BRT: Fix tests to work on non-empty pools

It should not normally happen, but if it does, better to not fail
everything for no good reason, or it may be hard to debug.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Alexander Motin <mav@FreeBSD.org>
Sponsored by: iXsystems, Inc.
Closes openzfs#16007

tests/zfs-tests/tests/functional/bclone/bclone_common.kshlib

@@ -97,20 +97,19 @@ function verify_pool_prop_eq
 
 function verify_pool_props
 {
-    typeset -r dsize=$1
-    typeset -r ratio=$2
+    typeset -r oused=$1
+    typeset -r osaved=$2
+    typeset dsize=$3
+    typeset ratio=$4
 
     if [[ $dsize -eq 0 ]]; then
-        verify_pool_prop_eq bcloneused 0
-        verify_pool_prop_eq bclonesaved 0
-        verify_pool_prop_eq bcloneratio 1.00
-    else
-        if [[ $ratio -eq 1 ]]; then
-            verify_pool_prop_eq bcloneused 0
-        else
-            verify_pool_prop_eq bcloneused $dsize
-        fi
-        verify_pool_prop_eq bclonesaved $((dsize*(ratio-1)))
+        ratio=1
+    elif [[ $ratio -eq 1 ]]; then
+        dsize=0
+    fi
+    verify_pool_prop_eq bcloneused $(($oused+$dsize))
+    verify_pool_prop_eq bclonesaved $(($osaved+dsize*(ratio-1)))
+    if [[ $oused -eq 0 ]]; then
         verify_pool_prop_eq bcloneratio "${ratio}.00"
     fi
 }
@@ -124,16 +123,22 @@ function bclone_test
     typeset -r srcdir=$4
     typeset -r dstdir=$5
     typeset dsize
+    typeset oused
+    typeset osaved
 
     typeset -r original="${srcdir}/original"
     typeset -r clone="${dstdir}/clone"
 
     log_note "Testing file copy with datatype $datatype, file size $filesize, embedded $embedded"
 
+    # Save current block cloning stats for later use.
+    sync_pool $TESTPOOL
+    oused=$(get_pool_prop bcloneused $TESTPOOL)
+    osaved=$(get_pool_prop bclonesaved $TESTPOOL)
+
     # Create a test file with known content.
     case $datatype in
         random|text)
-            sync_pool $TESTPOOL
             if [[ $datatype = "random" ]]; then
                 dd if=/dev/urandom of=$original bs=$filesize count=1 2>/dev/null
             else
@@ -146,13 +151,13 @@ function bclone_test
             sync_pool $TESTPOOL
             # It is hard to predict block sizes that will be used,
             # so just do one clone and take it from bcloneused.
-            filesize=$(zpool get -Hp -o value bcloneused $TESTPOOL)
+            dsize=$(get_pool_prop bcloneused $TESTPOOL)
+            dsize=$(($dsize-$oused))
             if [[ $embedded = "false" ]]; then
-                log_must test $filesize -gt 0
+                log_must test $dsize -gt 0
             fi
             rm -f "${clone}-tmp"
             sync_pool $TESTPOOL
-            dsize=$filesize
             ;;
         hole)
             log_must truncate_test -s $filesize -f $original
@@ -217,7 +222,7 @@ function bclone_test
     test_file_integrity $original_checksum "${clone}4" $filesize
     test_file_integrity $original_checksum "${clone}5" $filesize
 
-    verify_pool_props $dsize 7
+    verify_pool_props $oused $osaved $dsize 7
 
     # Clear cache and test after fresh import.
     log_must zpool export $TESTPOOL
@@ -240,7 +245,7 @@ function bclone_test
 
     sync_pool $TESTPOOL
 
-    verify_pool_props $dsize 11
+    verify_pool_props $oused $osaved $dsize 11
 
     log_must zpool export $TESTPOOL
     log_must zpool import $TESTPOOL
@@ -268,19 +273,19 @@ function bclone_test
     test_file_integrity $original_checksum "${clone}8" $filesize
     test_file_integrity $original_checksum "${clone}9" $filesize
 
-    verify_pool_props $dsize 6
+    verify_pool_props $oused $osaved $dsize 6
 
     rm -f "${clone}0" "${clone}2" "${clone}4" "${clone}8" "${clone}9"
 
     sync_pool $TESTPOOL
 
     test_file_integrity $original_checksum "${clone}6" $filesize
 
-    verify_pool_props $dsize 1
+    verify_pool_props $oused $osaved $dsize 1
 
     rm -f "${clone}6"
 
     sync_pool $TESTPOOL
 
-    verify_pool_props $dsize 1
+    verify_pool_props $oused $osaved $dsize 1
 }