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Re: [PATCH v4 04/13] tools/xenstore: add framework to commit accounting data on success only
Hi Juergen,
On 05/04/2023 08:03, Juergen Gross wrote:
Instead of modifying accounting data and undo those modifications in
case of an error during further processing, add a framework for
collecting the needed changes and commit them only when the whole
operation has succeeded.
This scheme can reuse large parts of the per transaction accounting.
The changed_domain handling can be reused, but the array size of the
accounting data should be possible to be different for both use cases.
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V3:
- call acc_commit() earlier (Julien Grall)
- add assert() to acc_commit()
- use fixed sized acc array in struct changed_domain (Julien Grall)
---
tools/xenstore/xenstored_core.c | 9 ++++--
tools/xenstore/xenstored_core.h | 3 ++
tools/xenstore/xenstored_domain.c | 53 ++++++++++++++++++++++++++++++-
tools/xenstore/xenstored_domain.h | 5 ++-
4 files changed, 66 insertions(+), 4 deletions(-)
diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
index 3ca68681e3..84335f5f3d 100644
--- a/tools/xenstore/xenstored_core.c
+++ b/tools/xenstore/xenstored_core.c
@@ -1023,6 +1023,9 @@ static void send_error(struct connection *conn, int error)
break;
}
}
+
+ acc_drop(conn);
+
send_reply(conn, XS_ERROR, xsd_errors[i].errstring,
strlen(xsd_errors[i].errstring) + 1);
}
@@ -1034,6 +1037,9 @@ void send_reply(struct connection *conn, enum
xsd_sockmsg_type type,
assert(type != XS_WATCH_EVENT);
+ conn->in = NULL;
AFAIU, you are setting conn->in to NULL in order to please..
+ acc_commit(conn);
... this call. However in case of an error like...
+
if ( len > XENSTORE_PAYLOAD_MAX ) { > send_error(conn,
E2BIG);
... here, send_reply() will be called again. But the error will not be
set because conn->in is NULL.
So I think you want to restore conn->in rewrite acc_commit(). The
ordering would also deserve an explanation in a comment.
return;
@@ -1059,8 +1065,6 @@ void send_reply(struct connection *conn, enum
xsd_sockmsg_type type,
}
}
- conn->in = NULL;
-
/* Update relevant header fields and fill in the message body. */
bdata->hdr.msg.type = type;
bdata->hdr.msg.len = len;
@@ -2195,6 +2199,7 @@ struct connection *new_connection(const struct
interface_funcs *funcs)
new->is_stalled = false;
new->transaction_started = 0;
INIT_LIST_HEAD(&new->out_list);
+ INIT_LIST_HEAD(&new->acc_list);
INIT_LIST_HEAD(&new->ref_list);
INIT_LIST_HEAD(&new->watches);
INIT_LIST_HEAD(&new->transaction_list);
diff --git a/tools/xenstore/xenstored_core.h b/tools/xenstore/xenstored_core.h
index c59b06551f..1f811f38cb 100644
--- a/tools/xenstore/xenstored_core.h
+++ b/tools/xenstore/xenstored_core.h
@@ -139,6 +139,9 @@ struct connection
struct list_head out_list;
uint64_t timeout_msec;
+ /* Not yet committed accounting data (valid if in != NULL). */
+ struct list_head acc_list;
+
/* Referenced requests no longer pending. */
struct list_head ref_list;
diff --git a/tools/xenstore/xenstored_domain.c b/tools/xenstore/xenstored_domain.c
index 30fb9acec6..144cbafb73 100644
--- a/tools/xenstore/xenstored_domain.c
+++ b/tools/xenstore/xenstored_domain.c
@@ -91,6 +91,8 @@ struct domain
bool wrl_delay_logged;
};
+#define ACC_CHD_N (ACC_TR_N < ACC_REQ_N ? ACC_REQ_N : ACC_TR_N)
Both ACC_TR_N and ACC_REQ_N are fixed. Can you explain why we need this
magic?
Related, wouldn't it be better to define it in the enum?
+
struct changed_domain
{
/* List of all changed domains. */
@@ -100,7 +102,7 @@ struct changed_domain
unsigned int domid;
/* Accounting data. */
- int acc[ACC_TR_N];
+ int acc[ACC_CHD_N];
};
static struct hashtable *domhash;
@@ -1070,6 +1072,7 @@ static int domain_acc_add(struct connection *conn,
unsigned int domid,
enum accitem what, int add, bool no_dom_alloc)
{
struct domain *d;
+ struct changed_domain *cd;
struct list_head *head;
int ret;
@@ -1090,6 +1093,22 @@ static int domain_acc_add(struct connection *conn, unsigned int domid,
}
}
+ /* Temporary accounting data until final commit? */
+ if (conn && conn->in && what < ACC_REQ_N) {
+ /* Consider transaction local data. */
+ ret = 0;
+ if (conn->transaction && what < ACC_TR_N) {
+ head = transaction_get_changed_domains(
+ conn->transaction);
+ cd = acc_find_changed_domain(head, domid);
+ if (cd)
+ ret = cd->acc[what];
+ }
+ ret += acc_add_changed_dom(conn->in, &conn->acc_list, what,
+ add, domid);
+ return errno ? -1 : domain_acc_add_valid(d, what, ret);
+ }
+
if (conn && conn->transaction && what < ACC_TR_N) {
head = transaction_get_changed_domains(conn->transaction);
ret = acc_add_changed_dom(conn->transaction, head, what,
@@ -1106,6 +1125,38 @@ static int domain_acc_add(struct connection *conn,
unsigned int domid,
return d->acc[what];
}
+void acc_drop(struct connection *conn)
+{
+ struct changed_domain *cd;
+
+ while ((cd = list_top(&conn->acc_list, struct changed_domain, list))) {
+ list_del(&cd->list);
+ talloc_free(cd);
+ }
+}
+
+void acc_commit(struct connection *conn)
+{
+ struct changed_domain *cd;
+ enum accitem what;
+
+ /*
+ * Make sure domain_acc_add() below can't add additional data to
+ * to be committed accounting records.
+ */
+ assert(!conn->in);
+
+ while ((cd = list_top(&conn->acc_list, struct changed_domain, list))) {
+ list_del(&cd->list);
+ for (what = 0; what < ACC_REQ_N; what++)
+ if (cd->acc[what])
+ domain_acc_add(conn, cd->domid, what,
+ cd->acc[what], true);
+
+ talloc_free(cd);
+ }
+}
+
int domain_nbentry_inc(struct connection *conn, unsigned int domid)
{
return (domain_acc_add(conn, domid, ACC_NODES, 1, false) < 0)
diff --git a/tools/xenstore/xenstored_domain.h
b/tools/xenstore/xenstored_domain.h
index 9d05eb01da..6355ad4f37 100644
--- a/tools/xenstore/xenstored_domain.h
+++ b/tools/xenstore/xenstored_domain.h
@@ -25,7 +25,8 @@
* a per transaction array.
*/
enum accitem {
- ACC_NODES,
+ ACC_REQ_N, /* Number of elements per request. */
+ ACC_NODES = ACC_REQ_N,
ACC_TR_N, /* Number of elements per transaction. */
ACC_N = ACC_TR_N, /* Number of elements per domain. */
};
@@ -113,6 +114,8 @@ int domain_get_quota(const void *ctx, struct connection
*conn,
* If "update" is true, "chk_quota" is ignored.
*/
int acc_fix_domains(struct list_head *head, bool chk_quota, bool update);
+void acc_drop(struct connection *conn);
+void acc_commit(struct connection *conn);
/* Write rate limiting */
Cheers,
--
Julien Grall
|
