Improve the informations reported in case of busy buffers during the shutdown:

- Axe out the SHOW_BUSYBUFS option and uses a tunable for selectively
enable/disable it, which is defaulted for not printing anything (0
value) but can be changed for printing (1 value) and be verbose (2
value)
- Improves the informations outputed: right now, there is no track of
the actual struct buf object or vnode which are referenced by the
shutdown process, but it is printed the related struct bufobj object
which is not really helpful
- Add more verbosity about the state of the struct buf lock and the
vnode informations, with the latter to be activated separately by the
sysctl

Sponsored by:	Sandvine Incorporated
Reviewed by:	emaste, kib
Approved by:	re (ksmith)
MFC after:	10 days

2 files changed, 21 insertions, 9 deletions

diff --git a/sys/kern/kern_shutdown.c b/sys/kern/kern_shutdown.c
index 7621b15..6a8a597 100644
--- a/sys/kern/kern_shutdown.c
+++ b/sys/kern/kern_shutdown.c
@@ -40,7 +40,6 @@ __FBSDID("$FreeBSD$");
 #include "opt_ddb.h"
 #include "opt_kdb.h"
 #include "opt_panic.h"
-#include "opt_show_busybufs.h"
 #include "opt_sched.h"
 #include "opt_watchdog.h"
 
@@ -66,6 +65,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/smp.h>
 #include <sys/sysctl.h>
 #include <sys/sysproto.h>
+#include <sys/vnode.h>
 #ifdef SW_WATCHDOG
 #include <sys/watchdog.h>
 #endif
@@ -123,6 +123,14 @@ TUNABLE_INT("kern.sync_on_panic", &sync_on_panic);
 
 SYSCTL_NODE(_kern, OID_AUTO, shutdown, CTLFLAG_RW, 0, "Shutdown environment");
 
+#ifndef DIAGNOSTIC
+static int show_busybufs;
+#else
+static int show_busybufs = 1;
+#endif
+SYSCTL_INT(_kern_shutdown, OID_AUTO, show_busybufs, CTLFLAG_RW,
+	&show_busybufs, 0, "");
+
 /*
  * Variable panicstr contains argument to first call to panic; used as flag
  * to indicate that the kernel has already called panic.
@@ -389,13 +397,17 @@ kern_reboot(int howto)
 				}
 #endif
 				nbusy++;
-#if defined(SHOW_BUSYBUFS) || defined(DIAGNOSTIC)
-				printf(
-			    "%d: bufobj:%p, flags:%0x, blkno:%ld, lblkno:%ld\n",
-				    nbusy, bp->b_bufobj,
-				    bp->b_flags, (long)bp->b_blkno,
-				    (long)bp->b_lblkno);
-#endif
+				if (show_busybufs > 0) {
+					printf(
+	    "%d: buf:%p, vnode:%p, flags:%0x, blkno:%jd, lblkno:%jd, buflock:",
+					    nbusy, bp, bp->b_vp, bp->b_flags,
+					    (intmax_t)bp->b_blkno,
+					    (intmax_t)bp->b_lblkno);
+					BUF_LOCKPRINTINFO(bp);
+					if (show_busybufs > 1)
+						vn_printf(bp->b_vp,
+						    "vnode content: ");
+				}
 			}
 		}
 		if (nbusy) {
diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
index a6ad81e..7b5b015 100644
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -4020,7 +4020,7 @@ DB_SHOW_COMMAND(buffer, db_show_buffer)
 		db_printf("\n");
 	}
 	db_printf(" ");
-	lockmgr_printinfo(&bp->b_lock);
+	BUF_LOCKPRINTINFO(bp);
 }
 
 DB_SHOW_COMMAND(lockedbufs, lockedbufs)