From 62a2c422ea86449cbba170c4adee0b82e003f971 Mon Sep 17 00:00:00 2001
From: Matthew Dillon <dillon@apollo.backplane.com>
Date: Tue, 22 Aug 2017 16:43:11 -0700
Subject: [PATCH] hammer2 - limit show command output when crc error

* When a CRC error check fails on a recursive chain during the debugging
  'show' command output, limit recursion down that chain to one level.
  This allows the potentially corrupted data record to be dissected but
  does not attempt further indirection through it.
---
 sbin/hammer2/cmd_debug.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/sbin/hammer2/cmd_debug.c b/sbin/hammer2/cmd_debug.c
index 637195c38c..3fccc83037 100644
--- a/sbin/hammer2/cmd_debug.c
+++ b/sbin/hammer2/cmd_debug.c
@@ -373,7 +373,7 @@ cmd_debugspan(const char *hostname)
  ************************************************************************/
 
 static void show_bref(int fd, int tab, int bi, hammer2_blockref_t *bref,
-			int dofreemap);
+			int dofreemap, int norecurse);
 static void tabprintf(int tab, const char *ctl, ...);
 
 int
@@ -412,11 +412,11 @@ cmd_show(const char *devpath, int dofreemap)
 				best = broot;
 			}
 			if (VerboseOpt >= 3)
-				show_bref(fd, 0, i, &broot, dofreemap);
+				show_bref(fd, 0, i, &broot, dofreemap, 0);
 		}
 	}
 	if (VerboseOpt < 3)
-		show_bref(fd, 0, best_i, &best, dofreemap);
+		show_bref(fd, 0, best_i, &best, dofreemap, 0);
 	close(fd);
 
 	return 0;
@@ -424,7 +424,8 @@ cmd_show(const char *devpath, int dofreemap)
 
 extern uint32_t iscsi_crc32(const void *buf, size_t size);
 static void
-show_bref(int fd, int tab, int bi, hammer2_blockref_t *bref, int dofreemap)
+show_bref(int fd, int tab, int bi, hammer2_blockref_t *bref, int dofreemap,
+	  int norecurse)
 {
 	hammer2_media_data_t media;
 	hammer2_blockref_t *bscan;
@@ -433,6 +434,7 @@ show_bref(int fd, int tab, int bi, hammer2_blockref_t *bref, int dofreemap)
 	int didnl;
 	int namelen;
 	int obrace = 1;
+	int failed;
 	size_t bytes;
 	const char *type_str;
 	char *str = NULL;
@@ -517,6 +519,7 @@ show_bref(int fd, int tab, int bi, hammer2_blockref_t *bref, int dofreemap)
 	bcount = 0;
 	didnl = 1;
 	namelen = 0;
+	failed = 0;
 
 	/*
 	 * Check data integrity in verbose mode, otherwise we are just doing
@@ -543,6 +546,7 @@ show_bref(int fd, int tab, int bi, hammer2_blockref_t *bref, int dofreemap)
 				       bref->methods,
 				       bref->check.iscsi32.value,
 				       cv);
+				failed = 1;
 			} else {
 				printf("(meth %02x, iscsi32=%08x) ",
 				       bref->methods, cv);
@@ -555,6 +559,7 @@ show_bref(int fd, int tab, int bi, hammer2_blockref_t *bref, int dofreemap)
 				       bref->methods,
 				       bref->check.xxhash64.value,
 				       cv64);
+				failed = 1;
 			} else {
 				printf("(meth %02x, xxh=%016jx) ",
 				       bref->methods, cv64);
@@ -570,6 +575,7 @@ show_bref(int fd, int tab, int bi, hammer2_blockref_t *bref, int dofreemap)
 					bref->methods,
 					bref->check.freemap.icrc32,
 					cv);
+				failed = 1;
 			} else {
 				printf("(meth %02x, fcrc=%08x) ",
 					bref->methods, cv);
@@ -758,13 +764,20 @@ show_bref(int fd, int tab, int bi, hammer2_blockref_t *bref, int dofreemap)
 	}
 	if (str)
 		free(str);
-	for (i = 0; i < bcount; ++i) {
+
+	/*
+	 * Recurse if norecurse == 0.  If the CRC failed, pass norecurse = 1.
+	 * That is, if an indirect or inode fails we still try to list its
+	 * direct children to help with debugging, but go no further than
+	 * that because they are probably garbage.
+	 */
+	for (i = 0; norecurse == 0 && i < bcount; ++i) {
 		if (bscan[i].type != HAMMER2_BREF_TYPE_EMPTY) {
 			if (didnl == 0) {
 				printf("\n");
 				didnl = 1;
 			}
-			show_bref(fd, tab, i, &bscan[i], dofreemap);
+			show_bref(fd, tab, i, &bscan[i], dofreemap, failed);
 		}
 	}
 	tab -= SHOW_TAB;
-- 
2.41.0