The value '1.1k' is inexact; 1126.4 bytes is not possible, so we happen to truncate it to 1126. Our use of fractional sizes is intended for convenience, but when a user specifies a fraction that is not a clean translation to binary, truncating/rounding behind their backs can cause confusion. Better is to deprecate inexact values, which still leaves '1.5k' as valid, but alerts the user to spell out their values as a precise byte number in cases where they are currently being rounded. Note that values like '0.1G' in the testsuite need adjustment as a result. Since qemu_strtosz() does not have an Err** parameter, and plumbing that in would be a much larger task, we instead go with just directly emitting the deprecation warning to stderr. Signed-off-by: Eric Blake <eblake@redhat.com> --- I'm not a fan of this patch, but am proposing it for discussion purposes. --- docs/system/deprecated.rst | 9 +++++++++ tests/test-cutils.c | 6 +++--- tests/test-keyval.c | 4 ++-- tests/test-qemu-opts.c | 4 ++-- util/cutils.c | 9 +++++++-- 5 files changed, 23 insertions(+), 9 deletions(-) diff --git a/docs/system/deprecated.rst b/docs/system/deprecated.rst index 113c2e933f1b..2c9cb849eec5 100644 --- a/docs/system/deprecated.rst +++ b/docs/system/deprecated.rst @@ -154,6 +154,15 @@ Input parameters that take a size value should only use a size suffix the value is hexadecimal. That is, '0x20M' is deprecated, and should be written either as '32M' or as '0x2000000'. +inexact sizes via scaled fractions (since 6.0) +'''''''''''''''''''''''''''''''''''''''''''''' + +Input parameters that take a size value should only use a fractional +size (such as '1.5M') that will result in an exact byte value. The +use of inexact values (such as '1.1M') that require truncation or +rounding is deprecated, and you should instead consider writing your +unusual size in bytes (here, '1153433' or '1153434' as desired). + QEMU Machine Protocol (QMP) commands ------------------------------------ diff --git a/tests/test-cutils.c b/tests/test-cutils.c index bad3a6099389..c6c33866277b 100644 --- a/tests/test-cutils.c +++ b/tests/test-cutils.c @@ -2124,11 +2124,11 @@ static void test_qemu_strtosz_float(void) g_assert_cmpint(res, ==, 1024); g_assert(endptr == str + 3); - /* For convenience, we permit values that are not byte-exact */ - str = "12.345M"; + /* Fractional values should still be byte-exact */ + str = "12.125M"; err = qemu_strtosz(str, &endptr, &res); g_assert_cmpint(err, ==, 0); - g_assert_cmpint(res, ==, (uint64_t) (12.345 * MiB)); + g_assert_cmpint(res, ==, (uint64_t) (12.125 * MiB)); g_assert(endptr == str + 7); } diff --git a/tests/test-keyval.c b/tests/test-keyval.c index e20c07cf3ea5..7a45c22942e6 100644 --- a/tests/test-keyval.c +++ b/tests/test-keyval.c @@ -525,7 +525,7 @@ static void test_keyval_visit_size(void) visit_free(v); /* Suffixes */ - qdict = keyval_parse("sz1=8b,sz2=1.5k,sz3=2M,sz4=0.1G,sz5=16777215T", + qdict = keyval_parse("sz1=8b,sz2=1.5k,sz3=2M,sz4=0.125G,sz5=16777215T", NULL, NULL, &error_abort); v = qobject_input_visitor_new_keyval(QOBJECT(qdict)); qobject_unref(qdict); @@ -537,7 +537,7 @@ static void test_keyval_visit_size(void) visit_type_size(v, "sz3", &sz, &error_abort); g_assert_cmphex(sz, ==, 2 * MiB); visit_type_size(v, "sz4", &sz, &error_abort); - g_assert_cmphex(sz, ==, GiB / 10); + g_assert_cmphex(sz, ==, GiB / 8); visit_type_size(v, "sz5", &sz, &error_abort); g_assert_cmphex(sz, ==, 16777215ULL * TiB); visit_check_struct(v, &error_abort); diff --git a/tests/test-qemu-opts.c b/tests/test-qemu-opts.c index 6568e31a7229..549e994938fe 100644 --- a/tests/test-qemu-opts.c +++ b/tests/test-qemu-opts.c @@ -720,10 +720,10 @@ static void test_opts_parse_size(void) g_assert_cmphex(qemu_opt_get_size(opts, "size1", 0), ==, 8); g_assert_cmphex(qemu_opt_get_size(opts, "size2", 0), ==, 1536); g_assert_cmphex(qemu_opt_get_size(opts, "size3", 0), ==, 2 * MiB); - opts = qemu_opts_parse(&opts_list_02, "size1=0.1G,size2=16777215T", + opts = qemu_opts_parse(&opts_list_02, "size1=0.125G,size2=16777215T", false, &error_abort); g_assert_cmpuint(opts_count(opts), ==, 2); - g_assert_cmphex(qemu_opt_get_size(opts, "size1", 0), ==, GiB / 10); + g_assert_cmphex(qemu_opt_get_size(opts, "size1", 0), ==, GiB / 8); g_assert_cmphex(qemu_opt_get_size(opts, "size2", 0), ==, 16777215ULL * TiB); /* Beyond limit with suffix */ diff --git a/util/cutils.c b/util/cutils.c index 6a8a175e0d71..1154b9de131a 100644 --- a/util/cutils.c +++ b/util/cutils.c @@ -246,12 +246,13 @@ static int64_t suffix_mul(char suffix, int64_t unit) * The size parsing supports the following syntaxes * - 12345 - decimal, scale determined by @default_suffix and @unit * - 12345{bBkKmMgGtTpPeE} - decimal, scale determined by suffix and @unit - * - 12345.678{kKmMgGtTpPeE} - decimal, scale determined by suffix, and - * fractional portion is truncated to byte + * - 12345.678{kKmMgGtTpPeE} - decimal, scale determined by suffix, if + * fractional portion is exact * - 0x7fEE - hexadecimal, unit determined by @default_suffix * * The following cause a deprecation warning, and may be removed in the future * - 0xabc{kKmMgGtTpP} - hex with scaling suffix + * - 12345.678{kKmMgGtTpPeE} - decimal with inexact fraction that caused truncation * * The following are intentionally not supported * - octal, such as 08 @@ -342,6 +343,10 @@ static int do_strtosz(const char *nptr, const char **end, retval = -ERANGE; goto out; } + if (mul_required && fraction * mul != (uint64_t) (fraction * mul)) { + warn_report("Using a fractional size that is not an exact byte " + "multiple is deprecated: %s", nptr); + } *result = val * mul + (uint64_t) (fraction * mul); retval = 0; -- 2.30.1