[Qemu-devel] [PATCH] qemu-img: add conv=notrunc option to dd

[Reda Sallahi <fullmanet@gmail.com>]

This adds the conv=notrunc option to dd which tells dd to not truncate the
output.

For the time being we make it mandatory to specify conv=notrunc.

Signed-off-by: Reda Sallahi <fullmanet@gmail.com>
---
 qemu-img-cmds.hx       |  4 ++--
 qemu-img.c             | 31 ++++++++++++++++++++++++++++---
 qemu-img.texi          | 15 +++++++++------
 tests/qemu-iotests/158 |  2 +-
 tests/qemu-iotests/159 |  3 ++-
 tests/qemu-iotests/160 |  7 ++++---
 6 files changed, 46 insertions(+), 16 deletions(-)

diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx
index f054599..18685ac 100644
--- a/qemu-img-cmds.hx
+++ b/qemu-img-cmds.hx
@@ -46,9 +46,9 @@ STEXI
 ETEXI
 
 DEF("dd", img_dd,
-    "dd [--image-opts] [-f fmt] [-O output_fmt] [bs=block_size] [count=blocks] [skip=blocks] if=input of=output")
+    "dd [--image-opts] [-f fmt] [-O output_fmt] [bs=block_size] [count=blocks] [skip=blocks] [conv=notrunc] if=input of=output")
 STEXI
-@item dd [--image-opts] [-f @var{fmt}] [-O @var{output_fmt}] [bs=@var{block_size}] [count=@var{blocks}] [skip=@var{blocks}] if=@var{input} of=@var{output}
+@item dd [--image-opts] [-f @var{fmt}] [-O @var{output_fmt}] [bs=@var{block_size}] [count=@var{blocks}] [skip=@var{blocks}] [conv=notrunc] if=@var{input} of=@var{output}
 ETEXI
 
 DEF("info", img_info,
diff --git a/qemu-img.c b/qemu-img.c
index 3adec86..16b56b8 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -174,7 +174,8 @@ static void QEMU_NORETURN help(void)
            "  'count=N' copy only N input blocks\n"
            "  'if=FILE' read from FILE\n"
            "  'of=FILE' write to FILE\n"
-           "  'skip=N' skip N bs-sized blocks at the start of input\n";
+           "  'skip=N' skip N bs-sized blocks at the start of input\n"
+           "  'conv=notrunc' do not truncate the output file\n";
 
     printf("%s\nSupported formats:", help_msg);
     bdrv_iterate_format(format_print, NULL);
@@ -3807,10 +3808,12 @@ out:
 #define C_IF      04
 #define C_OF      010
 #define C_SKIP    020
+#define C_CONV    040
 
 struct DdInfo {
     unsigned int flags;
     int64_t count;
+    unsigned int conv;
 };
 
 struct DdIo {
@@ -3894,6 +3897,21 @@ static int img_dd_skip(const char *arg,
     return 0;
 }
 
+#define C_NOTRUNC 01
+
+static int img_dd_conv(const char *arg,
+                       struct DdIo *in, struct DdIo *out,
+                       struct DdInfo *dd)
+{
+    if (!strcmp(arg, "notrunc")) {
+        dd->conv |= C_NOTRUNC;
+        return 0;
+    } else {
+        error_report("invalid conversion: '%s'", arg);
+        return 1;
+    }
+}
+
 static int img_dd(int argc, char **argv)
 {
     int ret = 0;
@@ -3909,10 +3927,11 @@ static int img_dd(int argc, char **argv)
     const char *out_fmt = "raw";
     const char *fmt = NULL;
     int64_t size = 0;
-    int64_t block_count = 0, out_pos, in_pos;
+    int64_t out_pos, in_pos;
     struct DdInfo dd = {
         .flags = 0,
         .count = 0,
+        .conv = 0
     };
     struct DdIo in = {
         .bsz = 512, /* Block size is by default 512 bytes */
@@ -3933,6 +3952,7 @@ static int img_dd(int argc, char **argv)
         { "if", img_dd_if, C_IF },
         { "of", img_dd_of, C_OF },
         { "skip", img_dd_skip, C_SKIP },
+        { "conv", img_dd_conv, C_CONV },
         { NULL, NULL, 0 }
     };
     const struct option long_options[] = {
@@ -3997,6 +4017,11 @@ static int img_dd(int argc, char **argv)
         g_free(arg);
         arg = NULL;
     }
+    if (!(dd.conv & C_NOTRUNC)) {
+        error_report("conv=notrunc not specified");
+        ret = -1;
+        goto out;
+    }
 
     if (!(dd.flags & C_IF && dd.flags & C_OF)) {
         error_report("Must specify both input and output files");
@@ -4091,7 +4116,7 @@ static int img_dd(int argc, char **argv)
 
     in.buf = g_new(uint8_t, in.bsz);
 
