- Eliminate the acquisition and release of the bqlock in bremfree() by

   setting the B_REMFREE flag in the buf.  This is done to prevent lock order
   reversals with code that must call bremfree() with a local lock held.
   This also reduces overhead by removing two lock operations per buf for
   fsync() and similar.
 - Check for the B_REMFREE flag in brelse() and bqrelse() after the bqlock
   has been acquired so that we may remove ourself from the free-list.
 - Provide a bremfreef() function to immediately remove a buf from a
   free-list for use only by NFS.  This is done because the nfsclient code
   overloads the b_freelist queue for its own async. io queue.
 - Simplify the numfreebuffers accounting by removing a switch statement
   that executed the same code in every possible case.
 - getnewbuf() can encounter locked bufs on free-lists once Giant is removed.
   Remove a panic associated with this condition and delay asserts that
   inspect the buf until after it is locked.

Reviewed by:	phk
Sponsored by:	Isilon Systems, Inc.

1 files changed, 2 insertions, 1 deletions

diff --git a/sys/ufs/ffs/ffs_vnops.c b/sys/ufs/ffs/ffs_vnops.c
index e903b6d..3716bb0 100644
--- a/sys/ufs/ffs/ffs_vnops.c
+++ b/sys/ufs/ffs/ffs_vnops.c
@@ -208,14 +208,15 @@ loop:
 			continue;
 		if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT, NULL))
 			continue;
+		VI_UNLOCK(vp);
 		if (!wait && LIST_FIRST(&bp->b_dep) != NULL &&
 		    (bp->b_flags & B_DEFERRED) == 0 &&
 		    buf_countdeps(bp, 0)) {
 			bp->b_flags |= B_DEFERRED;
 			BUF_UNLOCK(bp);
+			VI_LOCK(vp);
 			continue;
 		}
-		VI_UNLOCK(vp);
 		if ((bp->b_flags & B_DELWRI) == 0)
 			panic("ffs_fsync: not dirty");
 		/*