[Xen-devel] [PATCH1/1] Fix vreq with error of -EBUSY fails 100 times too soon

["gordongong0350@xxxxxxxxx" <gordongong0350@xxxxxxxxx>]

Fix vreq with error of -EBUSY fails 100 times too soon,  that return EIO to td device layer. If this td

device request is metadata of filesystem, the result is not good at all.

To reproduce it witch  "./iozone -I -s 2G -r 512k -r 1m -r 2m -r 4m -i 0 -i 1 -f /data/iozone_test.tmp",

the result is input/output error & iozone is stopped.

From ccc0ce3aede1f5c920036847ddb16b25969be7ba Mon Sep 17 00:00:00 2001

From: Xiaodong Gong <gordongong0350@xxxxxxxxx>

Date: Fri, 28 Feb 2014 03:01:19 -0500

Subject: [PATCH] fix vreq with error of -EBUSY fails 100 times too soon,

 return EIO to td device layer.

1) all free list is consumed by vreq in one or two block that

   is seted in bat entry.

2) vreq in fail queue, get a chance to run quickly, such as 90us.

---

 tools/blktap2/drivers/tapdisk-vbd.c | 17 ++++++++++++++---

 tools/blktap2/drivers/tapdisk-vbd.h |  1 +

 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/tools/blktap2/drivers/tapdisk-vbd.c b/tools/blktap2/drivers/tapdisk-vbd.c

index c665f27..529eb91 100644

--- a/tools/blktap2/drivers/tapdisk-vbd.c

+++ b/tools/blktap2/drivers/tapdisk-vbd.c

@@ -1081,7 +1081,7 @@ tapdisk_vbd_check_state(td_vbd_t *vbd)

  td_vbd_request_t *vreq, *tmp;

 

  tapdisk_vbd_for_each_request(vreq, tmp, &vbd->failed_requests)

- if (vreq->num_retries >= TD_VBD_MAX_RETRIES)

+ if (vreq->num_retries >= TD_VBD_MAX_RETRIES && vreq->busy_looping != 1 )

  tapdisk_vbd_complete_vbd_request(vbd, vreq);

 

  if (!list_empty(&vbd->new_requests) ||

@@ -1168,7 +1168,7 @@ tapdisk_vbd_complete_vbd_request(td_vbd_t *vbd, td_vbd_request_t *vreq)

 {

  if (!vreq->submitting && !vreq->secs_pending) {

  if (vreq->status == BLKIF_RSP_ERROR &&

-     vreq->num_retries < TD_VBD_MAX_RETRIES &&

+     (vreq->num_retries < TD_VBD_MAX_RETRIES || vreq->busy_looping == 1)&&

      !td_flag_test(vbd->state, TD_VBD_DEAD) &&

      !td_flag_test(vbd->state, TD_VBD_SHUTDOWN_REQUESTED))

  tapdisk_vbd_move_request(vreq, &vbd->failed_requests);

@@ -1450,17 +1450,28 @@ tapdisk_vbd_reissue_failed_requests(td_vbd_t *vbd)

  gettimeofday(&now, NULL);

 

  tapdisk_vbd_for_each_request(vreq, tmp, &vbd->failed_requests) {

+ uint64_t delta = 0;

+

  if (vreq->secs_pending)

  continue;

 

  if (td_flag_test(vbd->state, TD_VBD_SHUTDOWN_REQUESTED))

  goto fail;

 

+ if (vreq->num_retries > TD_VBD_MAX_RETRIES - 10) {

+ delta = (now.tv_sec - vreq->last_try.tv_sec) * 1000000\

+ + now.tv_usec - vreq->last_try.tv_usec;

+ if (delta * vreq->num_retries < TD_VBD_RETRY_INTERVAL)

+ vreq->busy_looping = 1;

+ else

+ vreq->busy_looping = 0;

+ }

+

  if (vreq->error != -EBUSY &&

      now.tv_sec - vreq->last_try.tv_sec < TD_VBD_RETRY_INTERVAL)

  continue;

 

- if (vreq->num_retries >= TD_VBD_MAX_RETRIES) {

+ if (vreq->num_retries >= TD_VBD_MAX_RETRIES && vreq->busy_looping != 1) {

  fail:

  DBG(TLOG_INFO, "req %"PRIu64"retried %d times\n",

      vreq->req.id, vreq->num_retries);

diff --git a/tools/blktap2/drivers/tapdisk-vbd.h b/tools/blktap2/drivers/tapdisk-vbd.h

index be084b2..9e5f5f6 100644

--- a/tools/blktap2/drivers/tapdisk-vbd.h

+++ b/tools/blktap2/drivers/tapdisk-vbd.h

@@ -73,6 +73,7 @@ struct td_vbd_request {

  int                         submitting;

  int                         secs_pending;

  int                         num_retries;

+ int                         busy_looping;

  struct timeval              last_try;

 

  td_vbd_t                   *vbd;

-- 

1.8.3.1

---

gordongong0350@xxxxxxxxx

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