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Date:      Sun, 4 May 2014 14:05:15 +0000 (UTC)
From:      Steven Hartland <smh@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r265321 - in head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs: . sys
Message-ID:  <201405041405.s44E5FU9006213@svn.freebsd.org>
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Author: smh
Date: Sun May  4 14:05:14 2014
New Revision: 265321
URL: http://svnweb.freebsd.org/changeset/base/265321

Log:
  Use a zio flag to prevent recursion of vdev_queue_io_done which can
  cause stack overflow for IO's which return ZIO_PIPELINE_CONTINUE
  from the zio_vdev_io_start stage and hence don't suspend and complete
  in a different thread.
  
  This prevents double fault panic on slow machines running ZFS on
  GELI volumes which return EOPNOTSUPP directly to BIO_DELETE requests.
  
  MFC after:	1 month
  X-MFC-With:	r265152

Modified:
  head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/zio.h
  head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_queue.c

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/zio.h
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/zio.h	Sun May  4 12:32:37 2014	(r265320)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/zio.h	Sun May  4 14:05:14 2014	(r265321)
@@ -196,6 +196,7 @@ enum zio_flag {
 	ZIO_FLAG_NOPWRITE	= 1 << 25,
 	ZIO_FLAG_REEXECUTED	= 1 << 26,
 	ZIO_FLAG_DELEGATED	= 1 << 27,
+	ZIO_FLAG_QUEUE_IO_DONE	= 1 << 28,
 };
 
 #define	ZIO_FLAG_MUSTSUCCEED		0

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_queue.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_queue.c	Sun May  4 12:32:37 2014	(r265320)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_queue.c	Sun May  4 14:05:14 2014	(r265321)
@@ -796,14 +796,25 @@ vdev_queue_io_done(zio_t *zio)
 
 	vq->vq_io_complete_ts = gethrtime();
 
+	if (zio->io_flags & ZIO_FLAG_QUEUE_IO_DONE) {
+		/*
+		 * Executing from a previous vdev_queue_io_done so
+		 * to avoid recursion we just unlock and return.
+		 */
+		mutex_exit(&vq->vq_lock);
+		return;
+	}
+
 	while ((nio = vdev_queue_io_to_issue(vq)) != NULL) {
 		mutex_exit(&vq->vq_lock);
+		nio->io_flags |= ZIO_FLAG_QUEUE_IO_DONE;
 		if (nio->io_done == vdev_queue_agg_io_done) {
 			zio_nowait(nio);
 		} else {
 			zio_vdev_io_reissue(nio);
 			zio_execute(nio);
 		}
+		nio->io_flags &= ~ZIO_FLAG_QUEUE_IO_DONE;
 		mutex_enter(&vq->vq_lock);
 	}

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