xemu-project/xemu
1
0
Fork 0
mirror of https://github.com/xemu-project/xemu.git synced 2024-11-24 03:59:52 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

block/iscsi: handle BUSY condition

Browse Source 
this patch adds handling of BUSY status reponse from an iSCSI target.
Currently, we fail with -EIO in case of SCSI_STATUS_BUSY while the
obvious reaction would be to retry the operation after some time.
The retry time is randomly choosen from a range with exponential
growth increasing with each retry.

This patch includes most of the changes by a an upcoming patch
from Stefan Hajnoczi:

 iscsi: implement .bdrv_detach/attach_aio_context()

because I also need the reference to the aio_context for
the retry timer to work. I included the changes to maintain
better mergeability.

Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Peter Lieven 2014-05-30 23:36:47 +02:00 committed by Paolo Bonzini
parent af44da87e9
commit efc6de0d0e
1 changed files with 43 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

55
block/iscsi.c
View File

@ -26,6 +26,7 @@
#include "config-host.h"
#include <poll.h>
#include <math.h>
#include <arpa/inet.h>
#include "qemu-common.h"
#include "qemu/config-file.h"
@ -75,6 +76,7 @@ typedef struct IscsiTask {
Coroutine *co;
QEMUBH *bh;
IscsiLun *iscsilun;
QEMUTimer retry_timer;
} IscsiTask;
typedef struct IscsiAIOCB {
@ -86,7 +88,6 @@ typedef struct IscsiAIOCB {
uint8_t *buf;
int status;
int canceled;
int retries;
int64_t sector_num;
int nb_sectors;
#ifdef __linux__
@ -96,7 +97,8 @@ typedef struct IscsiAIOCB {
#define NOP_INTERVAL 5000
#define MAX_NOP_FAILURES 3
#define ISCSI_CMD_RETRIES 5
#define ISCSI_CMD_RETRIES ARRAY_SIZE(iscsi_retry_times)
static const unsigned iscsi_retry_times[] = {8, 32, 128, 512, 2048};
/* this threshhold is a trade-off knob to choose between
* the potential additional overhead of an extra GET_LBA_STATUS request
@ -146,6 +148,19 @@ static void iscsi_co_generic_bh_cb(void *opaque)
qemu_coroutine_enter(iTask->co, NULL);
}
static void iscsi_retry_timer_expired(void *opaque)
{
struct IscsiTask *iTask = opaque;
if (iTask->co) {
qemu_coroutine_enter(iTask->co, NULL);
}
}
static inline unsigned exp_random(double mean)
{
return -mean * log((double)rand() / RAND_MAX);
}
static void
iscsi_co_generic_cb(struct iscsi_context *iscsi, int status,
void *command_data, void *opaque)
@ -158,14 +173,30 @@ iscsi_co_generic_cb(struct iscsi_context *iscsi, int status,
iTask->do_retry = 0;
iTask->task = task;
if (iTask->retries-- > 0 && status == SCSI_STATUS_CHECK_CONDITION
&& task->sense.key == SCSI_SENSE_UNIT_ATTENTION) {
error_report("iSCSI CheckCondition: %s", iscsi_get_error(iscsi));
iTask->do_retry = 1;
goto out;
}
if (status != SCSI_STATUS_GOOD) {
if (iTask->retries++ < ISCSI_CMD_RETRIES) {
if (status == SCSI_STATUS_CHECK_CONDITION
&& task->sense.key == SCSI_SENSE_UNIT_ATTENTION) {
error_report("iSCSI CheckCondition: %s",
iscsi_get_error(iscsi));
iTask->do_retry = 1;
goto out;
}
if (status == SCSI_STATUS_BUSY) {
unsigned retry_time =
exp_random(iscsi_retry_times[iTask->retries - 1]);
error_report("iSCSI Busy (retry #%u in %u ms): %s",
iTask->retries, retry_time,
iscsi_get_error(iscsi));
aio_timer_init(iTask->iscsilun->aio_context,
&iTask->retry_timer, QEMU_CLOCK_REALTIME,
SCALE_MS, iscsi_retry_timer_expired, iTask);
timer_mod(&iTask->retry_timer,
qemu_clock_get_ms(QEMU_CLOCK_REALTIME) + retry_time);
iTask->do_retry = 1;
return;
}
}
error_report("iSCSI Failure: %s", iscsi_get_error(iscsi));
}
@ -180,9 +211,9 @@ out:
static void iscsi_co_init_iscsitask(IscsiLun *iscsilun, struct IscsiTask *iTask)
{
*iTask = (struct IscsiTask) {
.co = qemu_coroutine_self(),
.retries = ISCSI_CMD_RETRIES,
.iscsilun = iscsilun,
.co = qemu_coroutine_self(),
.retries = ISCSI_CMD_RETRIES,
.iscsilun = iscsilun,
};
}