Revision e35bdc123a4ace9f4d3fccaaf88907014e2438cd authored by Kevin Wolf on 05 October 2018, 16:57:40 UTC, committed by Kevin Wolf on 05 November 2018, 14:09:55 UTC
If a management application builds the block graph node by node, the protocol layer doesn't inherit its read-only option from the format layer any more, so it must be set explicitly. Backing files should work on read-only storage, but at the same time, a block job like commit should be able to reopen them read-write if they are on read-write storage. However, without option inheritance, reopen only changes the read-only option for the root node (typically the format layer), but not the protocol layer, so reopening fails (the format layer wants to get write permissions, but the protocol layer is still read-only). A simple workaround for the problem in the management tool would be to open the protocol layer always read-write and to make only the format layer read-only for backing files. However, sometimes the file is actually stored on read-only storage and we don't know whether the image can be opened read-write (for example, for NBD it depends on the server we're trying to connect to). This adds an option that makes QEMU try to open the image read-write, but allows it to degrade to a read-only mode without returning an error. The documentation for this option is consciously phrased in a way that allows QEMU to switch to a better model eventually: Instead of trying when the image is first opened, making the read-only flag dynamic and changing it automatically whenever the first BLK_PERM_WRITE user is attached or the last one is detached would be much more useful behaviour. Unfortunately, this more useful behaviour is also a lot harder to implement, and libvirt needs a solution now before it can switch to -blockdev, so let's start with this easier approach for now. Instead of adding a new auto-read-only option, turning the existing read-only into an enum (with a bool alternate for compatibility) was considered, but it complicated the implementation to the point that it didn't seem to be worth it. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com>
1 parent eeae6a5
qemu-io.c
/*
* Command line utility to exercise the QEMU I/O path.
*
* Copyright (C) 2009 Red Hat, Inc.
* Copyright (c) 2003-2005 Silicon Graphics, Inc.
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#include "qemu/osdep.h"
#include <getopt.h>
#include <libgen.h>
#ifndef _WIN32
#include <termios.h>
#endif
#include "qapi/error.h"
#include "qemu-io.h"
#include "qemu/error-report.h"
#include "qemu/main-loop.h"
#include "qemu/option.h"
#include "qemu/config-file.h"
#include "qemu/readline.h"
#include "qemu/log.h"
#include "qapi/qmp/qstring.h"
#include "qapi/qmp/qdict.h"
#include "qom/object_interfaces.h"
#include "sysemu/block-backend.h"
#include "block/block_int.h"
#include "trace/control.h"
#include "crypto/init.h"
#include "qemu-version.h"
#define CMD_NOFILE_OK 0x01
static char *progname;
static BlockBackend *qemuio_blk;
static bool quit_qemu_io;
/* qemu-io commands passed using -c */
static int ncmdline;
static char **cmdline;
static bool imageOpts;
static ReadLineState *readline_state;
static int ttyEOF;
static int get_eof_char(void)
{
#ifdef _WIN32
