[Libguestfs] [nbdkit PATCH 4/5] server: Move prepare/finalize/close recursion to backend.c
Eric Blake
eblake at redhat.com
Mon Oct 7 14:50:15 UTC 2019
Drop backend_set_handle, and instead use the return value of open to
control that. While open recursion still has to go through filters
(because a filter may change the readonly parameter), the recursion
for prepare/finalize/close fits better in backend.c. This will also
help an upcoming patch better handle prepare/finalize during reopen.
Signed-off-by: Eric Blake <eblake at redhat.com>
---
server/internal.h | 5 +----
server/backend.c | 46 +++++++++++++++++++++++++++++++++++-----------
server/filters.c | 35 ++++++++---------------------------
server/plugins.c | 10 ++--------
4 files changed, 46 insertions(+), 50 deletions(-)
diff --git a/server/internal.h b/server/internal.h
index d4b57419..eb0e30c1 100644
--- a/server/internal.h
+++ b/server/internal.h
@@ -303,7 +303,7 @@ struct backend {
void (*config) (struct backend *, const char *key, const char *value);
void (*config_complete) (struct backend *);
const char *(*magic_config_key) (struct backend *);
- int (*open) (struct backend *, struct connection *conn, int readonly);
+ void *(*open) (struct backend *, struct connection *conn, int readonly);
int (*prepare) (struct backend *, struct connection *conn, void *handle,
int readonly);
int (*finalize) (struct backend *, struct connection *conn, void *handle);
@@ -361,9 +361,6 @@ extern int backend_finalize (struct backend *b, struct connection *conn)
__attribute__((__nonnull__ (1, 2)));
extern void backend_close (struct backend *b, struct connection *conn)
__attribute__((__nonnull__ (1, 2)));
-extern void backend_set_handle (struct backend *b, struct connection *conn,
- void *handle)
- __attribute__((__nonnull__ (1, 2, 3)));
extern bool backend_valid_range (struct backend *b, struct connection *conn,
uint64_t offset, uint32_t count)
__attribute__((__nonnull__ (1, 2)));
diff --git a/server/backend.c b/server/backend.c
index 641af5ff..702c9b96 100644
--- a/server/backend.c
+++ b/server/backend.c
@@ -172,7 +172,6 @@ int
backend_open (struct backend *b, struct connection *conn, int readonly)
{
struct b_conn_handle *h = &conn->handles[b->i];
- int r;
debug ("%s: open readonly=%d", b->name, readonly);
@@ -180,18 +179,22 @@ backend_open (struct backend *b, struct connection *conn, int readonly)
assert (h->can_write == -1);
if (readonly)
h->can_write = 0;
- r = b->open (b, conn, readonly);
- if (r == 0) {
- assert (h->handle != NULL);
- if (b->i) /* A filter must not succeed unless its backend did also */
- assert (conn->handles[b->i - 1].handle);
- }
- else {
- assert (h->handle == NULL);
+
+ /* Most filters will call next_open first, resulting in
+ * inner-to-outer ordering.
+ */
+ h->handle = b->open (b, conn, readonly);
+ debug ("%s: open returned handle %p", b->name, h->handle);
+
+ if (h->handle == NULL) {
if (b->i) /* Do not strand backend if this layer failed */
backend_close (b->next, conn);
+ return -1;
}
- return r;
+
+ if (b->i) /* A filter must not succeed unless its backend did also */
+ assert (conn->handles[b->i - 1].handle);
+ return 0;
}
int
@@ -199,6 +202,14 @@ backend_prepare (struct backend *b, struct connection *conn)
{
struct b_conn_handle *h = &conn->handles[b->i];
+ assert (h->handle);
+
+ /* Call these in order starting from the filter closest to the
+ * plugin, similar to typical .open order.
+ */
+ if (b->i && backend_prepare (b->next, conn) == -1)
+ return -1;
+
debug ("%s: prepare readonly=%d", b->name, h->can_write == 0);
return b->prepare (b, conn, h->handle, h->can_write == 0);
@@ -209,9 +220,19 @@ backend_finalize (struct backend *b, struct connection *conn)
{
struct b_conn_handle *h = &conn->handles[b->i];
+ /* Call these in reverse order to .prepare above, starting from the
+ * filter furthest away from the plugin, and matching .close order.
