From: Brad Lewis <brad.lewis@delphix.com>
Date: Thu, 15 Mar 2018 19:47:26 +0000 (-0600)
Subject: OpenZFS 9677 - panic from zio_write_gang_block()
X-Git-Tag: zfs-0.8.0-rc2~78
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=c955398b527fd0996cc03b55ba26a4647bd826cd;p=zfs

OpenZFS 9677 - panic from zio_write_gang_block()

Panic from zio_write_gang_block() when creating dump device
on fragmented rpool.

Authored by: Brad Lewis <brad.lewis@delphix.com>
Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Prashanth Sreenivasa <pks@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Ported-by: Behlendorf <behlendorf1@llnl.gov>

OpenZFS-issue: https://illumos.org/issues/9677
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7341a7d
Closes #7975
---

diff --git a/module/zfs/zio.c b/module/zfs/zio.c
index d3208a1e7..e8c2ca89a 100644
--- a/module/zfs/zio.c
+++ b/module/zfs/zio.c
@@ -2603,7 +2603,13 @@ zio_write_gang_member_ready(zio_t *zio)
 static void
 zio_write_gang_done(zio_t *zio)
 {
-	abd_put(zio->io_abd);
+	/*
+	 * The io_abd field will be NULL for a zio with no data.  The io_flags
+	 * will initially have the ZIO_FLAG_NODATA bit flag set, but we can't
+	 * check for it here as it is cleared in zio_ready.
+	 */
+	if (zio->io_abd != NULL)
+		abd_put(zio->io_abd);
 }
 
 static zio_t *
@@ -2624,6 +2630,7 @@ zio_write_gang_block(zio_t *pio)
 	int gbh_copies;
 	zio_prop_t zp;
 	int error;
+	boolean_t has_data = !(pio->io_flags & ZIO_FLAG_NODATA);
 
 	/*
 	 * encrypted blocks need DVA[2] free so encrypted gang headers can't
@@ -2636,7 +2643,7 @@ zio_write_gang_block(zio_t *pio)
 	int flags = METASLAB_HINTBP_FAVOR | METASLAB_GANG_HEADER;
 	if (pio->io_flags & ZIO_FLAG_IO_ALLOCATING) {
 		ASSERT(pio->io_priority == ZIO_PRIORITY_ASYNC_WRITE);
-		ASSERT(!(pio->io_flags & ZIO_FLAG_NODATA));
+		ASSERT(has_data);
 
 		flags |= METASLAB_ASYNC_ALLOC;
 		VERIFY(zfs_refcount_held(&mc->mc_alloc_slots[pio->io_allocator],
@@ -2660,7 +2667,7 @@ zio_write_gang_block(zio_t *pio)
 	if (error) {
 		if (pio->io_flags & ZIO_FLAG_IO_ALLOCATING) {
 			ASSERT(pio->io_priority == ZIO_PRIORITY_ASYNC_WRITE);
-			ASSERT(!(pio->io_flags & ZIO_FLAG_NODATA));
+			ASSERT(has_data);
 
 			/*
 			 * If we failed to allocate the gang block header then
@@ -2719,14 +2726,15 @@ zio_write_gang_block(zio_t *pio)
 		bzero(zp.zp_mac, ZIO_DATA_MAC_LEN);
 
 		zio_t *cio = zio_write(zio, spa, txg, &gbh->zg_blkptr[g],
-		    abd_get_offset(pio->io_abd, pio->io_size - resid), lsize,
-		    lsize, &zp, zio_write_gang_member_ready, NULL, NULL,
+		    has_data ? abd_get_offset(pio->io_abd, pio->io_size -
+		    resid) : NULL, lsize, lsize, &zp,
+		    zio_write_gang_member_ready, NULL, NULL,
 		    zio_write_gang_done, &gn->gn_child[g], pio->io_priority,
 		    ZIO_GANG_CHILD_FLAGS(pio), &pio->io_bookmark);
 
 		if (pio->io_flags & ZIO_FLAG_IO_ALLOCATING) {
 			ASSERT(pio->io_priority == ZIO_PRIORITY_ASYNC_WRITE);
-			ASSERT(!(pio->io_flags & ZIO_FLAG_NODATA));
+			ASSERT(has_data);
 
 			/*
 			 * Gang children won't throttle but we should