From 6742006e9a1611e64b1333cc43565dd8468857a9 Mon Sep 17 00:00:00 2001
From: kib <kib@ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f>
Date: Sat, 11 Jul 2015 19:11:40 +0000
Subject: [PATCH] MFC r284887: Handle errors from background write of the
 cylinder group blocks.

MFC r284927:
Simplify code.

Approved by:	re (gjb)


git-svn-id: svn://svn.freebsd.org/base/stable/10@285402 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
---
 sys/kern/vfs_bio.c       | 22 +++++++++++++++++++++-
 sys/sys/buf.h            |  3 ++-
 sys/ufs/ffs/ffs_vfsops.c | 19 ++++++++++++++++++-
 3 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
index 63f9a3441..f306b5ac7 100644
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -1566,6 +1566,12 @@ brelse(struct buf *bp)
 		return;
 	}
 
+	if ((bp->b_vflags & (BV_BKGRDINPROG | BV_BKGRDERR)) == BV_BKGRDERR) {
+		BO_LOCK(bp->b_bufobj);
+		bp->b_vflags &= ~BV_BKGRDERR;
+		BO_UNLOCK(bp->b_bufobj);
+		bdirty(bp);
+	}
 	if (bp->b_iocmd == BIO_WRITE && (bp->b_ioflags & BIO_ERROR) &&
 	    bp->b_error == EIO && !(bp->b_flags & B_INVAL)) {
 		/*
@@ -1822,7 +1828,11 @@ bqrelse(struct buf *bp)
 	}
 
 	/* buffers with stale but valid contents */
-	if (bp->b_flags & B_DELWRI) {
+	if ((bp->b_flags & B_DELWRI) != 0 || (bp->b_vflags & (BV_BKGRDINPROG |
+	    BV_BKGRDERR)) == BV_BKGRDERR) {
+		BO_LOCK(bp->b_bufobj);
+		bp->b_vflags &= ~BV_BKGRDERR;
+		BO_UNLOCK(bp->b_bufobj);
 		qindex = QUEUE_DIRTY;
 	} else {
 		if ((bp->b_flags & B_DELWRI) == 0 &&
@@ -2341,6 +2351,16 @@ getnewbuf_scan(int maxsize, int defrag, int unmapped, int metadata)
 			continue;
 		}
 
+		/*
+		 * Requeue the background write buffer with error.
+		 */
+		if ((bp->b_vflags & BV_BKGRDERR) != 0) {
+			bremfreel(bp);
+			mtx_unlock(&bqclean);
+			bqrelse(bp);
+			continue;
+		}
+
 		KASSERT(bp->b_qindex == qindex,
 		    ("getnewbuf: inconsistent queue %d bp %p", qindex, bp));
 
diff --git a/sys/sys/buf.h b/sys/sys/buf.h
index 1170be7ac..540d81282 100644
--- a/sys/sys/buf.h
+++ b/sys/sys/buf.h
@@ -248,8 +248,9 @@ struct buf {
 #define	BV_SCANNED	0x00000001	/* VOP_FSYNC funcs mark written bufs */
 #define	BV_BKGRDINPROG	0x00000002	/* Background write in progress */
 #define	BV_BKGRDWAIT	0x00000004	/* Background write waiting */
+#define	BV_BKGRDERR	0x00000008	/* Error from background write */
 
-#define	PRINT_BUF_VFLAGS "\20\3bkgrdwait\2bkgrdinprog\1scanned"
+#define	PRINT_BUF_VFLAGS "\20\4bkgrderr\3bkgrdwait\2bkgrdinprog\1scanned"
 
 #ifdef _KERNEL
 /*
diff --git a/sys/ufs/ffs/ffs_vfsops.c b/sys/ufs/ffs/ffs_vfsops.c
index 53d85bd3f..26c028665 100644
--- a/sys/ufs/ffs/ffs_vfsops.c
+++ b/sys/ufs/ffs/ffs_vfsops.c
@@ -1977,12 +1977,19 @@ ffs_backgroundwritedone(struct buf *bp)
 	BO_LOCK(bufobj);
 	if ((origbp = gbincore(bp->b_bufobj, bp->b_lblkno)) == NULL)
 		panic("backgroundwritedone: lost buffer");
+
+	/*
+	 * We should mark the cylinder group buffer origbp as
+	 * dirty, to not loose the failed write.
+	 */
+	if ((bp->b_ioflags & BIO_ERROR) != 0)
+		origbp->b_vflags |= BV_BKGRDERR;
 	BO_UNLOCK(bufobj);
 	/*
 	 * Process dependencies then return any unfinished ones.
 	 */
 	pbrelvp(bp);
-	if (!LIST_EMPTY(&bp->b_dep))
+	if (!LIST_EMPTY(&bp->b_dep) && (bp->b_ioflags & BIO_ERROR) == 0)
 		buf_complete(bp);
 #ifdef SOFTUPDATES
 	if (!LIST_EMPTY(&bp->b_dep))
@@ -1994,6 +2001,15 @@ ffs_backgroundwritedone(struct buf *bp)
 	 */
 	bp->b_flags |= B_NOCACHE;
 	bp->b_flags &= ~B_CACHE;
+
+	/*
+	 * Prevent brelse() from trying to keep and re-dirtying bp on
+	 * errors. It causes b_bufobj dereference in
+	 * bdirty()/reassignbuf(), and b_bufobj was cleared in
+	 * pbrelvp() above.
+	 */
+	if ((bp->b_ioflags & BIO_ERROR) != 0)
+		bp->b_flags |= B_INVAL;
 	bufdone(bp);
 	BO_LOCK(bufobj);
 	/*
@@ -2055,6 +2071,7 @@ ffs_bufwrite(struct buf *bp)
 		if (bp->b_vflags & BV_BKGRDINPROG)
 			panic("bufwrite: still writing");
 	}
+	bp->b_vflags &= ~BV_BKGRDERR;
 	BO_UNLOCK(bp->b_bufobj);
 
 	/*
-- 
2.45.0