Fix dynamic gang block headers on raidz and mirror devices

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <alexander.motin@TrueNAS.com>
Signed-off-by: Paul Dagnelie <paul.dagnelie@klarasystems.com>
Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Closes openzfs#17587

Author: pcd1193182

include/sys/vdev.h

@@ -139,6 +139,7 @@ extern uint64_t vdev_asize_to_psize_txg(vdev_t *vd, uint64_t asize,
 extern uint64_t vdev_psize_to_asize_txg(vdev_t *vd, uint64_t psize,
     uint64_t txg);
 extern uint64_t vdev_psize_to_asize(vdev_t *vd, uint64_t psize);
+extern uint64_t vdev_get_min_alloc(vdev_t *vd);
 
 /*
  * Return the amount of space allocated for a gang block header.  Note that
@@ -151,6 +152,19 @@ vdev_gang_header_asize(vdev_t *vd)
 	return (vdev_psize_to_asize_txg(vd, SPA_OLD_GANGBLOCKSIZE, 0));
 }
 
+/*
+ * Return the amount of data that can be stored in a gang header. Because we
+ * need to ensure gang headers can always be allocated (as long as there is
+ * space available), this is the minimum allocatable size on the vdev. Note that
+ * since the physical birth txg is not provided, this must be constant for
+ * a given vdev.  (e.g. raidz expansion can't change this)
+ */
+static inline uint64_t
+vdev_gang_header_psize(vdev_t *vd)
+{
+	return (vdev_get_min_alloc(vd));
+}
+
 extern int vdev_fault(spa_t *spa, uint64_t guid, vdev_aux_t aux);
 extern int vdev_degrade(spa_t *spa, uint64_t guid, vdev_aux_t aux);
 extern int vdev_online(spa_t *spa, uint64_t guid, uint64_t flags,

include/sys/vdev_impl.h

@@ -621,7 +621,6 @@ extern uint64_t vdev_default_asize(vdev_t *vd, uint64_t psize, uint64_t txg);
 extern uint64_t vdev_default_min_asize(vdev_t *vd);
 extern uint64_t vdev_get_min_asize(vdev_t *vd);
 extern void vdev_set_min_asize(vdev_t *vd);
-extern uint64_t vdev_get_min_alloc(vdev_t *vd);
 extern uint64_t vdev_get_nparity(vdev_t *vd);
 extern uint64_t vdev_get_ndisks(vdev_t *vd);
 

module/zfs/zio.c

@@ -2956,8 +2956,8 @@ zio_gang_tree_assemble(zio_t *gio, blkptr_t *bp, zio_gang_node_t **gnpp)
 		for (int dva = 0; dva < BP_GET_NDVAS(bp); dva++) {
 			vdev_t *vd = vdev_lookup_top(gio->io_spa,
 			    DVA_GET_VDEV(&bp->blk_dva[dva]));
-			uint64_t asize = vdev_gang_header_asize(vd);
-			gangblocksize = MIN(gangblocksize, asize);
+			uint64_t psize = vdev_gang_header_psize(vd);
+			gangblocksize = MIN(gangblocksize, psize);
 		}
 		spa_config_exit(gio->io_spa, SCL_VDEV, FTAG);
 	} else {

module/zfs/zio_checksum.c

@@ -569,7 +569,11 @@ zio_checksum_error(zio_t *zio, zio_bad_cksum_t *info)
 		    SPA_OLD_GANGBLOCKSIZE, offset, info);
 		if (error == 0) {
 			ASSERT3U(zio->io_child_type, ==, ZIO_CHILD_VDEV);
-			zio_t *pio = zio_unique_parent(zio);
+			zio_t *pio;
+			for (pio = zio_unique_parent(zio);
+			    pio->io_child_type != ZIO_CHILD_GANG;
+			    pio = zio_unique_parent(pio))
+				;
 			zio_gang_node_t *gn = pio->io_private;
 			gn->gn_gangblocksize = SPA_OLD_GANGBLOCKSIZE;
 		}