From: Nicolas Thery <nth@dragonflybsd.org>
Date: Mon, 28 Jan 2008 07:19:06 +0000 (+0000)
Subject: Fix spurious "softdep_deallocate_dependencies: dangling deps" panic occuring
X-Git-Tag: v2.0.1~1250
X-Git-Url: https://gitweb.dragonflybsd.org/dragonfly.git/commitdiff_plain/389ee6be5ec057aa7edea264f883337feda155d3

Fix spurious "softdep_deallocate_dependencies: dangling deps" panic occuring
on low memory condition.

Add assertion to catch similar bugs automagically.

Reported-by: Peter Avalos <pavalos@theshell.com>

Reviewed-by: Matthew Dillon <dillon@backplane.com>
---

diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
index f2d2186893..d18344394f 100644
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -12,7 +12,7 @@
  *		John S. Dyson.
  *
  * $FreeBSD: src/sys/kern/vfs_bio.c,v 1.242.2.20 2003/05/28 18:38:10 alc Exp $
- * $DragonFly: src/sys/kern/vfs_bio.c,v 1.96 2008/01/10 07:34:01 dillon Exp $
+ * $DragonFly: src/sys/kern/vfs_bio.c,v 1.97 2008/01/28 07:19:06 nth Exp $
  */
 
 /*
@@ -1085,7 +1085,8 @@ brelse(struct buf *bp)
 	if (bp->b_flags & (B_DELWRI | B_LOCKED)) {
 		bp->b_flags &= ~B_RELBUF;
 	} else if (vm_page_count_severe()) {
-		buf_deallocate(bp);
+		if (LIST_FIRST(&bp->b_dep) != NULL)
+			buf_deallocate(bp);
 		if (bp->b_flags & (B_DELWRI | B_LOCKED))
 			bp->b_flags &= ~B_RELBUF;
 		else
diff --git a/sys/sys/buf2.h b/sys/sys/buf2.h
index b91f04b698..ed2a8502f1 100644
--- a/sys/sys/buf2.h
+++ b/sys/sys/buf2.h
@@ -37,7 +37,7 @@
  *
  *	@(#)buf.h	8.9 (Berkeley) 3/30/95
  * $FreeBSD: src/sys/sys/buf.h,v 1.88.2.10 2003/01/25 19:02:23 dillon Exp $
- * $DragonFly: src/sys/sys/buf2.h,v 1.20 2007/11/07 00:46:38 dillon Exp $
+ * $DragonFly: src/sys/sys/buf2.h,v 1.21 2008/01/28 07:19:06 nth Exp $
  */
 
 #ifndef _SYS_BUF2_H_
@@ -195,11 +195,15 @@ buf_dep_init(struct buf *bp)
 	LIST_INIT(&bp->b_dep);
 }
 
+/*
+ * Precondition: the buffer has some dependencies.
+ */
 static __inline void
 buf_deallocate(struct buf *bp)
 {
 	struct bio_ops *ops = bp->b_ops;
 
+	KKASSERT(! LIST_EMPTY(&bp->b_dep));
 	if (ops)
 		ops->io_deallocate(bp);
 }