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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v4 13/19] tools/xenstore: introduce read_node_const()
Introduce a read_node() variant returning a pointer to const struct
node, which doesn't do a copy of the node data after retrieval from
the data base.
Call this variant where appropriate.
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V3:
- new approach (Julien Grall)
V4:
- fix patch subject (Julien Grall)
- let read_node_helper() return a bool (Julien Grall)
---
tools/xenstore/xenstored_core.c | 105 ++++++++++++++++++++++--------
tools/xenstore/xenstored_core.h | 2 +
tools/xenstore/xenstored_domain.c | 4 +-
tools/xenstore/xenstored_watch.c | 10 +--
tools/xenstore/xenstored_watch.h | 3 +-
5 files changed, 90 insertions(+), 34 deletions(-)
diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
index c8c8c4b8f4..f8e5e7b697 100644
--- a/tools/xenstore/xenstored_core.c
+++ b/tools/xenstore/xenstored_core.c
@@ -706,11 +706,11 @@ void db_delete(struct connection *conn, const char *name,
* If it fails, returns NULL and sets errno.
* Temporary memory allocations will be done with ctx.
*/
-struct node *read_node(struct connection *conn, const void *ctx,
- const char *name)
+static struct node *read_node_alloc(struct connection *conn, const void *ctx,
+ const char *name,
+ const struct node_hdr **hdr)
{
size_t size;
- const struct node_hdr *hdr;
struct node *node;
const char *db_name;
int err;
@@ -720,17 +720,16 @@ struct node *read_node(struct connection *conn, const
void *ctx,
errno = ENOMEM;
return NULL;
}
+
node->name = talloc_strdup(node, name);
if (!node->name) {
- talloc_free(node);
errno = ENOMEM;
- return NULL;
+ goto error;
}
db_name = transaction_prepend(conn, name);
- hdr = db_fetch(db_name, &size);
-
- if (hdr == NULL) {
+ *hdr = db_fetch(db_name, &size);
+ if (*hdr == NULL) {
node->hdr.generation = NO_GENERATION;
err = access_node(conn, node, NODE_ACCESS_READ, NULL);
errno = err ? : ENOENT;
@@ -740,31 +739,80 @@ struct node *read_node(struct connection *conn, const
void *ctx,
node->parent = NULL;
/* Datalen, childlen, number of permissions */
- node->hdr = *hdr;
- node->acc.domid = perms_from_node_hdr(hdr)->id;
+ node->hdr = **hdr;
+ node->acc.domid = perms_from_node_hdr(*hdr)->id;
node->acc.memory = size;
- /* Copy node data to new memory area, starting with permissions. */
- size -= sizeof(*hdr);
- node->perms = talloc_memdup(node, perms_from_node_hdr(hdr), size);
- if (node->perms == NULL) {
- errno = ENOMEM;
- goto error;
- }
+ return node;
+
+ error:
+ talloc_free(node);
+ return NULL;
+}
+static bool read_node_helper(struct connection *conn, struct node *node)
+{
/* Data is binary blob (usually ascii, no nul). */
- node->data = node->perms + hdr->num_perms;
+ node->data = node->perms + node->hdr.num_perms;
/* Children is strings, nul separated. */
node->children = node->data + node->hdr.datalen;
if (domain_adjust_node_perms(node))
- goto error;
+ return false;
/* If owner is gone reset currently accounted memory size. */
if (node->acc.domid != get_node_owner(node))
node->acc.memory = 0;
if (access_node(conn, node, NODE_ACCESS_READ, NULL))
+ return false;
+
+ return true;
+}
+
+struct node *read_node(struct connection *conn, const void *ctx,
+ const char *name)
+{
+ size_t size;
+ const struct node_hdr *hdr;
+ struct node *node;
+
+ node = read_node_alloc(conn, ctx, name, &hdr);
+ if (!node)
+ return NULL;
+
+ /* Copy node data to new memory area, starting with permissions. */
+ size = node->acc.memory - sizeof(*hdr);
+ node->perms = talloc_memdup(node, perms_from_node_hdr(hdr), size);
+ if (node->perms == NULL) {
+ errno = ENOMEM;
+ goto error;
+ }
+
+ if (!read_node_helper(conn, node))
+ goto error;
+
+ return node;
+
+ error:
+ talloc_free(node);
+ return NULL;
+}
+
+const struct node *read_node_const(struct connection *conn, const void *ctx,
+ const char *name)
+{
+ const struct node_hdr *hdr;
+ struct node *node;
+
+ node = read_node_alloc(conn, ctx, name, &hdr);
+ if (!node)
+ return NULL;
+
+ /* Unfortunately node->perms isn't const. */
+ node->perms = (void *)perms_from_node_hdr(hdr);
+
+ if (!read_node_helper(conn, node))
goto error;
return node;
@@ -900,13 +948,13 @@ char *get_parent(const void *ctx, const char *node)
static int ask_parents(struct connection *conn, const void *ctx,
const char *name, unsigned int *perm)
{
- struct node *node;
+ const struct node *node;
do {
name = get_parent(ctx, name);
if (!name)
return errno;
- node = read_node(conn, ctx, name);
+ node = read_node_const(conn, ctx, name);
if (node)
break;
if (read_node_can_propagate_errno())
