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Date: Wed, 22 Nov 2023 20:03:50 -0700
From: Andreas Dilger <adilger@...ger.ca>
To: tytso@....edu
Cc: linux-ext4@...r.kernel.org,
	Andreas Dilger <adilger@...ger.ca>
Subject: [PATCH] tests: make m_assume_storage_prezeroed more robust

Don't assume that mke2fs is going to zero out an exact number
of blocks when run with/without "-E assume_storage_prezeroed",
since this depends on a number of different options that are
not specified in the test script.

Instead, check that the number of blocks zeroed in the image is
a small fraction (1/40th) of the number of blocks zeroed when
"-E assume_sotrage_prezeroed" is not given, which makes it more
robust when running in different environments.  This varies from
1/47 in the original test to 1/91 in my local test environment.

Avoid "losetup --sector-size 4096", use "mke2fs -b 4096" instead.
Clean up the loop device before checking "stat" so that all
blocks are flushed to the backing storage before calling sync.
Only one loop device and test file is needed for the test.

Signed-off-by: Andreas Dilger <adilger@...ger.ca>
---
 tests/m_assume_storage_prezeroed/expect |  2 -
 tests/m_assume_storage_prezeroed/script | 64 ++++++++++++-------------
 2 files changed, 30 insertions(+), 36 deletions(-)
 delete mode 100644 tests/m_assume_storage_prezeroed/expect

diff --git a/tests/m_assume_storage_prezeroed/expect b/tests/m_assume_storage_prezeroed/expect
deleted file mode 100644
index b735e2425..000000000
--- a/tests/m_assume_storage_prezeroed/expect
+++ /dev/null
@@ -1,2 +0,0 @@
-> 10000
-224
diff --git a/tests/m_assume_storage_prezeroed/script b/tests/m_assume_storage_prezeroed/script
index 1a8d84635..eea881428 100644
--- a/tests/m_assume_storage_prezeroed/script
+++ b/tests/m_assume_storage_prezeroed/script
@@ -10,48 +10,44 @@ if test "$(id -u)" -ne 0 ; then
 elif ! command -v losetup >/dev/null ; then
     echo "$test_name: $test_description: skipped (no losetup)"
 else
-    dd if=/dev/zero of=$TMPFILE.1 bs=1 count=0 seek=$FILE_SIZE >> $LOG 2>&1
-    dd if=/dev/zero of=$TMPFILE.2 bs=1 count=0 seek=$FILE_SIZE >> $LOG 2>&1
+    dd if=/dev/zero of=$TMPFILE bs=1 count=0 seek=$FILE_SIZE >> $LOG 2>&1
 
-    LOOP1=$(losetup --show --sector-size 4096 -f $TMPFILE.1)
-    if [ ! -b "$LOOP1" ]; then
-        echo "$test_name: $DESCRIPTION: skipped (no loop devices)"
-        rm -f $TMPFILE.1 $TMPFILE.2
-        exit 0
-    fi
-    LOOP2=$(losetup --show --sector-size 4096 -f $TMPFILE.2)
-    if [ ! -b "$LOOP2" ]; then
-        echo "$test_name: $DESCRIPTION: skipped (no loop devices)"
-        rm -f $TMPFILE.1 $TMPFILE.2
-	losetup -d $LOOP1
-        exit 0
+    LOOP=$(losetup --show -f $TMPFILE)
+    if [ ! -b "$LOOP" ]; then
+         echo "$test_name: $DESCRIPTION: skipped (no loop devices)"
+         rm -f $TMPFILE
+         exit 0
     fi
 
-    echo $MKE2FS -o Linux -t ext4 $LOOP1 >> $LOG 2>&1
-    $MKE2FS -o Linux -t ext4 $LOOP1 >> $LOG 2>&1
+    cmd="$MKE2FS -o Linux -t ext4 -b 4096"
+    echo "$cmd $LOOP" >> $LOG
+    $cmd $LOOP >> $LOG 2>&1
+    losetup -d $LOOP
     sync
-    stat $TMPFILE.1 >> $LOG 2>&1
-    SZ=$(stat -c "%b" $TMPFILE.1)
-    if test $SZ -gt 10000 ; then
-	echo "> 10000" > $OUT
-    else
-	echo "$SZ" > $OUT
+    stat $TMPFILE >> $LOG 2>&1
+    BLOCKS_DEF=$(stat -c "%b" $TMPFILE)
+
+    > $TMPFILE
+    dd if=/dev/zero of=$TMPFILE bs=1 count=0 seek=$FILE_SIZE >> $LOG 2>&1
+    LOOP=$(losetup --show -f $TMPFILE)
+    if [ ! -b "$LOOP" ]; then
+         echo "$test_name: $DESCRIPTION: skipped (no loop devices)"
+         rm -f $TMPFILE
+         exit 0
     fi
 
-    echo $MKE2FS -o Linux -t ext4 -E assume_storage_prezeroed=1 $LOOP2 >> $LOG 2>&1
-    $MKE2FS -o Linux -t ext4 -E assume_storage_prezeroed=1 $LOOP2 >> $LOG 2>&1
+    cmd+=" -E assume_storage_prezeroed=1"
+    echo "$cmd $LOOP" >> $LOG
+    $cmd $TMPFILE >> $LOG 2>&1
+    losetup -d $LOOP
     sync
-    stat $TMPFILE.2 >> $LOG 2>&1
-    stat -c "%b" $TMPFILE.2 >> $OUT
-
-    losetup -d $LOOP1
-    losetup -d $LOOP2
-    rm -f $TMPFILE.1 $TMPFILE.2
+    stat $TMPFILE >> $LOG 2>&1
+    BLOCKS_ASP=$(stat -c "%b" $TMPFILE)
 
-    cmp -s $OUT $EXP
-    status=$?
+    echo "blocks_dev: $BLOCKS_DEF blocks_asp: ${BLOCKS_ASP}" >> $LOG
 
-    if [ "$status" = 0 ] ; then
+    # should use less than 1/20 of the blocks with assume_storage_prezeroed
+    if (( $BLOCKS_DEF > $BLOCKS_ASP * 40 )) ; then
 	echo "$test_name: $test_description: ok"
 	touch $test_name.ok
     else
@@ -60,4 +56,4 @@ else
 	diff $EXP $OUT >> $test_name.failed
     fi
 fi
-unset LOG OUT EXP FILE_SIZE LOOP1 LOOP2
+unset LOG OUT EXP FILE_SIZE LOOP
-- 
2.25.1


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