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Re: [PATCH v2] qemu-config: add error propagation to qemu_config_parse
From: |
Markus Armbruster |
Subject: |
Re: [PATCH v2] qemu-config: add error propagation to qemu_config_parse |
Date: |
Wed, 03 Mar 2021 14:48:20 +0100 |
Paolo Bonzini <pbonzini@redhat.com> writes:
> This enables some simplification of vl.c via error_fatal, and improves
> error messages. Before:
>
> Before:
> $ ./qemu-system-x86_64 -readconfig .
> qemu-system-x86_64: error reading file
> qemu-system-x86_64: -readconfig .: read config .: Invalid argument
> $ /usr/libexec/qemu-kvm -readconfig foo
> qemu-kvm: -readconfig foo: read config foo: No such file or directory
>
> After:
>
> $ ./qemu-system-x86_64 -readconfig .
> qemu-system-x86_64: -readconfig .: error reading file: Is a directory
> $ ./qemu-system-x86_64 -readconfig foo
> qemu-system-x86_64: -readconfig foo: Cannot read config file foo: No such
> file or directory
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Lovely :)
> ---
> block/blkdebug.c | 3 +--
> include/qemu/config-file.h | 5 +++--
> softmmu/vl.c | 29 +++++++++++------------------
> util/qemu-config.c | 23 ++++++++++++-----------
> 4 files changed, 27 insertions(+), 33 deletions(-)
>
> diff --git a/block/blkdebug.c b/block/blkdebug.c
> index 5fe6172da9..7eaa8a28bf 100644
> --- a/block/blkdebug.c
> +++ b/block/blkdebug.c
> @@ -279,9 +279,8 @@ static int read_config(BDRVBlkdebugState *s, const char
> *filename,
> return -errno;
> }
>
> - ret = qemu_config_parse(f, config_groups, filename);
> + ret = qemu_config_parse(f, config_groups, filename, errp);
> if (ret < 0) {
> - error_setg(errp, "Could not parse blkdebug config file");
> goto fail;
> }
> }
> diff --git a/include/qemu/config-file.h b/include/qemu/config-file.h
> index 29226107bd..8d3e53ae4d 100644
> --- a/include/qemu/config-file.h
> +++ b/include/qemu/config-file.h
> @@ -11,9 +11,10 @@ void qemu_add_drive_opts(QemuOptsList *list);
> int qemu_global_option(const char *str);
>
> void qemu_config_write(FILE *fp);
> -int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname);
> +int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname,
> + Error **errp);
>
> -int qemu_read_config_file(const char *filename);
> +int qemu_read_config_file(const char *filename, Error **errp);
>
> /* Parse QDict options as a replacement for a config file (allowing multiple
> enumerated (0..(n-1)) configuration "sections") */
> diff --git a/softmmu/vl.c b/softmmu/vl.c
> index e67f91dd37..e80859c40d 100644
> --- a/softmmu/vl.c
> +++ b/softmmu/vl.c
> @@ -2062,17 +2062,19 @@ static int global_init_func(void *opaque, QemuOpts
> *opts, Error **errp)
> return 0;
> }
>
> -static int qemu_read_default_config_file(void)
> +static void qemu_read_default_config_file(Error **errp)
> {
> + ERRP_GUARD();
> int ret;
> g_autofree char *file = get_relocated_path(CONFIG_QEMU_CONFDIR
> "/qemu.conf");
>
> - ret = qemu_read_config_file(file);
> - if (ret < 0 && ret != -ENOENT) {
> - return ret;
> + ret = qemu_read_config_file(file, errp);
> + if (ret < 0) {
> + if (ret == -ENOENT) {
> + error_free(*errp);
> + *errp = NULL;
> + }
> }
> -
> - return 0;
> }
This change to return void goes against advice in error.h:
* - Whenever practical, also return a value that indicates success /
* failure. This can make the error checking more concise, and can
* avoid useless error object creation and destruction. Note that
* we still have many functions returning void. We recommend
* • bool-valued functions return true on success / false on failure,
* • pointer-valued functions return non-null / null pointer, and
* • integer-valued functions return non-negative / negative.
Tolerable. The only caller wouldn't profit from a return value (it
passes &error_fatal), and more callers seem quite unlikely.
