smb: client: fix DFS interlink failover

The DFS interlinks point to different DFS namespaces so make sure to
use the correct DFS root server to chase any DFS links under it by
storing the SMB session in dfs_ref_walk structure and then using it on
every referral walk.

Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 35 insertions, 38 deletions

diff --git a/fs/smb/client/dfs.c b/fs/smb/client/dfs.c
index 3ec965547e3d..3f6077c68d68 100644
--- a/fs/smb/client/dfs.c
+++ b/fs/smb/client/dfs.c
@@ -69,7 +69,7 @@ static int get_session(struct cifs_mount_ctx *mnt_ctx, const char *full_path)
  * Get an active reference of @ses so that next call to cifs_put_tcon() won't
  * release it as any new DFS referrals must go through its IPC tcon.
  */
-static void add_root_smb_session(struct cifs_mount_ctx *mnt_ctx)
+static void set_root_smb_session(struct cifs_mount_ctx *mnt_ctx)
 {
 	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
 	struct cifs_ses *ses = mnt_ctx->ses;
@@ -95,7 +95,7 @@ static inline int parse_dfs_target(struct smb3_fs_context *ctx,
 	return rc;
 }
 
-static int set_ref_paths(struct cifs_mount_ctx *mnt_ctx,
+static int setup_dfs_ref(struct cifs_mount_ctx *mnt_ctx,
 			 struct dfs_info3_param *tgt,
 			 struct dfs_ref_walk *rw)
 {
@@ -120,6 +120,7 @@ static int set_ref_paths(struct cifs_mount_ctx *mnt_ctx,
 	}
 	ref_walk_path(rw) = ref_path;
 	ref_walk_fpath(rw) = full_path;
+	ref_walk_ses(rw) = ctx->dfs_root_ses;
 	return 0;
 }
 
@@ -128,11 +129,11 @@ static int __dfs_referral_walk(struct cifs_mount_ctx *mnt_ctx,
 {
 	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
 	struct dfs_info3_param tgt = {};
-	bool is_refsrv;
 	int rc = -ENOENT;
 
 again:
 	do {
+		ctx->dfs_root_ses = ref_walk_ses(rw);
 		if (ref_walk_empty(rw)) {
 			rc = dfs_get_referral(mnt_ctx, ref_walk_path(rw) + 1,
 					      NULL, ref_walk_tl(rw));
@@ -158,10 +159,7 @@ again:
 			if (rc)
 				continue;
 
-			is_refsrv = tgt.server_type == DFS_TYPE_ROOT ||
-				DFS_INTERLINK(tgt.flags);
 			ref_walk_set_tgt_hint(rw);
-
 			if (tgt.flags & DFSREF_STORAGE_SERVER) {
 				rc = cifs_mount_get_tcon(mnt_ctx);
 				if (!rc)
@@ -172,12 +170,10 @@ again:
 					continue;
 			}
 
-			if (is_refsrv)
-				add_root_smb_session(mnt_ctx);
-
+			set_root_smb_session(mnt_ctx);
 			rc = ref_walk_advance(rw);
 			if (!rc) {
-				rc = set_ref_paths(mnt_ctx, &tgt, rw);
+				rc = setup_dfs_ref(mnt_ctx, &tgt, rw);
 				if (!rc) {
 					rc = -EREMOTE;
 					goto again;
@@ -193,20 +189,22 @@ out:
 	return rc;
 }
 
-static int dfs_referral_walk(struct cifs_mount_ctx *mnt_ctx)
+static int dfs_referral_walk(struct cifs_mount_ctx *mnt_ctx,
+			     struct dfs_ref_walk **rw)
 {
-	struct dfs_ref_walk *rw;
 	int rc;
 
-	rw = ref_walk_alloc();
-	if (IS_ERR(rw))
-		return PTR_ERR(rw);
+	*rw = ref_walk_alloc();
+	if (IS_ERR(*rw)) {
+		rc = PTR_ERR(*rw);
+		*rw = NULL;
+		return rc;
+	}
 
