xfs: don't validate error tags in the I/O path

We can trust XFS developers enough to not pass random stuff to
XFS_ERROR_TEST/DELAY.  Open code the validity check in xfs_errortag_add,
which is the only place that receives unvalidated error tag values from
user space, and drop the now pointless xfs_errortag_enabled helper.

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

Author: Christoph Hellwig

fs/xfs/libxfs/xfs_errortag.h

@@ -53,7 +53,7 @@
  * Drop-writes support removed because write error handling cannot trash
  * pre-existing delalloc extents in any useful way anymore. We retain the
  * definition so that we can reject it as an invalid value in
- * xfs_errortag_valid().
+ * xfs_errortag_add().
  */
 #define XFS_ERRTAG_DROP_WRITES				28
 #define XFS_ERRTAG_LOG_BAD_CRC				29

fs/xfs/xfs_error.c

@@ -125,30 +125,6 @@ xfs_errortag_del(
 	xfs_sysfs_del(&mp->m_errortag_kobj);
 }
 
-static bool
-xfs_errortag_valid(
-	unsigned int		error_tag)
-{
-	if (error_tag >= XFS_ERRTAG_MAX)
-		return false;
-
-	/* Error out removed injection types */
-	if (error_tag == XFS_ERRTAG_DROP_WRITES)
-		return false;
-	return true;
-}
-
-bool
-xfs_errortag_enabled(
-	struct xfs_mount	*mp,
-	unsigned int		tag)
-{
-	if (!xfs_errortag_valid(tag))
-		return false;
-
-	return mp->m_errortag[tag] != 0;
-}
-
 bool
 xfs_errortag_test(
 	struct xfs_mount	*mp,
@@ -158,9 +134,6 @@ xfs_errortag_test(
 {
 	unsigned int		randfactor;
 
-	if (!xfs_errortag_valid(error_tag))
-		return false;
-
 	randfactor = mp->m_errortag[error_tag];
 	if (!randfactor || get_random_u32_below(randfactor))
 		return false;
@@ -178,8 +151,17 @@ xfs_errortag_add(
 {
 	BUILD_BUG_ON(ARRAY_SIZE(xfs_errortag_random_default) != XFS_ERRTAG_MAX);
 
-	if (!xfs_errortag_valid(error_tag))
+	if (error_tag >= XFS_ERRTAG_MAX)
+		return -EINVAL;
+
+	/* Error out removed injection types */
+	switch (error_tag) {
+	case XFS_ERRTAG_DROP_WRITES:
 		return -EINVAL;
+	default:
+		break;
+	}
+
 	mp->m_errortag[error_tag] = xfs_errortag_random_default[error_tag];
 	return 0;
 }

fs/xfs/xfs_error.h

@@ -44,7 +44,7 @@ bool xfs_errortag_enabled(struct xfs_mount *mp, unsigned int tag);
 #define XFS_ERRORTAG_DELAY(mp, tag)		\
 	do { \
 		might_sleep(); \
-		if (!xfs_errortag_enabled((mp), (tag))) \
+		if (!mp->m_errortag[tag]) \
 			break; \
 		xfs_warn_ratelimited((mp), \
 "Injecting %ums delay at file %s, line %d, on filesystem \"%s\"", \