[Libguestfs] [nbdkit PATCH] sh: Prefer dd bs=1 over iflag=count_bytes
Eric Blake
eblake at redhat.com
Mon Aug 17 16:35:39 UTC 2020
While iflag=count_bytes combined with bs > 1 allows for more efficient
operation, it is a feature of GNU dd, and not present on other
implementations such as BSD. Sticking to just POSIX features makes
things more portable.
Signed-off-by: Eric Blake <eblake at redhat.com>
---
docs/nbdkit-loop.pod | 2 +-
docs/nbdkit.pod | 4 ++--
plugins/eval/nbdkit-eval-plugin.pod | 6 +++---
plugins/sh/nbdkit-sh-plugin.pod | 2 +-
plugins/sh/assemble.sh | 2 +-
plugins/sh/example.sh | 7 +++----
tests/test-cacheextents.sh | 5 ++---
tests/test-eval-file.sh | 5 ++---
tests/test-eval.sh | 3 +--
tests/test-export-name.sh | 5 ++---
tests/test-parallel-sh.sh | 5 ++---
tests/test-readahead-test-plugin.sh | 2 +-
tests/test-readahead.sh | 1 -
tests/test-retry-reopen-fail.sh | 3 +--
tests/test-retry-size.sh | 3 +--
tests/test-retry.sh | 3 +--
tests/test-shell.sh | 5 ++---
tests/test-single-sh.sh | 3 +--
tests/test-tls-fallback.sh | 2 +-
19 files changed, 28 insertions(+), 40 deletions(-)
diff --git a/docs/nbdkit-loop.pod b/docs/nbdkit-loop.pod
index 055b5750..b21c2212 100644
--- a/docs/nbdkit-loop.pod
+++ b/docs/nbdkit-loop.pod
@@ -120,7 +120,7 @@ creates a disk which contains a bad sector:
echo EIO Bad block >&2
exit 1
else
- dd if=/dev/zero count=$3 iflag=count_bytes
+ dd bs=1 if=/dev/zero count=$3
fi ;;
*) exit 2 ;;
esac
diff --git a/docs/nbdkit.pod b/docs/nbdkit.pod
index 98f069f7..67653bc0 100644
--- a/docs/nbdkit.pod
+++ b/docs/nbdkit.pod
@@ -138,7 +138,7 @@ L<nbdkit-sh-plugin(3)>:
nbdkit sh - <<'EOF'
case "$1" in
get_size) echo 1M ;;
- pread) dd if=/dev/zero count=$3 iflag=count_bytes ;;
+ pread) dd bs=1 if=/dev/zero count=$3 ;;
*) exit 2 ;;
esac
EOF
@@ -149,7 +149,7 @@ The same example as above can be written entirely on the command line
using L<nbdkit-eval-plugin(1)>:
nbdkit eval get_size='echo 1M' \
- pread='dd if=/dev/zero count=$3 iflag=count_bytes'
+ pread='dd bs=1 if=/dev/zero count=$3'
=back
diff --git a/plugins/eval/nbdkit-eval-plugin.pod b/plugins/eval/nbdkit-eval-plugin.pod
index 7126c6de..d5918e28 100644
--- a/plugins/eval/nbdkit-eval-plugin.pod
+++ b/plugins/eval/nbdkit-eval-plugin.pod
@@ -51,7 +51,7 @@ all other methods are identical).
