[PATCH v2 2/8] smb: client: sync tcon-level options on remount

[rajasimandalos@gmail.com]

From: Rajasi Mandal <rajasimandal@microsoft.com>

Several mount options are stored on each cifs_tcon at mount time but
smb3_reconfigure() only updates cifs_sb->ctx. A remount that changes
any of these options silently has no effect because the runtime code
reads from the tcon fields, not from the superblock context.

The affected options and their tcon fields are:
  retry           -> tcon->retry
  max_cached_dirs -> tcon->max_cached_dirs

Add smb3_sync_tcon_opts() which walks the tlink_tree under
tlink_tree_lock and propagates these values from ctx to every tcon
under tc_lock. Call it from smb3_reconfigure() after the context has
been updated.

Signed-off-by: Rajasi Mandal <rajasimandal@microsoft.com>
---
 fs/smb/client/fs_context.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
index d90430e7a648..20c17f7cbbf8 100644
--- a/fs/smb/client/fs_context.c
+++ b/fs/smb/client/fs_context.c
@@ -1264,6 +1264,38 @@ static void smb3_sync_ses_chan_max(struct cifs_ses *ses, unsigned int max_channe
 	spin_unlock(&ses->chan_lock);
 }
 
+/*
+ * Synchronize tcon options that are derived from ctx across all tcons
+ * associated with this superblock.  These fields are consulted at runtime
+ * (reconnect, I/O, unlink/rmdir) so remount needs to update the live
+ * tcons in addition to cifs_sb->ctx.
+ */
+static void smb3_sync_tcon_opts(struct cifs_sb_info *cifs_sb,
+				struct smb3_fs_context *ctx)
+{
+	struct tcon_link *tlink;
+	struct cifs_tcon *tcon;
+	struct rb_node *node;
+
+	spin_lock(&cifs_sb->tlink_tree_lock);
+	for (node = rb_first(&cifs_sb->tlink_tree); node; node = rb_next(node)) {
+		tlink = rb_entry(node, struct tcon_link, tl_rbnode);
+		tcon = tlink_tcon(tlink);
+		if (IS_ERR(tcon))
+			continue;
+
+		spin_lock(&tcon->tc_lock);
+		tcon->retry = ctx->retry;
+		/*
+		 * Note: this updates the limit for new cached dir opens
+		 * but does not resize or evict existing cached dirents.
+		 */
+		tcon->max_cached_dirs = ctx->max_cached_dirs;
+		spin_unlock(&tcon->tc_lock);
+	}
+	spin_unlock(&cifs_sb->tlink_tree_lock);
+}
+
 static int smb3_reconfigure(struct fs_context *fc)
 {
 	struct smb3_fs_context *ctx = smb3_fc2context(fc);
@@ -1397,6 +1429,8 @@ static int smb3_reconfigure(struct fs_context *fc)
 	if (!rc)
 		rc = dfs_cache_remount_fs(cifs_sb);
 #endif
+	if (!rc)
+		smb3_sync_tcon_opts(cifs_sb, cifs_sb->ctx);
 
 	return rc;
 }
-- 
2.43.0