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[xen master] tools/xenstore: introduce accounting data array for per-domain values



commit 621949547cb6205d4bb47884b40c3786904e6af0
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Tue May 30 10:24:13 2023 +0200
Commit:     Julien Grall <jgrall@xxxxxxxxxx>
CommitDate: Wed Jun 7 12:10:31 2023 +0100

    tools/xenstore: introduce accounting data array for per-domain values
    
    Introduce the scheme of an accounting data array for per-domain
    accounting data and use it initially for the number of nodes owned by
    a domain.
    
    Make the accounting data type to be unsigned int, as no data is allowed
    to be negative at any time.
    
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
---
 tools/xenstore/xenstored_domain.c | 70 +++++++++++++++++++++++----------------
 tools/xenstore/xenstored_domain.h |  3 +-
 2 files changed, 43 insertions(+), 30 deletions(-)

diff --git a/tools/xenstore/xenstored_domain.c 
b/tools/xenstore/xenstored_domain.c
index 5b154dbe27..698b2e5e23 100644
--- a/tools/xenstore/xenstored_domain.c
+++ b/tools/xenstore/xenstored_domain.c
@@ -69,8 +69,8 @@ struct domain
        /* Has domain been officially introduced? */
        bool introduced;
 
-       /* number of entry from this domain in the store */
-       int nbentry;
+       /* Accounting data for this domain. */
+       unsigned int acc[ACC_N];
 
        /* Amount of memory allocated for this domain. */
        int memory;
@@ -246,7 +246,7 @@ static int domain_tree_remove_sub(const void *ctx, struct 
connection *conn,
 
        if (keep_orphans) {
                set_tdb_key(node->name, &key);
-               domain->nbentry--;
+               domain_nbentry_dec(NULL, domain->domid);
                node->perms.p[0].id = priv_domid;
                node->acc.memory = 0;
                domain_nbentry_inc(NULL, priv_domid);
@@ -270,7 +270,7 @@ static int domain_tree_remove_sub(const void *ctx, struct 
connection *conn,
                ret = WALK_TREE_SKIP_CHILDREN;
        }
 
-       return domain->nbentry > 0 ? ret : WALK_TREE_SUCCESS_STOP;
+       return domain->acc[ACC_NODES] ? ret : WALK_TREE_SUCCESS_STOP;
 }
 
 static void domain_tree_remove(struct domain *domain)
@@ -278,7 +278,7 @@ static void domain_tree_remove(struct domain *domain)
        int ret;
        struct walk_funcs walkfuncs = { .enter = domain_tree_remove_sub };
 
-       if (domain->nbentry > 0) {
+       if (domain->acc[ACC_NODES]) {
                ret = walk_node_tree(domain, NULL, "/", &walkfuncs, domain);
                if (ret == WALK_TREE_ERROR_STOP)
                        syslog(LOG_ERR,
@@ -436,7 +436,7 @@ int domain_get_quota(const void *ctx, struct connection 
*conn,
        resp = talloc_asprintf_append(resp, "%-16s: %8d\n", #t, e); \
        if (!resp) return ENOMEM
 
-       ent(nodes, d->nbentry);
+       ent(nodes, d->acc[ACC_NODES]);
        ent(watches, d->nbwatch);
        ent(transactions, ta);
        ent(outstanding, d->nboutstanding);
@@ -1046,8 +1046,27 @@ int domain_adjust_node_perms(struct node *node)
        return 0;
 }
 
-static int domain_nbentry_add(struct connection *conn, unsigned int domid,
-                             int add, bool no_dom_alloc)
+static int domain_acc_add_valid(struct domain *d, enum accitem what, int add)
+{
+       assert(what < ARRAY_SIZE(d->acc));
+
+       if ((add < 0 && -add > d->acc[what]) ||
+           (add > 0 && (INT_MAX - d->acc[what]) < add)) {
+               /*
+                * In a transaction when a node is being added/removed AND the
+                * same node has been added/removed outside the transaction in
+                * parallel, the resulting value will be wrong. This is no
+                * problem, as the transaction will fail due to the resulting
+                * conflict.
+                */
+               return (add < 0) ? 0 : INT_MAX;
+       }
+
+       return d->acc[what] + add;
+}
+
+static int domain_acc_add(struct connection *conn, unsigned int domid,
+                         enum accitem what, int add, bool no_dom_alloc)
 {
        struct domain *d;
        struct list_head *head;
@@ -1070,56 +1089,49 @@ static int domain_nbentry_add(struct connection *conn, 
unsigned int domid,
                }
        }
 
