svn commit: r237351 - stable/9/sys/kern

[Kirk McKusick]

Author: mckusick
Date: Thu Jun 21 03:58:10 2012
New Revision: 237351
URL: http://svn.freebsd.org/changeset/base/237351

Log:
  MFC of 236825
  
  When synchronously syncing a device (MNT_WAIT), wait for buffers
  to become available. Otherwise we may excessively spin and fail
  with ``fsync: giving up on dirty''.
  
  Reviewed by: kib
  Tested by:   Peter Holm

Modified:
  stable/9/sys/kern/vfs_default.c
Directory Properties:
  stable/9/sys/   (props changed)
  stable/9/sys/amd64/include/xen/   (props changed)
  stable/9/sys/boot/   (props changed)
  stable/9/sys/boot/i386/efi/   (props changed)
  stable/9/sys/boot/ia64/efi/   (props changed)
  stable/9/sys/boot/ia64/ski/   (props changed)
  stable/9/sys/boot/powerpc/boot1.chrp/   (props changed)
  stable/9/sys/boot/powerpc/ofw/   (props changed)
  stable/9/sys/cddl/contrib/opensolaris/   (props changed)
  stable/9/sys/conf/   (props changed)
  stable/9/sys/contrib/dev/acpica/   (props changed)
  stable/9/sys/contrib/octeon-sdk/   (props changed)
  stable/9/sys/contrib/pf/   (props changed)
  stable/9/sys/contrib/x86emu/   (props changed)
  stable/9/sys/dev/   (props changed)
  stable/9/sys/dev/e1000/   (props changed)
  stable/9/sys/dev/isp/   (props changed)
  stable/9/sys/dev/ixgbe/   (props changed)
  stable/9/sys/fs/   (props changed)
  stable/9/sys/fs/ntfs/   (props changed)
  stable/9/sys/modules/   (props changed)

Modified: stable/9/sys/kern/vfs_default.c
==============================================================================
--- stable/9/sys/kern/vfs_default.c	Thu Jun 21 03:10:48 2012	(r237350)
+++ stable/9/sys/kern/vfs_default.c	Thu Jun 21 03:58:10 2012	(r237351)
@@ -646,8 +646,17 @@ loop2:
 		if ((bp->b_vflags & BV_SCANNED) != 0)
 			continue;
 		bp->b_vflags |= BV_SCANNED;
-		if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT, NULL))
-			continue;
+		if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT, NULL)) {
+			if (ap->a_waitfor != MNT_WAIT)
+				continue;
+			if (BUF_LOCK(bp,
+			    LK_EXCLUSIVE | LK_INTERLOCK | LK_SLEEPFAIL,
+			    BO_MTX(bo)) != 0) {
+				BO_LOCK(bo);
+				goto loop1;
+			}
+			BO_LOCK(bo);
+		}
 		BO_UNLOCK(bo);
 		KASSERT(bp->b_bufobj == bo,
 		    ("bp %p wrong b_bufobj %p should be %p",