Create a 64M read-only disk of zeroes:
nbdkit eval get_size=' echo 64M ' \
- pread=' dd if=/dev/zero count=$3 iflag=count_bytes '
+ pread=' dd bs=1 if=/dev/zero count=$3 '
The following command is the eval plugin equivalent of
L<nbdkit-file-plugin(1)> (except not as fast and missing many
@@ -60,8 +60,8 @@ features):
nbdkit eval \
config='ln -sf "$(realpath "$3")" $tmpdir/file' \
get_size='stat -Lc %s $tmpdir/file' \
- pread='dd if=$tmpdir/file skip=$4 count=$3 iflag=count_bytes,skip_bytes' \
- pwrite='dd of=$tmpdir/file seek=$4 conv=notrunc oflag=seek_bytes' \
+ pread='dd bs=1 if=$tmpdir/file skip=$4 count=$3' \
+ pwrite='dd bs=1 of=$tmpdir/file seek=$4 conv=notrunc' \
file=disk.img
=head1 PARAMETERS
diff --git a/plugins/sh/nbdkit-sh-plugin.pod b/plugins/sh/nbdkit-sh-plugin.pod
index 07d90b57..70741139 100644
--- a/plugins/sh/nbdkit-sh-plugin.pod
+++ b/plugins/sh/nbdkit-sh-plugin.pod
@@ -42,7 +42,7 @@ as the name of the script, like this:
nbdkit sh - <<'EOF'
case "$1" in
get_size) echo 1M ;;
- pread) dd if=/dev/zero count=$3 iflag=count_bytes ;;
+ pread) dd bs=1 if=/dev/zero count=$3 ;;
*) exit 2 ;;
esac
EOF
diff --git a/plugins/sh/assemble.sh b/plugins/sh/assemble.sh
index 5d994857..45b9b698 100755
--- a/plugins/sh/assemble.sh
+++ b/plugins/sh/assemble.sh
@@ -46,7 +46,7 @@ case "$1" in
echo 512
;;
pread)
- dd if=$b skip=$4 count=$3 iflag=count_bytes,skip_bytes
+ dd bs=1 if=$b skip=$4 count=$3
;;
can_write)
# Default is yes to make it writable (but writes will fail).
diff --git a/plugins/sh/example.sh b/plugins/sh/example.sh
index 4f547db0..03249b27 100755
--- a/plugins/sh/example.sh
+++ b/plugins/sh/example.sh
@@ -117,12 +117,12 @@ case "$1" in
pread)
# Read the requested part of the disk and write to stdout.
- dd iflag=skip_bytes,count_bytes skip=$4 count=$3 if=$f || exit 1
+ dd bs=1 skip=$4 count=$3 if=$f || exit 1
;;
pwrite)
# Copy data from stdin and write it to the disk.
- dd oflag=seek_bytes conv=notrunc seek=$4 of=$f || exit 1
+ dd bs=1 conv=notrunc seek=$4 of=$f || exit 1
;;
can_write)
@@ -162,8 +162,7 @@ case "$1" in
# cache)
# Implement an efficient prefetch, if desired.
# It is intentionally omitted from this example.
- # dd iflag=skip_bytes,count_bytes skip=$4 count=$3 \
- # if=$f of=/dev/null || exit 1
+ # dd bs=1 skip=$4 count=$3 if=$f of=/dev/null || exit 1
# ;;
can_cache)
diff --git a/tests/test-cacheextents.sh b/tests/test-cacheextents.sh
index 9580348c..48de9365 100755
--- a/tests/test-cacheextents.sh
+++ b/tests/test-cacheextents.sh
@@ -1,6 +1,6 @@
#!/usr/bin/env bash
# nbdkit
-# Copyright (C) 2019 Red Hat Inc.
+# Copyright (C) 2019-2020 Red Hat Inc.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
@@ -37,7 +37,6 @@ set -e
requires grep --version
requires qemu-img --version
requires qemu-io --version
-requires dd iflag=count_bytes </dev/null
sock="$(mktemp -u)"
sockurl="nbd+unix:///?socket=$sock"
@@ -71,7 +70,7 @@ case "$1" in
echo ${i}M $block_size $((i%4))
done
;;
- pread) dd if=/dev/zero count=$3 iflag=count_bytes ;;
+ pread) dd bs=1 if=/dev/zero count=$3 ;;
can_write) ;;
pwrite) dd of=/dev/null ;;
can_trim) ;;
diff --git a/tests/test-eval-file.sh b/tests/test-eval-file.sh
index 7d6f79d4..d291803f 100755
--- a/tests/test-eval-file.sh
+++ b/tests/test-eval-file.sh
@@ -39,7 +39,6 @@ set -x
requires guestfish --version
requires test -f disk
-requires dd iflag=count_bytes </dev/null
files="eval-file.img"
rm -f $files
@@ -50,8 +49,8 @@ cp disk eval-file.img
nbdkit -fv -U - eval \
config='ln -sf "$(realpath "$3")" $tmpdir/file' \
get_size='stat -Lc %s $tmpdir/file' \
- pread='dd if=$tmpdir/file skip=$4 count=$3 iflag=count_bytes,skip_bytes' \
- pwrite='dd of=$tmpdir/file seek=$4 conv=notrunc oflag=seek_bytes' \
+ pread='dd bs=1 if=$tmpdir/file skip=$4 count=$3' \
+ pwrite='dd bs=1 of=$tmpdir/file seek=$4 conv=notrunc' \
file=eval-file.img \
--run '
guestfish \
diff --git a/tests/test-eval.sh b/tests/test-eval.sh
index 07a9ea1e..212f2836 100755
--- a/tests/test-eval.sh
+++ b/tests/test-eval.sh
@@ -35,7 +35,6 @@ set -e
set -x
requires qemu-img --version
-requires dd iflag=count_bytes </dev/null
files="eval.out eval.missing"