+ */
+
+ assert (h->handle);
debug ("%s: finalize", b->name);
- return b->finalize (b, conn, h->handle);
+ if (b->finalize (b, conn, h->handle) == -1)
+ return -1;
+
+ if (b->i)
+ return backend_finalize (b->next, conn);
+ return 0;
}
void
@@ -219,10 +240,13 @@ backend_close (struct backend *b, struct connection *conn)
{
struct b_conn_handle *h = &conn->handles[b->i];
+ /* outer-to-inner order, opposite .open */
debug ("%s: close", b->name);
b->close (b, conn, h->handle);
reset_b_conn_handle (h);
+ if (b->i)
+ backend_close (b->next, conn);
}
void
diff --git a/server/filters.c b/server/filters.c
index 0635f0bb..1ac4a5f4 100644
--- a/server/filters.c
+++ b/server/filters.c
@@ -198,28 +198,21 @@ next_open (void *nxdata, int readonly)
return backend_open (b_conn->b, b_conn->conn, readonly);
}
-static int
+static void *
filter_open (struct backend *b, struct connection *conn, int readonly)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
struct b_conn nxdata = { .b = b->next, .conn = conn };
- void *handle;
/* Most filters will call next_open first, resulting in
* inner-to-outer ordering.
*/
- if (f->filter.open) {
- handle = f->filter.open (next_open, &nxdata, readonly);
- if (handle == NULL)
- return -1;
- backend_set_handle (b, conn, handle);
- }
- else {
- if (backend_open (b->next, conn, readonly) == -1)
- return -1;
- backend_set_handle (b, conn, NBDKIT_HANDLE_NOT_NEEDED);
- }
- return 0;
+ if (f->filter.open)
+ return f->filter.open (next_open, &nxdata, readonly);
+ else if (backend_open (b->next, conn, readonly) == -1)
+ return NULL;
+ else
+ return NBDKIT_HANDLE_NOT_NEEDED;
}
static void
@@ -227,10 +220,8 @@ filter_close (struct backend *b, struct connection *conn, void *handle)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
- /* outer-to-inner order, opposite .open */
if (handle && f->filter.close)
f->filter.close (handle);
- backend_close (b->next, conn);
}
/* The next_functions structure contains pointers to backend
@@ -411,12 +402,6 @@ filter_prepare (struct backend *b, struct connection *conn, void *handle,
struct backend_filter *f = container_of (b, struct backend_filter, backend);
struct b_conn nxdata = { .b = b->next, .conn = conn };
- /* Call these in order starting from the filter closest to the
- * plugin, similar to typical .open order.
- */
- if (backend_prepare (b->next, conn) == -1)
- return -1;
-
if (f->filter.prepare &&
f->filter.prepare (&next_ops, &nxdata, handle, readonly) == -1)
return -1;
@@ -430,14 +415,10 @@ filter_finalize (struct backend *b, struct connection *conn, void *handle)
struct backend_filter *f = container_of (b, struct backend_filter, backend);
struct b_conn nxdata = { .b = b->next, .conn = conn };
- /* Call these in reverse order to .prepare above, starting from the
- * filter furthest away from the plugin, and matching .close order.
- */
if (f->filter.finalize &&
f->filter.finalize (&next_ops, &nxdata, handle) == -1)
return -1;
-
- return backend_finalize (b->next, conn);
+ return 0;
}
static int64_t
diff --git a/server/plugins.c b/server/plugins.c
index f309ac22..87daaf26 100644
--- a/server/plugins.c
+++ b/server/plugins.c
@@ -233,20 +233,14 @@ plugin_magic_config_key (struct backend *b)
return p->plugin.magic_config_key;
}
-static int
+static void *
plugin_open (struct backend *b, struct connection *conn, int readonly)
{
struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- void *handle;
assert (p->plugin.open != NULL);
- handle = p->plugin.open (readonly);
- if (!handle)
- return -1;
-
- backend_set_handle (b, conn, handle);
- return 0;
+ return p->plugin.open (readonly);
}
/* We don't expose .prepare and .finalize to plugins since they aren't
--
2.21.0
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