return 0x4; /* Ctrl-D */
#else
struct termios tty;
if (tcgetattr(STDIN_FILENO, &tty) != 0) {
if (errno == ENOTTY) {
return 0x0; /* just expect read() == 0 */
} else {
return 0x4; /* Ctrl-D */
}
}
return tty.c_cc[VEOF];
#endif
}
static int close_f(BlockBackend *blk, int argc, char **argv)
{
blk_unref(qemuio_blk);
qemuio_blk = NULL;
return 0;
}
static const cmdinfo_t close_cmd = {
.name = "close",
.altname = "c",
.cfunc = close_f,
.oneline = "close the current open file",
};
static int openfile(char *name, int flags, bool writethrough, bool force_share,
QDict *opts)
{
Error *local_err = NULL;
if (qemuio_blk) {
error_report("file open already, try 'help close'");
qobject_unref(opts);
return 1;
}
if (force_share) {
if (!opts) {
opts = qdict_new();
}
if (qdict_haskey(opts, BDRV_OPT_FORCE_SHARE)
&& strcmp(qdict_get_str(opts, BDRV_OPT_FORCE_SHARE), "on")) {
error_report("-U conflicts with image options");
qobject_unref(opts);
return 1;
}
qdict_put_str(opts, BDRV_OPT_FORCE_SHARE, "on");
}
qemuio_blk = blk_new_open(name, NULL, opts, flags, &local_err);
if (!qemuio_blk) {
error_reportf_err(local_err, "can't open%s%s: ",
name ? " device " : "", name ?: "");
return 1;
}
blk_set_enable_write_cache(qemuio_blk, !writethrough);
return 0;
}
static void open_help(void)
{
printf(
"\n"
" opens a new file in the requested mode\n"
"\n"
" Example:\n"
" 'open -n -o driver=raw /tmp/data' - opens raw data file read-write, uncached\n"
"\n"
" Opens a file for subsequent use by all of the other qemu-io commands.\n"
" -r, -- open file read-only\n"
" -s, -- use snapshot file\n"
" -C, -- use copy-on-read\n"
" -n, -- disable host cache, short for -t none\n"
" -U, -- force shared permissions\n"
" -k, -- use kernel AIO implementation (on Linux only)\n"
" -t, -- use the given cache mode for the image\n"
" -d, -- use the given discard mode for the image\n"
" -o, -- options to be given to the block driver"
"\n");
}
static int open_f(BlockBackend *blk, int argc, char **argv);
static const cmdinfo_t open_cmd = {
.name = "open",
.altname = "o",
.cfunc = open_f,
.argmin = 1,
.argmax = -1,
.flags = CMD_NOFILE_OK,
.args = "[-rsCnkU] [-t cache] [-d discard] [-o options] [path]",
.oneline = "open the file specified by path",
.help = open_help,
};
static QemuOptsList empty_opts = {
.name = "drive",
.merge_lists = true,
.head = QTAILQ_HEAD_INITIALIZER(empty_opts.head),
.desc = {
/* no elements => accept any params */
{ /* end of list */ }
},
};
static int open_f(BlockBackend *blk, int argc, char **argv)
{
int flags = BDRV_O_UNMAP;
int readonly = 0;
bool writethrough = true;
int c;
int ret;
QemuOpts *qopts;
QDict *opts;
bool force_share = false;
while ((c = getopt(argc, argv, "snCro:kt:d:U")) != -1) {
switch (c) {
case 's':
flags |= BDRV_O_SNAPSHOT;
break;
case 'n':
flags |= BDRV_O_NOCACHE;
writethrough = false;
break;
case 'C':
flags |= BDRV_O_COPY_ON_READ;
break;
case 'r':
readonly = 1;
break;
case 'k':
flags |= BDRV_O_NATIVE_AIO;
break;
case 't':
if (bdrv_parse_cache_mode(optarg, &flags, &writethrough) < 0) {
error_report("Invalid cache option: %s", optarg);
qemu_opts_reset(&empty_opts);
return -EINVAL;
}
break;
case 'd':
if (bdrv_parse_discard_flags(optarg, &flags) < 0) {
error_report("Invalid discard option: %s", optarg);
