zio_decompress_data always ASSERTs successful decompression

This interferes with zdb_read_block trying all the decompression
algorithms when the 'd' flag is specified, as some are
expected to fail.  Also control the output when guessing
algorithms, try the more common compression types first, allow
specifying lsize/psize, and fix an uninitialized variable.

Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Paul Zuchowski <pzuchowski@datto.com>
Closes #9612
Closes #9630

tests/runfiles/linux.run

@@ -106,7 +106,7 @@ tags = ['functional', 'clean_mirror']
 
 [tests/functional/cli_root/zdb]
 tests = ['zdb_001_neg', 'zdb_002_pos', 'zdb_003_pos', 'zdb_004_pos',
-    'zdb_005_pos', 'zdb_006_pos', 'zdb_checksum']
+    'zdb_005_pos', 'zdb_006_pos', 'zdb_checksum', 'zdb_decompress']
 pre =
 post =
 tags = ['functional', 'cli_root', 'zdb']

tests/zfs-tests/tests/functional/cli_root/zdb/Makefile.am

@@ -6,4 +6,5 @@ dist_pkgdata_SCRIPTS = \
 	zdb_004_pos.ksh \
 	zdb_005_pos.ksh \
 	zdb_006_pos.ksh \
-	zdb_checksum.ksh
+	zdb_checksum.ksh \
+	zdb_decompress.ksh

tests/zfs-tests/tests/functional/cli_root/zdb/zdb_decompress.ksh

@@ -0,0 +1,119 @@
+#!/bin/ksh
+
+#
+# This file and its contents are supplied under the terms of the
+# Common Development and Distribution License ("CDDL"), version 1.0.
+# You may only use this file in accordance with the terms of version
+# 1.0 of the CDDL.
+#
+# A full copy of the text of the CDDL should have accompanied this
+# source.  A copy of the CDDL is also available via the Internet at
+# http://www.illumos.org/license/CDDL.
+#
+
+#
+# Copyright (c) 2019 by Datto, Inc. All rights reserved.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+#
+# Description:
+# zdb -R pool <DVA>:d will display the correct data and length
+#
+# Strategy:
+# 1. Create a pool, set compression to lzjb
+# 2. Write some identifiable data to a file
+# 3. Run zdb -ddddddbbbbbb against the file
+# 4. Record the DVA, lsize, and psize of L0 block 0
+# 5. Run zdb -R with :d flag and match the data
+# 6. Run zdb -R with :dr flags and match the lsize/psize
+# 7. Run zdb -R with :dr flags and match the lsize
+# 8. Run zdb -R with :dr flags and match the psize
+#
+
+
+function cleanup
+{
+	datasetexists $TESTPOOL && destroy_pool $TESTPOOL
+}
+
+log_assert "Verify zdb -R :d flag (decompress) works as expected"
+log_onexit cleanup
+init_data=$TESTDIR/file1
+write_count=256
+blksize=4096
+pattern="_match__pattern_"
+verify_runnable "global"
+verify_disk_count "$DISKS" 2
+
+default_mirror_setup_noexit $DISKS
+log_must zfs set recordsize=$blksize $TESTPOOL/$TESTFS
+log_must zfs set compression=lzjb $TESTPOOL/$TESTFS
+
+# 16 chars 256 times = 4k = block size
+typeset four_k=""
+for i in {1..$write_count}
+do
+	four_k=$four_k$pattern
+done
+
+# write the 4k block 256 times
+for i in {1..$write_count}
+do
+	echo $four_k >> $init_data
+done
+
+sync_pool $TESTPOOL true
+
+# get object number of file
+listing=$(ls -i $init_data)
+set -A array $listing
+obj=${array[0]}
+log_note "file $init_data has object number $obj"
+
+output=$(zdb -ddddddbbbbbb $TESTPOOL/$TESTFS $obj 2> /dev/null \
+    |grep -m 1 "L0 DVA" |head -n1)
+dva=$(grep -oP 'DVA\[0\]=<\K.*?(?=>)' <<< "$output")
+log_note "block 0 of $init_data has a DVA of $dva"
+
+# use the length reported by zdb -ddddddbbbbbb
+size_str=$(grep -oP 'size=\K.*?(?= )' <<< "$output")
+log_note "block size $size_str"
+
+vdev=$(echo "$dva" |awk '{split($0,array,":")} END{print array[1]}')
+offset=$(echo "$dva" |awk '{split($0,array,":")} END{print array[2]}')
+output=$(zdb -R $TESTPOOL $vdev:$offset:$size_str:d 2> /dev/null)
+echo $output |grep $pattern > /dev/null
+(( $? != 0 )) && log_fail "zdb -R :d failed to decompress the data properly"
+
+output=$(zdb -R $TESTPOOL $vdev:$offset:$size_str:dr 2> /dev/null)
+echo $output |grep $four_k > /dev/null
+(( $? != 0 )) && log_fail "zdb -R :dr failed to decompress the data properly"
+
+output=$(zdb -R $TESTPOOL $vdev:$offset:$size_str:dr 2> /dev/null)
+result=${#output}
+(( $result != $blksize)) && log_fail \
+"zdb -R failed to decompress the data to the length (${#output} != $size_str)"
+
+# decompress using lsize
+lsize=$(echo $size_str |awk '{split($0,array,"/")} END{print array[1]}')
+psize=$(echo $size_str |awk '{split($0,array,"/")} END{print array[2]}')
+output=$(zdb -R $TESTPOOL $vdev:$offset:$lsize:dr 2> /dev/null)
+result=${#output}
+(( $result != $blksize)) && log_fail \
+"zdb -R failed to decompress the data (length ${#output} != $blksize)"
+
+# Specifying psize will decompress successfully , but not always to full
+# lsize since zdb has to guess lsize incrementally.
+output=$(zdb -R $TESTPOOL $vdev:$offset:$psize:dr 2> /dev/null)
+result=${#output}
+# convert psize to decimal
+psize_orig=$psize
+psize=${psize%?}
+psize=$((16#$psize))
+(( $result < $psize)) && log_fail \
+"zdb -R failed to decompress the data with psize $psize_orig\
+ (length ${#output} < $psize)"
+
+log_pass "zdb -R :d flag (decompress) works as expected"