svn commit: r335191 - stable/11/sys/kern

[Mark Johnston]

Author: markj
Date: Fri Jun 15 08:59:24 2018
New Revision: 335191
URL: https://svnweb.freebsd.org/changeset/base/335191

Log:
  MFC r334506:
  Avoid completing I/O when dumping core after a panic.

Modified:
  stable/11/sys/kern/vfs_bio.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/sys/kern/vfs_bio.c
==============================================================================
--- stable/11/sys/kern/vfs_bio.c	Fri Jun 15 08:36:21 2018	(r335190)
+++ stable/11/sys/kern/vfs_bio.c	Fri Jun 15 08:59:24 2018	(r335191)
@@ -3942,6 +3942,8 @@ allocbuf(struct buf *bp, int size)
 
 extern int inflight_transient_maps;
 
+static struct bio_queue nondump_bios;
+
 void
 biodone(struct bio *bp)
 {
@@ -3949,6 +3951,17 @@ biodone(struct bio *bp)
 	void (*done)(struct bio *);
 	vm_offset_t start, end;
 
+
+	/*
+	 * Avoid completing I/O when dumping after a panic since that may
+	 * result in a deadlock in the filesystem or pager code.  Note that
+	 * this doesn't affect dumps that were started manually since we aim
+	 * to keep the system usable after it has been resumed.
+	 */
+	if (__predict_false(dumping && SCHEDULER_STOPPED())) {
+		TAILQ_INSERT_HEAD(&nondump_bios, bp, bio_queue);
+		return;
+	}
 	if ((bp->bio_flags & BIO_TRANSIENT_MAPPING) != 0) {
 		bp->bio_flags &= ~BIO_TRANSIENT_MAPPING;
 		bp->bio_flags |= BIO_UNMAPPED;