qemu_opts_reset(&empty_opts);
return -EINVAL;
}
break;
case 'o':
if (imageOpts) {
printf("--image-opts and 'open -o' are mutually exclusive\n");
qemu_opts_reset(&empty_opts);
return -EINVAL;
}
if (!qemu_opts_parse_noisily(&empty_opts, optarg, false)) {
qemu_opts_reset(&empty_opts);
return -EINVAL;
}
break;
case 'U':
force_share = true;
break;
default:
qemu_opts_reset(&empty_opts);
qemuio_command_usage(&open_cmd);
return -EINVAL;
}
}
if (!readonly) {
flags |= BDRV_O_RDWR;
}
if (imageOpts && (optind == argc - 1)) {
if (!qemu_opts_parse_noisily(&empty_opts, argv[optind], false)) {
qemu_opts_reset(&empty_opts);
return -EINVAL;
}
optind++;
}
qopts = qemu_opts_find(&empty_opts, NULL);
opts = qopts ? qemu_opts_to_qdict(qopts, NULL) : NULL;
qemu_opts_reset(&empty_opts);
if (optind == argc - 1) {
ret = openfile(argv[optind], flags, writethrough, force_share, opts);
} else if (optind == argc) {
ret = openfile(NULL, flags, writethrough, force_share, opts);
} else {
qobject_unref(opts);
qemuio_command_usage(&open_cmd);
return -EINVAL;
}
if (ret) {
return -EINVAL;
}
return 0;
}
static int quit_f(BlockBackend *blk, int argc, char **argv)
{
quit_qemu_io = true;
return 0;
}
static const cmdinfo_t quit_cmd = {
.name = "quit",
.altname = "q",
.cfunc = quit_f,
.argmin = -1,
.argmax = -1,
.flags = CMD_FLAG_GLOBAL,
.oneline = "exit the program",
};
static void usage(const char *name)
{
printf(
"Usage: %s [OPTIONS]... [-c STRING]... [file]\n"
"QEMU Disk exerciser\n"
"\n"
" --object OBJECTDEF define an object such as 'secret' for\n"
" passwords and/or encryption keys\n"
" --image-opts treat file as option string\n"
" -c, --cmd STRING execute command with its arguments\n"
" from the given string\n"
" -f, --format FMT specifies the block driver to use\n"
" -r, --read-only export read-only\n"
" -s, --snapshot use snapshot file\n"
" -n, --nocache disable host cache, short for -t none\n"
" -C, --copy-on-read enable copy-on-read\n"
" -m, --misalign misalign allocations for O_DIRECT\n"
" -k, --native-aio use kernel AIO implementation (on Linux only)\n"
" -t, --cache=MODE use the given cache mode for the image\n"
" -d, --discard=MODE use the given discard mode for the image\n"
" -T, --trace [[enable=]<pattern>][,events=<file>][,file=<file>]\n"
" specify tracing options\n"
" see qemu-img(1) man page for full description\n"
" -U, --force-share force shared permissions\n"
" -h, --help display this help and exit\n"
" -V, --version output version information and exit\n"
"\n"
"See '%s -c help' for information on available commands.\n"
"\n"
QEMU_HELP_BOTTOM "\n",
name, name);
}
static char *get_prompt(void)
{
static char prompt[FILENAME_MAX + 2 /*"> "*/ + 1 /*"\0"*/ ];
if (!prompt[0]) {
snprintf(prompt, sizeof(prompt), "%s> ", progname);
}
return prompt;
}
static void GCC_FMT_ATTR(2, 3) readline_printf_func(void *opaque,
const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
vprintf(fmt, ap);
va_end(ap);
}
static void readline_flush_func(void *opaque)
{
fflush(stdout);
}
static void readline_func(void *opaque, const char *str, void *readline_opaque)
{
char **line = readline_opaque;
*line = g_strdup(str);
}
static void completion_match(const char *cmd, void *opaque)
{
readline_add_completion(readline_state, cmd);