>
> static int qemu_set_option(const char *str)
> @@ -2640,9 +2642,7 @@ void qemu_init(int argc, char **argv, char **envp)
> }
>
> if (userconfig) {
> - if (qemu_read_default_config_file() < 0) {
> - exit(1);
> - }
> + qemu_read_default_config_file(&error_fatal);
> }
>
> /* second pass of option parsing */
> @@ -3330,15 +3330,8 @@ void qemu_init(int argc, char **argv, char **envp)
> qemu_plugin_opt_parse(optarg, &plugin_list);
> break;
> case QEMU_OPTION_readconfig:
> - {
> - int ret = qemu_read_config_file(optarg);
> - if (ret < 0) {
> - error_report("read config %s: %s", optarg,
> - strerror(-ret));
> - exit(1);
> - }
> - break;
> - }
> + qemu_read_config_file(optarg, &error_fatal);
> + break;
> case QEMU_OPTION_spice:
> olist = qemu_find_opts_err("spice", NULL);
> if (!olist) {
> diff --git a/util/qemu-config.c b/util/qemu-config.c
> index e2a700b284..af89df109d 100644
> --- a/util/qemu-config.c
> +++ b/util/qemu-config.c
> @@ -350,7 +350,7 @@ void qemu_config_write(FILE *fp)
> }
>
> /* Returns number of config groups on success, -errno on error */
> -int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname)
> +int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname,
> Error **errp)
> {
> char line[1024], group[64], id[64], arg[64], value[1024];
> Location loc;
> @@ -375,7 +375,7 @@ int qemu_config_parse(FILE *fp, QemuOptsList **lists,
> const char *fname)
> /* group with id */
> list = find_list(lists, group, &local_err);
> if (local_err) {
> - error_report_err(local_err);
> + error_propagate(errp, local_err);
> goto out;
> }
Please avoid error_propagate() where possible:
list = find_list(lists, group, errp);
if (!list) {
goto out;
}
> opts = qemu_opts_create(list, id, 1, NULL);
> @@ -386,7 +386,7 @@ int qemu_config_parse(FILE *fp, QemuOptsList **lists,
> const char *fname)
> /* group without id */
> list = find_list(lists, group, &local_err);
> if (local_err) {
> - error_report_err(local_err);
> + error_propagate(errp, local_err);
> goto out;
> }
Likewise.
> opts = qemu_opts_create(list, NULL, 0, &error_abort);
> @@ -398,21 +398,21 @@ int qemu_config_parse(FILE *fp, QemuOptsList **lists,
> const char *fname)
> sscanf(line, " %63s = \"\"", arg) == 1) {
> /* arg = value */
> if (opts == NULL) {
> - error_report("no group defined");
> + error_setg(errp, "no group defined");
> goto out;
> }
> - if (!qemu_opt_set(opts, arg, value, &local_err)) {
> - error_report_err(local_err);
> + if (!qemu_opt_set(opts, arg, value, errp)) {
> goto out;
> }
> continue;
> }
> - error_report("parse error");
> + error_setg(errp, "parse error");
> goto out;
> }
> if (ferror(fp)) {
> - error_report("error reading file");
> - goto out;
> + loc_pop(&loc);
> + error_setg_errno(errp, errno, "error reading file");
> + return res;
> }
> res = count;
> out:
> @@ -420,16 +420,17 @@ out:
> return res;
> }
>
> -int qemu_read_config_file(const char *filename)
> +int qemu_read_config_file(const char *filename, Error **errp)
> {
> FILE *f = fopen(filename, "r");
> int ret;
>
> if (f == NULL) {
> + error_setg_errno(errp, errno, "Cannot read config file %s",
> filename);
> return -errno;
> }
>
> - ret = qemu_config_parse(f, vm_config_groups, filename);
> + ret = qemu_config_parse(f, vm_config_groups, filename, errp);
> fclose(f);
> return ret;
> }
Not avoiding error_propagate() isn't wrong, so
Reviewed-by: Markus Armbruster <armbru@redhat.com>
But please consider avoiding it anyway.
- Re: [PATCH v2] qemu-config: add error propagation to qemu_config_parse,
Markus Armbruster <=