@@ -3197,9 +3245,8 @@ static int dump_state_node_err(struct dump_node_data
*data, const char *err)
}
static int dump_state_node(const void *ctx, struct connection *conn,
- struct node *node, void *arg)
+ const struct node *node, struct dump_node_data *data)
{
- struct dump_node_data *data = arg;
FILE *fp = data->fp;
unsigned int pathlen;
struct xs_state_record_header head;
@@ -3244,14 +3291,20 @@ static int dump_state_node(const void *ctx, struct
connection *conn,
return WALK_TREE_OK;
}
+static int dump_state_node_enter(const void *ctx, struct connection *conn,
+ struct node *node, void *arg)
+{
+ return dump_state_node(ctx, conn, node, arg);
+}
+
static int dump_state_special_node(FILE *fp, const void *ctx,
struct dump_node_data *data,
const char *name)
{
- struct node *node;
+ const struct node *node;
int ret;
- node = read_node(NULL, ctx, name);
+ node = read_node_const(NULL, ctx, name);
if (!node)
return dump_state_node_err(data, "Dump node read node error");
@@ -3267,7 +3320,7 @@ const char *dump_state_nodes(FILE *fp, const void *ctx)
.fp = fp,
.err = "Dump node walk error"
};
- struct walk_funcs walkfuncs = { .enter = dump_state_node };
+ struct walk_funcs walkfuncs = { .enter = dump_state_node_enter };
if (walk_node_tree(ctx, NULL, "/", &walkfuncs, &data))
return data.err;
diff --git a/tools/xenstore/xenstored_core.h b/tools/xenstore/xenstored_core.h
index cbed412a86..07c59c07b7 100644
--- a/tools/xenstore/xenstored_core.h
+++ b/tools/xenstore/xenstored_core.h
@@ -292,6 +292,8 @@ int write_node_raw(struct connection *conn, const char
*db_name,
/* Get a node from the data base. */
struct node *read_node(struct connection *conn, const void *ctx,
const char *name);
+const struct node *read_node_const(struct connection *conn, const void *ctx,
+ const char *name);
/* Remove a node and its children. */
int rm_node(struct connection *conn, const void *ctx, const char *name);
diff --git a/tools/xenstore/xenstored_domain.c
b/tools/xenstore/xenstored_domain.c
index c00ea397cf..1bf138c8b1 100644
--- a/tools/xenstore/xenstored_domain.c
+++ b/tools/xenstore/xenstored_domain.c
@@ -563,12 +563,12 @@ static void domain_tree_remove(struct domain *domain)
static void fire_special_watches(const char *name)
{
void *ctx = talloc_new(NULL);
- struct node *node;
+ const struct node *node;
if (!ctx)
return;
- node = read_node(NULL, ctx, name);
+ node = read_node_const(NULL, ctx, name);
if (node)
fire_watches(NULL, ctx, name, node, true, NULL);
diff --git a/tools/xenstore/xenstored_watch.c b/tools/xenstore/xenstored_watch.c
index 5767675e04..d6e5a4be1e 100644
--- a/tools/xenstore/xenstored_watch.c
+++ b/tools/xenstore/xenstored_watch.c
@@ -73,11 +73,11 @@ static const char *get_watch_path(const struct watch
*watch, const char *name)
* changed permissions we need to take the old permissions into account, too.
*/
static bool watch_permitted(struct connection *conn, const void *ctx,
- const char *name, struct node *node,
+ const char *name, const struct node *node,
struct node_perms *perms)
{
unsigned int perm;
- struct node *parent;
+ const struct node *parent;
char *parent_name;
if (perms) {
@@ -87,7 +87,7 @@ static bool watch_permitted(struct connection *conn, const
void *ctx,
}
if (!node) {
- node = read_node(conn, ctx, name);
+ node = read_node_const(conn, ctx, name);
if (!node)
return false;
}
@@ -101,7 +101,7 @@ static bool watch_permitted(struct connection *conn, const
void *ctx,
parent_name = get_parent(ctx, node->name);
if (!parent_name)
return false;
- parent = read_node(conn, ctx, parent_name);
+ parent = read_node_const(conn, ctx, parent_name);
if (!parent)
return false;
}
@@ -119,7 +119,7 @@ static bool watch_permitted(struct connection *conn, const
void *ctx,
* watch event, too.
*/
void fire_watches(struct connection *conn, const void *ctx, const char *name,
- struct node *node, bool exact, struct node_perms *perms)
+ const struct node *node, bool exact, struct node_perms *perms)
{
struct connection *i;
struct buffered_data *req;
diff --git a/tools/xenstore/xenstored_watch.h b/tools/xenstore/xenstored_watch.h
index 091890edca..ea247997ad 100644
--- a/tools/xenstore/xenstored_watch.h
+++ b/tools/xenstore/xenstored_watch.h
@@ -28,7 +28,8 @@ int do_unwatch(const void *ctx, struct connection *conn,
/* Fire all watches: !exact means all the children are affected (ie. rm). */
void fire_watches(struct connection *conn, const void *tmp, const char *name,
- struct node *node, bool exact, struct node_perms *perms);
+ const struct node *node, bool exact,
+ struct node_perms *perms);
void conn_delete_all_watches(struct connection *conn);
--
2.35.3
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