xfs: allow setting errortags at mount time

Add an errortag mount option that enables an errortag with the default
injection frequency.  This allows injecting errors into the mount
process instead of just on live file systems, and thus test mount
error handling.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hans Holmberg <hans.holmberg@wdc.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

Author: Christoph Hellwig

Documentation/admin-guide/xfs.rst

@@ -215,6 +215,14 @@ When mounting an XFS filesystem, the following options are accepted.
 	inconsistent namespace presentation during or after a
 	failover event.
 
+  errortag=tagname
+	When specified, enables the error inject tag named "tagname" with the
+	default frequency.  Can be specified multiple times to enable multiple
+	errortags.  Specifying this option on remount will reset the error tag
+	to the default value if it was set to any other value before.
+	This option is only supported when CONFIG_XFS_DEBUG is enabled, and
+	will not be reflected in /proc/self/mounts.
+
 Deprecation of V4 Format
 ========================
 

fs/xfs/xfs_error.c

@@ -22,6 +22,12 @@
 static const unsigned int xfs_errortag_random_default[] = { XFS_ERRTAGS };
 #undef XFS_ERRTAG
 
+#define XFS_ERRTAG(_tag, _name, _default) \
+        [XFS_ERRTAG_##_tag]	=  __stringify(_name),
+#include "xfs_errortag.h"
+static const char *xfs_errortag_names[] = { XFS_ERRTAGS };
+#undef XFS_ERRTAG
+
 struct xfs_errortag_attr {
 	struct attribute	attr;
 	unsigned int		tag;
@@ -189,6 +195,36 @@ xfs_errortag_add(
 	return 0;
 }
 
+int
+xfs_errortag_add_name(
+	struct xfs_mount	*mp,
+	const char		*tag_name)
+{
+	unsigned int		i;
+
+	for (i = 0; i < XFS_ERRTAG_MAX; i++) {
+		if (xfs_errortag_names[i] &&
+		    !strcmp(xfs_errortag_names[i], tag_name))
+			return xfs_errortag_add(mp, i);
+	}
+
+	return -EINVAL;
+}
+
+void
+xfs_errortag_copy(
+	struct xfs_mount	*dst_mp,
+	struct xfs_mount	*src_mp)
+{
+	unsigned int		val, i;
+
+	for (i = 0; i < XFS_ERRTAG_MAX; i++) {
+		val = READ_ONCE(src_mp->m_errortag[i]);
+		if (val)
+			WRITE_ONCE(dst_mp->m_errortag[i], val);
+	}
+}
+
 int
 xfs_errortag_clearall(
 	struct xfs_mount	*mp)

fs/xfs/xfs_error.h

@@ -45,13 +45,17 @@ void xfs_errortag_delay(struct xfs_mount *mp, const char *file, int line,
 #define XFS_ERRORTAG_DELAY(mp, tag)		\
 	xfs_errortag_delay((mp), __FILE__, __LINE__, (tag))
 int xfs_errortag_add(struct xfs_mount *mp, unsigned int error_tag);
+int xfs_errortag_add_name(struct xfs_mount *mp, const char *tag_name);
+void xfs_errortag_copy(struct xfs_mount *dst_mp, struct xfs_mount *src_mp);
 int xfs_errortag_clearall(struct xfs_mount *mp);
 #else
 #define xfs_errortag_init(mp)			(0)
 #define xfs_errortag_del(mp)
 #define XFS_TEST_ERROR(mp, tag)			(false)
 #define XFS_ERRORTAG_DELAY(mp, tag)		((void)0)
 #define xfs_errortag_add(mp, tag)		(-ENOSYS)
+#define xfs_errortag_copy(dst_mp, src_mp)	((void)0)
+#define xfs_errortag_add_name(mp, tag_name)	(-ENOSYS)
 #define xfs_errortag_clearall(mp)		(-ENOSYS)
 #endif /* DEBUG */
 

fs/xfs/xfs_super.c

@@ -40,6 +40,7 @@
 #include "xfs_defer.h"
 #include "xfs_attr_item.h"
 #include "xfs_xattr.h"
+#include "xfs_error.h"
 #include "xfs_errortag.h"
 #include "xfs_iunlink_item.h"
 #include "xfs_dahash_test.h"
@@ -114,7 +115,7 @@ enum {
 	Opt_prjquota, Opt_uquota, Opt_gquota, Opt_pquota,
 	Opt_uqnoenforce, Opt_gqnoenforce, Opt_pqnoenforce, Opt_qnoenforce,
 	Opt_discard, Opt_nodiscard, Opt_dax, Opt_dax_enum, Opt_max_open_zones,
-	Opt_lifetime, Opt_nolifetime, Opt_max_atomic_write,
+	Opt_lifetime, Opt_nolifetime, Opt_max_atomic_write, Opt_errortag,
 };
 
 #define fsparam_dead(NAME) \
@@ -173,6 +174,7 @@ static const struct fs_parameter_spec xfs_fs_parameters[] = {
 	fsparam_flag("lifetime",	Opt_lifetime),
 	fsparam_flag("nolifetime",	Opt_nolifetime),
 	fsparam_string("max_atomic_write",	Opt_max_atomic_write),
+	fsparam_string("errortag",	Opt_errortag),
 	{}
 };
 
@@ -1593,6 +1595,8 @@ xfs_fs_parse_param(
 			return -EINVAL;
 		}
 		return 0;
+	case Opt_errortag:
+		return xfs_errortag_add_name(parsing_mp, param->string);
 	default:
 		xfs_warn(parsing_mp, "unknown mount option [%s].", param->key);
 		return -EINVAL;
@@ -2184,6 +2188,8 @@ xfs_fs_reconfigure(
 	if (error)
 		return error;
 
+	xfs_errortag_copy(mp, new_mp);
+
 	/* Validate new max_atomic_write option before making other changes */
 	if (mp->m_awu_max_bytes != new_mp->m_awu_max_bytes) {
 		error = xfs_set_max_atomic_write_opt(mp,