutex_lock(&cifs_mount_mutex);
+}
+
+static inline void cifs_mount_unlock(void)
+{
+	mutex_unlock(&cifs_mount_mutex);
+}
+
 #endif
-- 
2.44.0