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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Wed, 13 Mar 2013 10:04:48 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
 svn-src-stable@freebsd.org, svn-src-stable-9@freebsd.org
Subject: svn commit: r248234 - stable/9/sys/kern
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Author: kib
Date: Wed Mar 13 10:04:47 2013
New Revision: 248234
URL: http://svnweb.freebsd.org/changeset/base/248234

Log:
  MFC r247389:
  Make recursive getblk() slightly more useful.

Modified:
  stable/9/sys/kern/vfs_bio.c
Directory Properties:
  stable/9/sys/   (props changed)

Modified: stable/9/sys/kern/vfs_bio.c
==============================================================================
--- stable/9/sys/kern/vfs_bio.c	Wed Mar 13 10:01:05 2013	(r248233)
+++ stable/9/sys/kern/vfs_bio.c	Wed Mar 13 10:04:47 2013	(r248234)
@@ -1252,6 +1252,15 @@ brelse(struct buf *bp)
 	KASSERT(!(bp->b_flags & (B_CLUSTER|B_PAGING)),
 	    ("brelse: inappropriate B_PAGING or B_CLUSTER bp %p", bp));
 
+	if (BUF_LOCKRECURSED(bp)) {
+		/*
+		 * Do not process, in particular, do not handle the
+		 * B_INVAL/B_RELBUF and do not release to free list.
+		 */
+		BUF_UNLOCK(bp);
+		return;
+	}
+
 	if (bp->b_flags & B_MANAGED) {
 		bqrelse(bp);
 		return;
@@ -1428,12 +1437,6 @@ brelse(struct buf *bp)
 			brelvp(bp);
 	}
 			
-	if (BUF_LOCKRECURSED(bp)) {
-		/* do not release to free list */
-		BUF_UNLOCK(bp);
-		return;
-	}
-
 	/* enqueue */
 	mtx_lock(&bqlock);
 	/* Handle delayed bremfree() processing. */
@@ -2683,6 +2686,9 @@ loop:
 		/* We timed out or were interrupted. */
 		else if (error)
 			return (NULL);
+		/* If recursed, assume caller knows the rules. */
+		else if (BUF_LOCKRECURSED(bp))
+			goto end;
 
 		/*
 		 * The buffer is locked.  B_CACHE is cleared if the buffer is 
@@ -2862,6 +2868,7 @@ loop:
 	}
 	CTR4(KTR_BUF, "getblk(%p, %ld, %d) = %p", vp, (long)blkno, size, bp);
 	BUF_ASSERT_HELD(bp);
+end:
 	KASSERT(bp->b_bufobj == bo,
 	    ("bp %p wrong b_bufobj %p should be %p", bp, bp->b_bufobj, bo));
 	return (bp);