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

[Julien Grall]

Hi Juergen,

On 24/06/2021 10:41, Juergen Gross wrote:
On 16.06.21 16:43, Julien Grall wrote:
From: Julien Grall <jgr...@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 <jgr...@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