rm -f $files
@@ -47,7 +46,7 @@ cleanup_fn rm -f $files
# nbdkit, and nbdkit shuts down before the .close callback is called.
nbdkit -U - eval \
get_size='echo 64M' \
- pread='dd if=/dev/zero count=$3 iflag=count_bytes' \
+ pread='dd bs=1 if=/dev/zero count=$3' \
missing='echo "in missing: $@" >> eval.missing; exit 2' \
unload='' \
--run 'qemu-img info $nbd; sleep 10' > eval.out
diff --git a/tests/test-export-name.sh b/tests/test-export-name.sh
index 5ff0d088..40f2ce18 100755
--- a/tests/test-export-name.sh
+++ b/tests/test-export-name.sh
@@ -1,6 +1,6 @@
#!/usr/bin/env bash
# nbdkit
-# Copyright (C) 2019 Red Hat Inc.
+# Copyright (C) 2019-2020 Red Hat Inc.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
@@ -35,7 +35,6 @@ set -e
set -x
requires nbdsh --version
-requires dd iflag=count_bytes </dev/null
sock=`mktemp -u`
files="$sock exportname.pid"
@@ -59,7 +58,7 @@ case "$1" in
echo ${#2}
;;
pread)
- printf %s "$2" | dd skip=$4 count=$3 iflag=skip_bytes,count_bytes
+ printf %s "$2" | dd bs=1 skip=$4 count=$3
;;
*) exit 2 ;;
esac
diff --git a/tests/test-parallel-sh.sh b/tests/test-parallel-sh.sh
index 8d8b9b19..4a26f0a8 100755
--- a/tests/test-parallel-sh.sh
+++ b/tests/test-parallel-sh.sh
@@ -36,7 +36,6 @@ source ./functions.sh
requires test -f file-data
requires qemu-io --version
requires timeout --version
-requires dd iflag=count_bytes </dev/null
nbdkit --dump-plugin sh | grep -q ^thread_model=parallel ||
{ echo "nbdkit lacks support for parallel requests"; exit 77; }
@@ -87,8 +86,8 @@ fi
case \$1 in
thread_model) echo parallel ;;
get_size) stat -L -c %s \$f || exit 1 ;;
- pread) dd iflag=skip_bytes,count_bytes skip=\$4 count=\$3 if=\$f || exit 1 ;;
- pwrite) dd oflag=seek_bytes conv=notrunc seek=\$4 of=\$f || exit 1 ;;
+ pread) dd bs=1 skip=\$4 count=\$3 if=\$f || exit 1 ;;
+ pwrite) dd bs=1 conv=notrunc seek=\$4 of=\$f || exit 1 ;;
can_write) ;;
*) exit 2 ;;
esac
diff --git a/tests/test-readahead-test-plugin.sh b/tests/test-readahead-test-plugin.sh
index e8c57c5c..c2af913c 100755
--- a/tests/test-readahead-test-plugin.sh
+++ b/tests/test-readahead-test-plugin.sh
@@ -40,7 +40,7 @@ case "$1" in
;;
pread)
sleep 5
- dd if=/dev/zero count=$3 iflag=count_bytes
+ dd bs=1 if=/dev/zero count=$3
;;
*)
exit 2
diff --git a/tests/test-readahead.sh b/tests/test-readahead.sh
index b1aabd88..329bcd68 100755
--- a/tests/test-readahead.sh
+++ b/tests/test-readahead.sh
@@ -40,7 +40,6 @@ set -x
requires python3 --version
requires python3 -c 'import nbd'
-requires dd iflag=count_bytes </dev/null
files="readahead.img"
rm -f $files
diff --git a/tests/test-retry-reopen-fail.sh b/tests/test-retry-reopen-fail.sh
index 55704f33..60e579e2 100755
--- a/tests/test-retry-reopen-fail.sh
+++ b/tests/test-retry-reopen-fail.sh
