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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>
This commit is contained in:
Peter Lieven 2015-04-07 22:08:15 +02:00 committed by Stefan Hajnoczi
parent e8d3b1a25f
commit 05b685fbab
1 changed files with 28 additions and 7 deletions
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35
block/iscsi.c
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@ -56,6 +56,7 @@ typedef struct IscsiLun {
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 @@ typedef struct IscsiAIOCB {
#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 @@ static void
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 @@ static void iscsi_detach_aio_context(BlockDriverState *bs)
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 @@ static void iscsi_attach_aio_context(BlockDriverState *bs,
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)