svn commit: r358603 - stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs

[Alexander Motin]

Author: mav
Date: Wed Mar  4 04:41:49 2020
New Revision: 358603
URL: https://svnweb.freebsd.org/changeset/base/358603

Log:
  MFC r358339: MFZoL: Fix issue with scanning dedup blocks as scan ends
  
  This patch fixes an issue discovered by ztest where
  dsl_scan_ddt_entry() could add I/Os to the dsl scan queues
  between when the scan had finished all required work and
  when the scan was marked as complete. This caused the scan
  to spin indefinitely without ending.
  
  Reviewed-by: Brian Behlendorf <behlendorf1 at llnl.gov>
  Reviewed-by: Serapheim Dimitropoulos <serapheim.dimitro at delphix.com>
  Reviewed-by: Matthew Ahrens <mahrens at delphix.com>
  Signed-off-by: Tom Caputi <tcaputi at datto.com>
  Closes #8010
  zfsonlinux/zfs at 5e0bd0ae056e26de36dee3c199c6fcff8f14ee15

Modified:
  stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_scan.c
Directory Properties:
  stable/12/   (props changed)

Modified: stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_scan.c
==============================================================================
--- stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_scan.c	Wed Mar  4 04:40:54 2020	(r358602)
+++ stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_scan.c	Wed Mar  4 04:41:49 2020	(r358603)
@@ -2365,6 +2365,20 @@ dsl_scan_ddt_entry(dsl_scan_t *scn, enum zio_checksum 
 	if (!dsl_scan_is_running(scn))
 		return;
 
+	/*
+	 * This function is special because it is the only thing
+	 * that can add scan_io_t's to the vdev scan queues from
+	 * outside dsl_scan_sync(). For the most part this is ok
+	 * as long as it is called from within syncing context.
+	 * However, dsl_scan_sync() expects that no new sio's will
+	 * be added between when all the work for a scan is done
+	 * and the next txg when the scan is actually marked as
+	 * completed. This check ensures we do not issue new sio's
+	 * during this period.
+	 */
+	if (scn->scn_done_txg != 0)
+		return;
+
 	for (p = 0; p < DDT_PHYS_TYPES; p++, ddp++) {
 		if (ddp->ddp_phys_birth == 0 ||
 		    ddp->ddp_phys_birth > scn->scn_phys.scn_max_txg)
@@ -3416,6 +3430,8 @@ dsl_scan_sync(dsl_pool_t *dp, dmu_tx_t *tx)
 				   (longlong_t)tx->tx_txg);
 		}
 	} else if (scn->scn_is_sorted && scn->scn_bytes_pending != 0) {
+		ASSERT(scn->scn_clearing);
+
 		/* need to issue scrubbing IOs from per-vdev queues */
 		scn->scn_zio_root = zio_root(dp->dp_spa, NULL,
 		    NULL, ZIO_FLAG_CANFAIL);