-	ref_walk_init(rw);
-	rc = set_ref_paths(mnt_ctx, NULL, rw);
+	ref_walk_init(*rw);
+	rc = setup_dfs_ref(mnt_ctx, NULL, *rw);
 	if (!rc)
-		rc = __dfs_referral_walk(mnt_ctx, rw);
-	ref_walk_free(rw);
+		rc = __dfs_referral_walk(mnt_ctx, *rw);
 	return rc;
 }
 
@@ -214,16 +212,16 @@ static int __dfs_mount_share(struct cifs_mount_ctx *mnt_ctx)
 {
 	struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
 	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
+	struct dfs_ref_walk *rw = NULL;
 	struct cifs_tcon *tcon;
 	char *origin_fullpath;
-	bool new_tcon = true;
 	int rc;
 
 	origin_fullpath = dfs_get_path(cifs_sb, ctx->source);
 	if (IS_ERR(origin_fullpath))
 		return PTR_ERR(origin_fullpath);
 
-	rc = dfs_referral_walk(mnt_ctx);
+	rc = dfs_referral_walk(mnt_ctx, &rw);
 	if (!rc) {
 		/*
 		 * Prevent superblock from being created with any missing
@@ -241,21 +239,16 @@ static int __dfs_mount_share(struct cifs_mount_ctx *mnt_ctx)
 
 	tcon = mnt_ctx->tcon;
 	spin_lock(&tcon->tc_lock);
-	if (!tcon->origin_fullpath) {
-		tcon->origin_fullpath = origin_fullpath;
-		origin_fullpath = NULL;
-	} else {
-		new_tcon = false;
-	}
+	tcon->origin_fullpath = origin_fullpath;
+	origin_fullpath = NULL;
+	ref_walk_set_tcon(rw, tcon);
 	spin_unlock(&tcon->tc_lock);
-
-	if (new_tcon) {
-		queue_delayed_work(dfscache_wq, &tcon->dfs_cache_work,
-				   dfs_cache_get_ttl() * HZ);
-	}
+	queue_delayed_work(dfscache_wq, &tcon->dfs_cache_work,
+			   dfs_cache_get_ttl() * HZ);
 
 out:
 	kfree(origin_fullpath);
+	ref_walk_free(rw);
 	return rc;
 }
 
@@ -279,7 +272,7 @@ static int update_fs_context_dstaddr(struct smb3_fs_context *ctx)
 	return rc;
 }
 
-int dfs_mount_share(struct cifs_mount_ctx *mnt_ctx, bool *isdfs)
+int dfs_mount_share(struct cifs_mount_ctx *mnt_ctx)
 {
 	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
 	bool nodfs = ctx->nodfs;
@@ -289,7 +282,6 @@ int dfs_mount_share(struct cifs_mount_ctx *mnt_ctx, bool *isdfs)
 	if (rc)
 		return rc;
 
-	*isdfs = false;
 	rc = get_session(mnt_ctx, NULL);
 	if (rc)
 		return rc;
@@ -317,10 +309,15 @@ int dfs_mount_share(struct cifs_mount_ctx *mnt_ctx, bool *isdfs)
 		return rc;
 	}
 
-	*isdfs = true;
-	add_root_smb_session(mnt_ctx);
-	rc = __dfs_mount_share(mnt_ctx);
-	dfs_put_root_smb_sessions(mnt_ctx);
+	if (!ctx->dfs_conn) {
+		ctx->dfs_conn = true;
+		cifs_mount_put_conns(mnt_ctx);
+		rc = get_session(mnt_ctx, NULL);
+	}
+	if (!rc) {
+		set_root_smb_session(mnt_ctx);
+		rc = __dfs_mount_share(mnt_ctx);
+	}
 	return rc;
 }