- 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, 0 deletions

diff --git a/sys/nfsclient/nfs_bio.c b/sys/nfsclient/nfs_bio.c
index 1ae3157..56e2cb6 100644
--- a/sys/nfsclient/nfs_bio.c
+++ b/sys/nfsclient/nfs_bio.c
@@ -1241,6 +1241,8 @@ again:
 				bp->b_wcred = crhold(cred);
 		}
 
+		if (bp->b_flags & B_REMFREE)
+			bremfreef(bp);
 		BUF_KERNPROC(bp);
 		TAILQ_INSERT_TAIL(&nmp->nm_bufq, bp, b_freelist);
 		nmp->nm_bufqlen++;