block/iscsi: handle zero events from iscsi_which_events
newer libiscsi versions may return zero events from iscsi_which_events.
In this case iscsi_service will return immediately without any progress.
To avoid busy waiting for iscsi_which_events to change we deregister all
read and write handlers in this case and schedule a timer to periodically
check iscsi_which_events for changed events.
Next libiscsi version will introduce async reconnects and zero events
are returned while libiscsi is waiting for a reconnect retry.
Signed-off-by: Peter Lieven <pl@kamp.de>
Message-id: 1428437295-29577-1-git-send-email-pl@kamp.de
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/block/iscsi.c b/block/iscsi.c
index 3e34b1f..ba33290 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -56,6 +56,7 @@
uint64_t num_blocks;
int events;
QEMUTimer *nop_timer;
+ QEMUTimer *event_timer;
uint8_t lbpme;
uint8_t lbprz;
uint8_t has_write_same;
@@ -95,6 +96,7 @@
#endif
} IscsiAIOCB;
+#define EVENT_INTERVAL 250
#define NOP_INTERVAL 5000
#define MAX_NOP_FAILURES 3
#define ISCSI_CMD_RETRIES ARRAY_SIZE(iscsi_retry_times)
@@ -256,21 +258,30 @@
iscsi_set_events(IscsiLun *iscsilun)
{
struct iscsi_context *iscsi = iscsilun->iscsi;
- int ev;
+ int ev = iscsi_which_events(iscsi);
- /* We always register a read handler. */
- ev = POLLIN;
- ev |= iscsi_which_events(iscsi);
if (ev != iscsilun->events) {
aio_set_fd_handler(iscsilun->aio_context,
iscsi_get_fd(iscsi),
- iscsi_process_read,
+ (ev & POLLIN) ? iscsi_process_read : NULL,
(ev & POLLOUT) ? iscsi_process_write : NULL,
iscsilun);
-
+ iscsilun->events = ev;
}
- iscsilun->events = ev;
+ /* newer versions of libiscsi may return zero events. In this
+ * case start a timer to ensure we are able to return to service
+ * once this situation changes. */
+ if (!ev) {
+ timer_mod(iscsilun->event_timer,
+ qemu_clock_get_ms(QEMU_CLOCK_REALTIME) + EVENT_INTERVAL);
+ }
+}
+
+static void iscsi_timed_set_events(void *opaque)
+{
+ IscsiLun *iscsilun = opaque;
+ iscsi_set_events(iscsilun);
}
static void
@@ -1214,6 +1225,11 @@
timer_free(iscsilun->nop_timer);
iscsilun->nop_timer = NULL;
}
+ if (iscsilun->event_timer) {
+ timer_del(iscsilun->event_timer);
+ timer_free(iscsilun->event_timer);
+ iscsilun->event_timer = NULL;
+ }
}
static void iscsi_attach_aio_context(BlockDriverState *bs,
@@ -1230,6 +1246,11 @@
iscsi_nop_timed_event, iscsilun);
timer_mod(iscsilun->nop_timer,
qemu_clock_get_ms(QEMU_CLOCK_REALTIME) + NOP_INTERVAL);
+
+ /* Prepare a timer for a delayed call to iscsi_set_events */
+ iscsilun->event_timer = aio_timer_new(iscsilun->aio_context,
+ QEMU_CLOCK_REALTIME, SCALE_MS,
+ iscsi_timed_set_events, iscsilun);
}
static bool iscsi_is_write_protected(IscsiLun *iscsilun)