-    for (out_pos = 0; in_pos < size; block_count++) {
+    for (out_pos = 0; in_pos < size; ) {
         int in_ret, out_ret;
 
         if (in_pos + in.bsz > size) {
diff --git a/qemu-img.texi b/qemu-img.texi
index 174aae3..891af14 100644
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -144,15 +144,18 @@ Parameters to dd subcommand:
 @table @option
 
 @item bs=@var{block_size}
-defines the block size
+Defines the block size.
 @item count=@var{blocks}
-sets the number of input blocks to copy
+Sets the number of input blocks to copy.
 @item if=@var{input}
-sets the input file
+Sets the input file.
 @item of=@var{output}
-sets the output file
+Sets the output file. dd truncates the output file to zero if 'conv=notrunc'
+is not specified.
 @item skip=@var{blocks}
-sets the number of input blocks to skip
+Sets the number of input blocks to skip.
+@item conv=notrunc
+Makes dd not truncate output file to zero.
 @end table
 
 Command description:
@@ -326,7 +329,7 @@ skipped. This is useful for formats such as @code{rbd} if the target
 volume has already been created with site specific options that cannot
 be supplied through qemu-img.
 
-@item dd [-f @var{fmt}] [-O @var{output_fmt}] [bs=@var{block_size}] [count=@var{blocks}] [skip=@var{blocks}] if=@var{input} of=@var{output}
+@item dd [-f @var{fmt}] [-O @var{output_fmt}] [bs=@var{block_size}] [count=@var{blocks}] [skip=@var{blocks}] [conv=notrunc] if=@var{input} of=@var{output}
 
 Dd copies from @var{input} file to @var{output} file converting it from
 @var{fmt} format to @var{output_fmt} format.
diff --git a/tests/qemu-iotests/158 b/tests/qemu-iotests/158
index 5b335db..63e2a10 100755
--- a/tests/qemu-iotests/158
+++ b/tests/qemu-iotests/158
@@ -53,7 +53,7 @@ $QEMU_IO -c "write -P 0xa 0 $size" "$TEST_IMG" | _filter_qemu_io
 echo
 echo "== Converting the image with dd =="
 
-$QEMU_IMG dd if="$TEST_IMG" of="$TEST_IMG.out" -O "$IMGFMT"
+$QEMU_IMG dd if="$TEST_IMG" of="$TEST_IMG.out" conv=notrunc -O "$IMGFMT"
 TEST_IMG="$TEST_IMG.out" _check_test_img
 
 echo
diff --git a/tests/qemu-iotests/159 b/tests/qemu-iotests/159
index 825f05f..d68a19f 100755
--- a/tests/qemu-iotests/159
+++ b/tests/qemu-iotests/159
@@ -55,7 +55,8 @@ for bs in $TEST_SIZES; do
     echo
     echo "== Converting the image with dd with a block size of $bs =="
 
-    $QEMU_IMG dd if="$TEST_IMG" of="$TEST_IMG.out" bs=$bs -O "$IMGFMT"
+    $QEMU_IMG dd if="$TEST_IMG" of="$TEST_IMG.out" bs=$bs conv=notrunc \
+        -O "$IMGFMT"
     TEST_IMG="$TEST_IMG.out" _check_test_img
 
     echo
diff --git a/tests/qemu-iotests/160 b/tests/qemu-iotests/160
index 5c910e5..53b3c30 100755
--- a/tests/qemu-iotests/160
+++ b/tests/qemu-iotests/160
@@ -55,10 +55,11 @@ for skip in $TEST_SKIP_BLOCKS; do
     echo
     echo "== Converting the image with dd with skip=$skip =="
 
-    $QEMU_IMG dd if="$TEST_IMG" of="$TEST_IMG.out" skip="$skip" -O "$IMGFMT" \
-        2> /dev/null
+    $QEMU_IMG dd if="$TEST_IMG" of="$TEST_IMG.out" skip="$skip" conv=notrunc  \
+        -O "$IMGFMT" 2> /dev/null
     TEST_IMG="$TEST_IMG.out" _check_test_img
-    dd if="$TEST_IMG" of="$TEST_IMG.out.dd" skip="$skip" status=none
+    dd if="$TEST_IMG" of="$TEST_IMG.out.dd" skip="$skip" conv=notrunc \
+        status=none
 
     echo
     echo "== Compare the images with qemu-img compare =="
-- 
2.9.2