Hi,
I have been investigating a very intermittent issue we have with xenstore
access hanging. Typically it seems to happen when all domains are stopped
prior to a system reboot. xenstore is running in a stubdom and using the
hypervisor debug keys indicates the domain is still there.
I have come across some old list threads which suggested access via
/proc/xen/xenbus could cause problems but it seems patches went in to the
kernel for 4.10. However to eliminate this entirely as a possibility
I came up with this kernel patch to hide deprecated entries in xenfs.
I found this old thread for a similar change where the entries were made
conditional on kernel config options instead of a module parameter but
this was never merged.
https://lkml.org/lkml/2015/11/30/761
If this would be a useful feature I would welcome feedback.
Thanks,
James
diff --git a/drivers/xen/xenfs/super.c b/drivers/xen/xenfs/super.c
index d7d64235010d..d02c451f6a4d 100644
--- a/drivers/xen/xenfs/super.c
+++ b/drivers/xen/xenfs/super.c
@@ -3,6 +3,11 @@
* xenfs.c - a filesystem for passing info between the a domain and
* the hypervisor.
*
+ * 2022-02-12 James Dingwall Introduce hide_deprecated module parameter to
+ * mask:
+ * - xenbus (deprecated in xen 4.6.0)
+ * - privcmd (deprecated in xen 4.7.0)
+ *
* 2008-10-07 Alex Zeffertt Replaced /proc/xen/xenbus with xenfs filesystem
* and /proc/xen compatibility mount point.
* Turned xenfs into a loadable module.
@@ -28,6 +33,13 @@
MODULE_DESCRIPTION("Xen filesystem");
MODULE_LICENSE("GPL");
+static bool __read_mostly hide_deprecated = 0;
+module_param(hide_deprecated, bool, 0444);
+MODULE_PARM_DESC(hide_deprecated,
+ "Allow deprecated files to be hidden in xenfs.\n"\
+ " 0 - (default) show deprecated xenfs files."\
+ " 1 - hide deprecated xenfs files [xenbus, privcmd].\n");
+
static ssize_t capabilities_read(struct file *file, char __user *buf,
size_t size, loff_t *off)
{
@@ -69,8 +81,32 @@ static int xenfs_fill_super(struct super_block *sb, struct fs_context *fc)
xen_initial_domain() ? xenfs_init_files : xenfs_files);
}
+static int xenfs_fill_super_hide_deprecated(struct super_block *sb, struct fs_context *fc)
+{
+ static const struct tree_descr xenfs_files[] = {
+ [2] = { "capabilities", &capabilities_file_ops, S_IRUGO },
+ {""},
+ };
+
+ static const struct tree_descr xenfs_init_files[] = {
+ [2] = { "capabilities", &capabilities_file_ops, S_IRUGO },
+ { "xsd_kva", &xsd_kva_file_ops, S_IRUSR|S_IWUSR},
+ { "xsd_port", &xsd_port_file_ops, S_IRUSR|S_IWUSR},
+#ifdef CONFIG_XEN_SYMS
+ { "xensyms", &xensyms_ops, S_IRUSR},
+#endif
+ {""},
+ };
+
+ return simple_fill_super(sb, XENFS_SUPER_MAGIC,
+ xen_initial_domain() ? xenfs_init_files : xenfs_files);
+}
+
static int xenfs_get_tree(struct fs_context *fc)
{
+ if(hide_deprecated)
+ return get_tree_single(fc, xenfs_fill_super_hide_deprecated);
+
return get_tree_single(fc, xenfs_fill_super);
}
