Re: [PATCH 4/6] cpus: Improve error messages on memsave, pmemsave write error

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 13/5/24 16:45, Markus Armbruster wrote:
> Philippe Mathieu-Daudé <philmd@linaro.org> writes:
> 
>> On 13/5/24 16:17, Markus Armbruster wrote:
>>> qmp_memsave() and qmp_pmemsave() report fwrite() error as
>>>       An IO error has occurred
>>> Improve this to
>>>       writing memory to '<filename>' failed
>>> Signed-off-by: Markus Armbruster <armbru@redhat.com>
>>> ---
>>>    system/cpus.c | 6 ++++--
>>>    1 file changed, 4 insertions(+), 2 deletions(-)
>>> diff --git a/system/cpus.c b/system/cpus.c
>>> index 68d161d96b..f8fa78f33d 100644
>>> --- a/system/cpus.c
>>> +++ b/system/cpus.c
>>> @@ -813,7 +813,8 @@ void qmp_memsave(int64_t addr, int64_t size, const char *filename,
>>>                goto exit;
>>>            }
>>>            if (fwrite(buf, 1, l, f) != l) {
>>> -            error_setg(errp, QERR_IO_ERROR);
>>> +            error_setg(errp, "writing memory to '%s' failed",
>>> +                       filename);
>>>                goto exit;
>>>            }
>>>            addr += l;
>>> @@ -843,7 +844,8 @@ void qmp_pmemsave(int64_t addr, int64_t size, const char *filename,
>>>                l = size;
>>>            cpu_physical_memory_read(addr, buf, l);
>>>            if (fwrite(buf, 1, l, f) != l) {
>>> -            error_setg(errp, QERR_IO_ERROR);
>>> +            error_setg(errp, "writing memory to '%s' failed",
>>> +                       filename);
>>
>> What about including errno with error_setg_errno()?
> 
> Sure fwrite() fails with errno reliably set?  The manual page doesn't
> mention it...

Indeed. I can see some uses in the code base:

qemu-io-cmds.c:409:    if (ferror(f)) {
qemu-io-cmds.c-410-        perror(file_name);

qga/commands-posix.c-632-    write_count = fwrite(buf, 1, count, fh);
qga/commands-posix.c:633:    if (ferror(fh)) {
qga/commands-posix.c-634-        error_setg_errno(errp, errno, "failed 
to write to file");

util/qemu-config.c:152:    if (ferror(fp)) {
util/qemu-config.c-153-        loc_pop(&loc);
util/qemu-config.c-154-        error_setg_errno(errp, errno, "Cannot 
read config file");

Regardless,

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>