Commit 05b685fb authored by Peter Lieven's avatar Peter Lieven Committed by Stefan Hajnoczi
Browse files

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: default avatarPeter Lieven <pl@kamp.de>
Message-id: 1428437295-29577-1-git-send-email-pl@kamp.de
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent e8d3b1a2

block/iscsi.c

+27 −6
Original line number Diff line number Diff line
@@ -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;

    }



    /* 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);

    }

}



    iscsilun->events = ev;

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)