@@ -40,7 +40,6 @@ set -x
fail=0
requires qemu-io --version
-requires dd iflag=count_bytes </dev/null
files="retry-reopen-fail-count retry-reopen-fail-open-count
retry-reopen-fail-status"
@@ -96,7 +95,7 @@ case "$1" in
echo "EIO pread failed" >&2
exit 1
else
- dd if=/dev/zero count=$3 iflag=count_bytes
+ dd bs=1 if=/dev/zero count=$3
fi
;;
diff --git a/tests/test-retry-size.sh b/tests/test-retry-size.sh
index ac3daf69..7ddc20ca 100755
--- a/tests/test-retry-size.sh
+++ b/tests/test-retry-size.sh
@@ -37,7 +37,6 @@ set -x
fail=0
requires qemu-io --version
-requires dd iflag=count_bytes </dev/null
files="retry-size-open-count retry-size-fail"
rm -f $files
@@ -81,7 +80,7 @@ case "$1" in
touch retry-size-fail
fi ;;
esac
- dd if=/dev/zero count=$3 iflag=count_bytes
+ dd bs=1 if=/dev/zero count=$3
;;
*) exit 2 ;;
esac
diff --git a/tests/test-retry.sh b/tests/test-retry.sh
index 173bd20a..fd2513f9 100755
--- a/tests/test-retry.sh
+++ b/tests/test-retry.sh
@@ -35,7 +35,6 @@ set -e
set -x
requires qemu-img --version
-requires dd iflag=count_bytes </dev/null
files="retry.img retry-count retry-open-count"
rm -f $files
@@ -65,7 +64,7 @@ case "$1" in
echo "EIO pread failed" >&2
exit 1
else
- dd if=/dev/zero count=$3 iflag=count_bytes
+ dd bs=1 if=/dev/zero count=$3
fi
;;
diff --git a/tests/test-shell.sh b/tests/test-shell.sh
index 028b8b9c..9bf00204 100755
--- a/tests/test-shell.sh
+++ b/tests/test-shell.sh
@@ -41,8 +41,7 @@ case "$1" in
;;
pread)
- dd iflag=skip_bytes,count_bytes skip=$4 count=$3 if=$f || \
- exit 1
+ dd bs=1 skip=$4 count=$3 if=$f || exit 1
;;
pwrite)
@@ -51,7 +50,7 @@ case "$1" in
*) echo "garbage flags: '$5'" >&2
exit 1;
esac
- dd oflag=seek_bytes conv=notrunc seek=$4 of=$f || exit 1
+ dd bs=1 conv=notrunc seek=$4 of=$f || exit 1
;;
can_write)
;;
diff --git a/tests/test-single-sh.sh b/tests/test-single-sh.sh
index 63f38dff..0342e712 100755
--- a/tests/test-single-sh.sh
+++ b/tests/test-single-sh.sh
@@ -35,7 +35,6 @@ set -e
set -x
requires nbdsh --version
-requires dd iflag=count_bytes </dev/null
files="single-sh.script single-sh.log"
rm -f $files
@@ -60,7 +59,7 @@ fi
cat >single-sh.script <<\EOF
case $1 in
get_size) echo 1m ;;
- pread) dd if=/dev/zero count=$3 iflag=count_bytes ;;
+ pread) dd bs=1 if=/dev/zero count=$3 ;;
*) exit 2 ;;
esac
EOF
diff --git a/tests/test-tls-fallback.sh b/tests/test-tls-fallback.sh
index 4b48c1cb..ededae39 100755
--- a/tests/test-tls-fallback.sh
+++ b/tests/test-tls-fallback.sh
@@ -71,7 +71,7 @@ case $1 in
fi
echo $3 ;;
get_size) echo "$2" | wc -c ;;
- pread) echo "$2" | dd skip=$4 count=$3 iflag=skip_bytes,count_bytes ;;
+ pread) echo "$2" | dd bs=1 skip=$4 count=$3 ;;
can_write | can_trim) exit 0 ;;
*) exit 2 ;;
esac
--
2.28.0
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