6294 GRUB should try all DVAs

Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Approved by: Richard Lowe <richlowe@richlowe.net>

usr/src/grub/capability

@@ -19,7 +19,7 @@
 # CDDL HEADER END
 #
 # Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
-# Copyright (c) 2013 by Delphix. All rights reserved.
+# Copyright (c) 2013, 2015 by Delphix. All rights reserved.
 # Copyright 2013 Saso Kiselkov.  All rights reserved.
 #
 # This file defines the current capabilities of GRUB over and above that
@@ -30,7 +30,7 @@
 # GRUB necessitating that the boot blocks be reinstalled for that fix or
 # enhancement to take effect.
 #
-VERSION=25
+VERSION=26
 dboot
 xVM
 zfs

usr/src/grub/grub-0.97/stage2/fsys_zfs.c

@@ -23,7 +23,7 @@
  */
 
 /*
- * Copyright (c) 2013 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
  */
 
@@ -368,17 +368,23 @@ zio_read_data(blkptr_t *bp, void *buf, char *stack)
 			continue;
 
 		if (DVA_GET_GANG(&bp->blk_dva[i])) {
-			if (zio_read_gang(bp, &bp->blk_dva[i], buf, stack) == 0)
-				return (0);
+			if (zio_read_gang(bp, &bp->blk_dva[i], buf, stack) != 0)
+				continue;
 		} else {
 			/* read in a data block */
 			offset = DVA_GET_OFFSET(&bp->blk_dva[i]);
 			sector = DVA_OFFSET_TO_PHYS_SECTOR(offset);
-			if (devread(sector, 0, psize, buf) != 0)
-				return (0);
+			if (devread(sector, 0, psize, buf) == 0)
+				continue;
+		}
+
+		/* verify that the checksum matches */
+		if (zio_checksum_verify(bp, buf, psize) == 0) {
+			return (0);
 		}
 	}
 
+	grub_printf("could not read block due to EIO or ECKSUM\n");
 	return (1);
 }
 
@@ -499,11 +505,6 @@ zio_read(blkptr_t *bp, void *buf, char *stack)
 		return (ERR_FSYS_CORRUPT);
 	}
 
-	if (zio_checksum_verify(bp, buf, psize) != 0) {
-		grub_printf("checksum verification failed\n");
-		return (ERR_FSYS_CORRUPT);
-	}
-
 	if (comp != ZIO_COMPRESS_OFF) {
 		if (decomp_table[comp].decomp_func(buf, retbuf, psize,
 		    lsize) != 0) {