2 files changed, 25 insertions, 8 deletions

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 24643169e632..b612ce4520ae 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -3407,6 +3407,17 @@ xlog_verify_dest_ptr(
                 xfs_emerg(log->l_mp, "%s: invalid ptr", __func__);
 }
 
+/*
+ * Check to make sure the grant write head didn't just over lap the tail.  If
+ * the cycles are the same, we can't be overlapping.  Otherwise, make sure that
+ * the cycles differ by exactly one and check the byte count.
+ *
+ * This check is run unlocked, so can give false positives. Rather than assert
+ * on failures, use a warn-once flag and a panic tag to allow the admin to
+ * determine if they want to panic the machine when such an error occurs. For
+ * debug kernels this will have the same effect as using an assert but, unlinke
+ * an assert, it can be turned off at runtime.
+ */
 STATIC void
 xlog_verify_grant_tail(
         struct log      *log)
@@ -3414,17 +3425,22 @@ xlog_verify_grant_tail(
         int             tail_cycle, tail_blocks;
         int             cycle, space;
 
-        /*
-         * Check to make sure the grant write head didn't just over lap the
-         * tail.  If the cycles are the same, we can't be overlapping.
-         * Otherwise, make sure that the cycles differ by exactly one and
-         * check the byte count.
-         */
         xlog_crack_grant_head(&log->l_grant_write_head, &cycle, &space);
         xlog_crack_atomic_lsn(&log->l_tail_lsn, &tail_cycle, &tail_blocks);
         if (tail_cycle != cycle) {
-                ASSERT(cycle - 1 == tail_cycle);
-                ASSERT(space <= BBTOB(tail_blocks));
+                if (cycle - 1 != tail_cycle &&
+                    !(log->l_flags & XLOG_TAIL_WARN)) {
+                        xfs_alert_tag(log->l_mp, XFS_PTAG_LOGRES,
+                                "%s: cycle - 1 != tail_cycle", __func__);
+                        log->l_flags |= XLOG_TAIL_WARN;
+                }
+
+                if (space > BBTOB(tail_blocks) &&
+                    !(log->l_flags & XLOG_TAIL_WARN)) {
+                        xfs_alert_tag(log->l_mp, XFS_PTAG_LOGRES,
+                                "%s: space > BBTOB(tail_blocks)", __func__);
+                        log->l_flags |= XLOG_TAIL_WARN;
+                }
         }
 }
 
diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index 15dbf1f9c2be..bc988d4ef958 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -144,6 +144,7 @@ static inline uint xlog_get_client_id(__be32 i)
 #define XLOG_RECOVERY_NEEDED    0x4     /* log was recovered */
 #define XLOG_IO_ERROR           0x8     /* log hit an I/O error, and being
                                            shutdown */
+#define XLOG_TAIL_WARN          0x10    /* log tail verify warning issued */
 
 #ifdef __KERNEL__
 /*