From d79b4cb4753523aa7f2394b74deffe49e0f0eff4 Mon Sep 17 00:00:00 2001
From: tegge <tegge@FreeBSD.org>
Date: Sat, 6 May 2006 20:51:31 +0000
Subject: ffs_syncvnode() might skip some of the blocks due to them being
 locked, assuming them to be inflight write buffers.  This is not always the
 case. bufdaemon might hold the buffer lock and give up writing the buffer due
 to it having dependencies, the file system being suspended or the vnode lock
 being held by another thread.  When bufdaemon decides to write the buffer
 there is still a window before bufobj_wref() has been called, allowing other
 threads to believe that the vnode has no dirty buffers or inflight writes.

Try harder to flush first block of new subdirectory to get rid of MKDIR_BODY
dependency.
---
 sys/ufs/ffs/ffs_softdep.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

(limited to 'sys/ufs/ffs')

diff --git a/sys/ufs/ffs/ffs_softdep.c b/sys/ufs/ffs/ffs_softdep.c
index 4771460..959fe6a 100644
--- a/sys/ufs/ffs/ffs_softdep.c
+++ b/sys/ufs/ffs/ffs_softdep.c
@@ -5501,6 +5501,7 @@ flush_pagedep_deps(pvp, mp, diraddhdp)
 	int error = 0;
 	struct buf *bp;
 	ino_t inum;
+	struct worklist *wk;
 
 	ump = VFSTOUFS(mp);
 	while ((dap = LIST_FIRST(diraddhdp)) != NULL) {
@@ -5545,8 +5546,53 @@ flush_pagedep_deps(pvp, mp, diraddhdp)
 			}
 			VI_LOCK(vp);
 			drain_output(vp);
+			/*
+			 * If first block is still dirty with a D_MKDIR
+			 * dependency then it needs to be written now.
+			 */
+			for (;;) {
+				error = 0;
+				bp = gbincore(&vp->v_bufobj, 0);
+				if (bp == NULL)
+					break;	/* First block not present */
+				error = BUF_LOCK(bp,
+						 LK_EXCLUSIVE |
+						 LK_SLEEPFAIL |
+						 LK_INTERLOCK,
+						 VI_MTX(vp));
+				VI_LOCK(vp);
+				if (error == ENOLCK)
+					continue;	/* Slept, retry */
+				if (error != 0)
+					break;		/* Failed */
+				if ((bp->b_flags & B_DELWRI) == 0) {
+					BUF_UNLOCK(bp);
+					break;	/* Buffer not dirty */
+				}
+				for (wk = LIST_FIRST(&bp->b_dep);
+				     wk != NULL;
+				     wk = LIST_NEXT(wk, wk_list))
+					if (wk->wk_type == D_MKDIR)
+						break;
+				if (wk == NULL)
+					BUF_UNLOCK(bp);	/* Dependency gone */
+				else {
+					/*
+					 * D_MKDIR dependency remains,
+					 * must write buffer to stable
+					 * storage.
+					 */
+					VI_UNLOCK(vp);
+					bremfree(bp);
+					error = bwrite(bp);
+					VI_LOCK(vp);
+				}
+				break;
+			}
 			VI_UNLOCK(vp);
 			vput(vp);
+			if (error != 0)
+				break;	/* Flushing of first block failed */
 			ACQUIRE_LOCK(&lk);
 			/*
 			 * If that cleared dependencies, go on to next.
-- 
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