Re: [PATCH 09/10] tools/xenstored: Dump delayed requests

[Julien Grall <julien@xen.org>]

Hi Juergen,

On 24/06/2021 10:41, Juergen Gross wrote:
> On 16.06.21 16:43, Julien Grall wrote:
>> From: Julien Grall <jgrall@amazon.com>
>>
>> Currently, only Live-Update request can be delayed. In a follow-up,
>> we will want to delay more requests (e.g. transaction start).
>> Therefore we want to preserve delayed requests across Live-Update.
>>
>> Delayed requests are just complete "in" buffer. So the code is
>> refactored to allow sharing the code to dump "in" buffer.
>>
>> Signed-off-by: Julien Grall <jgrall@amazon.com>
>> ---
>>   tools/xenstore/xenstored_core.c | 42 +++++++++++++++++++++++++--------
>>   1 file changed, 32 insertions(+), 10 deletions(-)
>>
>> diff --git a/tools/xenstore/xenstored_core.c 
>> b/tools/xenstore/xenstored_core.c
>> index 5b7ab7f74013..9eca58682b51 100644
>> --- a/tools/xenstore/xenstored_core.c
>> +++ b/tools/xenstore/xenstored_core.c
>> @@ -2403,25 +2403,47 @@ const char *dump_state_global(FILE *fp)
>>       return NULL;
>>   }
>> +static const char *dump_input_buffered_data(FILE *fp,
>> +                        const struct buffered_data *in,
>> +                        unsigned int *total_len)
>> +{
>> +    unsigned int hlen = in->inhdr ? in->used : sizeof(in->hdr);
>> +
>> +    *total_len += hlen;
>> +    if (fp && fwrite(&in->hdr, hlen, 1, fp) != 1)
>> +        return "Dump read data error";
>> +    if (!in->inhdr && in->used) {
>> +        *total_len += in->used;
>> +        if (fp && fwrite(in->buffer, in->used, 1, fp) != 1)
>> +            return "Dump read data error";
>> +    }
>> +
>> +    return NULL;
>> +}
>> +
>>   /* Called twice: first with fp == NULL to get length, then for 
>> writing data. */
>>   const char *dump_state_buffered_data(FILE *fp, const struct 
>> connection *c,
>>                        struct xs_state_connection *sc)
>>   {
>>       unsigned int len = 0, used;
>> -    struct buffered_data *out, *in = c->in;
>> +    struct buffered_data *out;
>>       bool partial = true;
>> +    struct delayed_request *req;
>> +    const char *ret;
>> -    if (in) {
>> -        len = in->inhdr ? in->used : sizeof(in->hdr);
>> -        if (fp && fwrite(&in->hdr, len, 1, fp) != 1)
>> -            return "Dump read data error";
>> -        if (!in->inhdr && in->used) {
>> -            len += in->used;
>> -            if (fp && fwrite(in->buffer, in->used, 1, fp) != 1)
>> -                return "Dump read data error";
>> -        }
>> +    /* Dump any command that was delayed */
>> +    list_for_each_entry(req, &c->delayed, list) {
> 
> Please add a comment here that the following if() serves especially to
> avoid dumping the data for do_lu_start().

Would you be happy to give your acked-by/reviewed-by if I add the 
following on commit?

"
We only want to preserve commands that wasn't processed at all. All the 
other delayed requests (such as do_lu_start()) must be processed before 
Live-Update.
"

> 
>> +        if (req->func != process_delayed_message)
>> +            continue;
>> +
>> +        assert(!req->in->inhdr);
>> +        if ((ret = dump_input_buffered_data(fp, req->in, &len)))
>> +            return ret;
>>       }
>> +    if (c->in && (ret = dump_input_buffered_data(fp, c->in, &len)))
>> +        return ret;
>> +
>>       if (sc) {
>>           sc->data_in_len = len;
>>           sc->data_resp_len = 0;
>>
> 
> Juergen

Cheers,

-- 
Julien Grall