}
static void readline_completion_func(void *opaque, const char *str)
{
readline_set_completion_index(readline_state, strlen(str));
qemuio_complete_command(str, completion_match, NULL);
}
static char *fetchline_readline(void)
{
char *line = NULL;
readline_start(readline_state, get_prompt(), 0, readline_func, &line);
while (!line) {
int ch = getchar();
if (ttyEOF != 0x0 && ch == ttyEOF) {
printf("\n");
break;
}
readline_handle_byte(readline_state, ch);
}
return line;
}
#define MAXREADLINESZ 1024
static char *fetchline_fgets(void)
{
char *p, *line = g_malloc(MAXREADLINESZ);
if (!fgets(line, MAXREADLINESZ, stdin)) {
g_free(line);
return NULL;
}
p = line + strlen(line);
if (p != line && p[-1] == '\n') {
p[-1] = '\0';
}
return line;
}
static char *fetchline(void)
{
if (readline_state) {
return fetchline_readline();
} else {
return fetchline_fgets();
}
}
static void prep_fetchline(void *opaque)
{
int *fetchable = opaque;
qemu_set_fd_handler(STDIN_FILENO, NULL, NULL, NULL);
*fetchable= 1;
}
static int command_loop(void)
{
int i, fetchable = 0, prompted = 0;
int ret, last_error = 0;
char *input;
for (i = 0; !quit_qemu_io && i < ncmdline; i++) {
ret = qemuio_command(qemuio_blk, cmdline[i]);
if (ret < 0) {
last_error = ret;
}
}
if (cmdline) {
g_free(cmdline);
return last_error;
}
while (!quit_qemu_io) {
if (!prompted) {
printf("%s", get_prompt());
fflush(stdout);
qemu_set_fd_handler(STDIN_FILENO, prep_fetchline, NULL, &fetchable);
prompted = 1;
}
main_loop_wait(false);
if (!fetchable) {
continue;
}
input = fetchline();
if (input == NULL) {
break;
}
ret = qemuio_command(qemuio_blk, input);
g_free(input);
if (ret < 0) {
last_error = ret;
}
prompted = 0;
fetchable = 0;
}
qemu_set_fd_handler(STDIN_FILENO, NULL, NULL, NULL);
return last_error;
}
static void add_user_command(char *optarg)
{
cmdline = g_renew(char *, cmdline, ++ncmdline);
cmdline[ncmdline-1] = optarg;
}
static void reenable_tty_echo(void)
{
qemu_set_tty_echo(STDIN_FILENO, true);
}
enum {
OPTION_OBJECT = 256,
OPTION_IMAGE_OPTS = 257,
};
static QemuOptsList qemu_object_opts = {
.name = "object",
.implied_opt_name = "qom-type",
.head = QTAILQ_HEAD_INITIALIZER(qemu_object_opts.head),
.desc = {
{ }
},
};
static QemuOptsList file_opts = {
.name = "file",
.implied_opt_name = "file",
.head = QTAILQ_HEAD_INITIALIZER(file_opts.head),
.desc = {
/* no elements => accept any params */
{ /* end of list */ }
},
};
int main(int argc, char **argv)
{
int readonly = 0;
const char *sopt = "hVc:d:f:rsnCmkt:T:U";
const struct option lopt[] = {
{ "help", no_argument, NULL, 'h' },
{ "version", no_argument, NULL, 'V' },
{ "cmd", required_argument, NULL, 'c' },
{ "format", required_argument, NULL, 'f' },
{ "read-only", no_argument, NULL, 'r' },
{ "snapshot", no_argument, NULL, 's' },
{ "nocache", no_argument, NULL, 'n' },
{ "copy-on-read", no_argument, NULL, 'C' },
{ "misalign", no_argument, NULL, 'm' },
{ "native-aio", no_argument, NULL, 'k' },
{ "discard", required_argument, NULL, 'd' },
{ "cache", required_argument, NULL, 't' },
{ "trace", required_argument, NULL, 'T' },
{ "object", required_argument, NULL, OPTION_OBJECT },
{ "image-opts", no_argument, NULL, OPTION_IMAGE_OPTS },
{ "force-share", no_argument, 0, 'U'},
{ NULL, 0, NULL, 0 }