-       if (conn && conn->transaction) {
+       if (conn && conn->transaction && what < ACC_TR_N) {
                head = transaction_get_changed_domains(conn->transaction);
-               ret = acc_add_changed_dom(conn->transaction, head, ACC_NODES,
+               ret = acc_add_changed_dom(conn->transaction, head, what,
                                          add, domid);
                if (errno) {
                        fail_transaction(conn->transaction);
                        return -1;
                }
-               /*
-                * In a transaction when a node is being added/removed AND the
-                * same node has been added/removed outside the transaction in
-                * parallel, the resulting number of nodes will be wrong. This
-                * is no problem, as the transaction will fail due to the
-                * resulting conflict.
-                * In the node remove case the resulting number can be even
-                * negative, which should be avoided.
-                */
-               return max(d->nbentry + ret, 0);
+               return domain_acc_add_valid(d, what, ret);
        }
 
-       d->nbentry += add;
+       d->acc[what] = domain_acc_add_valid(d, what, add);
 
-       return d->nbentry;
+       return d->acc[what];
 }
 
 int domain_nbentry_inc(struct connection *conn, unsigned int domid)
 {
-       return (domain_nbentry_add(conn, domid, 1, false) < 0) ? errno : 0;
+       return (domain_acc_add(conn, domid, ACC_NODES, 1, false) < 0)
+              ? errno : 0;
 }
 
 int domain_nbentry_dec(struct connection *conn, unsigned int domid)
 {
-       return (domain_nbentry_add(conn, domid, -1, true) < 0) ? errno : 0;
+       return (domain_acc_add(conn, domid, ACC_NODES, -1, true) < 0)
+              ? errno : 0;
 }
 
 int domain_nbentry_fix(unsigned int domid, int num, bool update)
 {
        int ret;
 
-       ret = domain_nbentry_add(NULL, domid, update ? num : 0, update);
+       ret = domain_acc_add(NULL, domid, ACC_NODES, update ? num : 0, update);
        if (ret < 0 || update)
                return ret;
 
        return domid_is_unprivileged(domid) ? ret + num : 0;
 }
 
-int domain_nbentry(struct connection *conn)
+unsigned int domain_nbentry(struct connection *conn)
 {
        return domain_is_unprivileged(conn)
-              ? domain_nbentry_add(conn, conn->id, 0, true) : 0;
+              ? domain_acc_add(conn, conn->id, ACC_NODES, 0, true) : 0;
 }
 
 static bool domain_chk_quota(struct domain *domain, int mem)
@@ -1596,7 +1608,7 @@ static int domain_check_acc_init_sub(const void *k, void 
*v, void *arg)
         * If everything is correct incrementing the value for each node will
         * result in dom->nodes being 0 at the end.
         */
-       dom->nodes = -d->nbentry;
+       dom->nodes = -d->acc[ACC_NODES];
 
        if (!hashtable_insert(domains, &dom->domid, dom)) {
                talloc_free(dom);
@@ -1651,7 +1663,7 @@ static int domain_check_acc_cb(const void *k, void *v, 
void *arg)
        if (!d)
                return 0;
 
-       d->nbentry += dom->nodes;
+       d->acc[ACC_NODES] += dom->nodes;
 
        return 0;
 }
diff --git a/tools/xenstore/xenstored_domain.h 
b/tools/xenstore/xenstored_domain.h
index 40803574f6..9d05eb01da 100644
--- a/tools/xenstore/xenstored_domain.h
+++ b/tools/xenstore/xenstored_domain.h
@@ -27,6 +27,7 @@
 enum accitem {
        ACC_NODES,
        ACC_TR_N,               /* Number of elements per transaction. */
+       ACC_N = ACC_TR_N,       /* Number of elements per domain. */
 };
 
 void handle_event(void);
@@ -77,7 +78,7 @@ int domain_alloc_permrefs(struct node_perms *perms);
 int domain_nbentry_inc(struct connection *conn, unsigned int domid);
 int domain_nbentry_dec(struct connection *conn, unsigned int domid);
 int domain_nbentry_fix(unsigned int domid, int num, bool update);
-int domain_nbentry(struct connection *conn);
+unsigned int domain_nbentry(struct connection *conn);
 int domain_memory_add(unsigned int domid, int mem, bool no_quota_check);
 
 /*
--
generated by git-patchbot for /home/xen/git/xen.git#master



 


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