};
int c;
int opt_index = 0;
int flags = BDRV_O_UNMAP;
int ret;
bool writethrough = true;
Error *local_error = NULL;
QDict *opts = NULL;
const char *format = NULL;
char *trace_file = NULL;
bool force_share = false;
#ifdef CONFIG_POSIX
signal(SIGPIPE, SIG_IGN);
#endif
module_call_init(MODULE_INIT_TRACE);
progname = g_path_get_basename(argv[0]);
qemu_init_exec_dir(argv[0]);
qcrypto_init(&error_fatal);
module_call_init(MODULE_INIT_QOM);
qemu_add_opts(&qemu_object_opts);
qemu_add_opts(&qemu_trace_opts);
bdrv_init();
while ((c = getopt_long(argc, argv, sopt, lopt, &opt_index)) != -1) {
switch (c) {
case 's':
flags |= BDRV_O_SNAPSHOT;
break;
case 'n':
flags |= BDRV_O_NOCACHE;
writethrough = false;
break;
case 'C':
flags |= BDRV_O_COPY_ON_READ;
break;
case 'd':
if (bdrv_parse_discard_flags(optarg, &flags) < 0) {
error_report("Invalid discard option: %s", optarg);
exit(1);
}
break;
case 'f':
format = optarg;
break;
case 'c':
add_user_command(optarg);
break;
case 'r':
readonly = 1;
break;
case 'm':
qemuio_misalign = true;
break;
case 'k':
flags |= BDRV_O_NATIVE_AIO;
break;
case 't':
if (bdrv_parse_cache_mode(optarg, &flags, &writethrough) < 0) {
error_report("Invalid cache option: %s", optarg);
exit(1);
}
break;
case 'T':
g_free(trace_file);
trace_file = trace_opt_parse(optarg);
break;
case 'V':
printf("%s version " QEMU_FULL_VERSION "\n"
QEMU_COPYRIGHT "\n", progname);
exit(0);
case 'h':
usage(progname);
exit(0);
case 'U':
force_share = true;
break;
case OPTION_OBJECT: {
QemuOpts *qopts;
qopts = qemu_opts_parse_noisily(&qemu_object_opts,
optarg, true);
if (!qopts) {
exit(1);
}
} break;
case OPTION_IMAGE_OPTS:
imageOpts = true;
break;
default:
usage(progname);
exit(1);
}
}
if ((argc - optind) > 1) {
usage(progname);
exit(1);
}
if (format && imageOpts) {
error_report("--image-opts and -f are mutually exclusive");
exit(1);
}
if (qemu_init_main_loop(&local_error)) {
error_report_err(local_error);
exit(1);
}
qemu_opts_foreach(&qemu_object_opts,
user_creatable_add_opts_foreach,
NULL, &error_fatal);
if (!trace_init_backends()) {
exit(1);
}
trace_init_file(trace_file);
qemu_set_log(LOG_TRACE);
/* initialize commands */
qemuio_add_command(&quit_cmd);
qemuio_add_command(&open_cmd);
qemuio_add_command(&close_cmd);
if (isatty(STDIN_FILENO)) {
ttyEOF = get_eof_char();
readline_state = readline_init(readline_printf_func,
readline_flush_func,
NULL,
readline_completion_func);
qemu_set_tty_echo(STDIN_FILENO, false);
atexit(reenable_tty_echo);
}
/* open the device */
if (!readonly) {
flags |= BDRV_O_RDWR;
}
if ((argc - optind) == 1) {
if (imageOpts) {
QemuOpts *qopts = NULL;
qopts = qemu_opts_parse_noisily(&file_opts, argv[optind], false);
if (!qopts) {
exit(1);
}
opts = qemu_opts_to_qdict(qopts, NULL);
if (openfile(NULL, flags, writethrough, force_share, opts)) {
exit(1);
}
} else {
if (format) {
opts = qdict_new();
qdict_put_str(opts, "driver", format);
}
if (openfile(argv[optind], flags, writethrough,
force_share, opts)) {
exit(1);
}
}
}
ret = command_loop();
/*
* Make sure all outstanding requests complete before the program exits.
*/
bdrv_drain_all();
blk_unref(qemuio_blk);
g_free(readline_state);
if (ret < 0) {
return 1;
} else {
return 0;
}
}
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