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Fix for TARGET RESET race

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It can happen, when a device added after blocking, so unblocking then
will make dev->block_count of the new device negative.



git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@5468 d57e44dd-8a1f-0410-8b47-8ef2f437770f
This commit is contained in:
Vladislav Bolkhovitin
2014-04-24 04:03:51 +00:00
parent d3fcdde388
commit 1249be6247
4 changed files with 51 additions and 13 deletions
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1
scst/include/scst.h
View File

@@ -2311,6 +2311,7 @@ struct scst_mgmt_cmd {
unsigned int needs_unblocking:1;
unsigned int lun_set:1; /* set, if lun field is valid */
unsigned int cmd_sn_set:1; /* set, if cmd_sn field is valid */
unsigned int scst_get_called:1; /* set, if scst_get() was called */
/* Set if dev handler's task_mgmt_fn_received was called */
unsigned int task_mgmt_fn_received_called:1;
unsigned int mcmd_dropped:1; /* set if mcmd was dropped */

2
scst/src/scst_lib.c
View File

@@ -5884,7 +5884,7 @@ void scst_free_mgmt_cmd(struct scst_mgmt_cmd *mcmd)
scst_sess_put(mcmd->sess);
if (mcmd->mcmd_tgt_dev != NULL)
if ((mcmd->mcmd_tgt_dev != NULL) || mcmd->scst_get_called)
scst_put(mcmd->cpu_cmd_counter);
mempool_free(mcmd, scst_mgmt_mempool);

4
scst/src/scst_main.c
View File

@@ -960,8 +960,8 @@ int scst_suspend_activity(unsigned long timeout)
set_bit(SCST_FLAG_SUSPENDED, &scst_flags);
/*
* Assignment of SCST_FLAG_SUSPENDING and SCST_FLAG_SUSPENDED must be
* ordered with cpu_cmd_count in scst_get(). Otherwise lockless logic in
* scst_translate_lun() and scst_mgmt_translate_lun() won't work.
* ordered with cpu_cmd_count in scst_get(). Otherwise, lockless logic
* of scst_get() users won't work.
*/
smp_mb__after_set_bit();

57
scst/src/scst_targ.c
View File

@@ -4926,21 +4926,16 @@ void scst_cmd_tasklet(long p)
}
/*
* Returns 0 on success, < 0 if there is no device handler or
* > 0 if SCST_FLAG_SUSPENDED set and SCST_FLAG_SUSPENDING - not.
* No locks, protection is done by the suspended activity.
* Returns 0 on success, or > 0 if SCST_FLAG_SUSPENDED set and
* SCST_FLAG_SUSPENDING - not. No locks, protection is done by the
* suspended activity.
*/
static int scst_mgmt_translate_lun(struct scst_mgmt_cmd *mcmd)
static int scst_get_mgmt(struct scst_mgmt_cmd *mcmd)
{
struct scst_tgt_dev *tgt_dev;
struct list_head *head;
int res = -1;
int res = 0;
TRACE_ENTRY();
TRACE_DBG("Finding tgt_dev for mgmt cmd %p (lun %lld)", mcmd,
(long long unsigned int)mcmd->lun);
mcmd->cpu_cmd_counter = scst_get();
if (unlikely(test_bit(SCST_FLAG_SUSPENDED, &scst_flags) &&
@@ -4951,6 +4946,33 @@ static int scst_mgmt_translate_lun(struct scst_mgmt_cmd *mcmd)
goto out;
}
out:
TRACE_EXIT_HRES(res);
return res;
}
/*
* Returns 0 on success, < 0 if there is no device handler or
* > 0 if SCST_FLAG_SUSPENDED set and SCST_FLAG_SUSPENDING - not.
* No locks, protection is done by the suspended activity.
*/
static int scst_mgmt_translate_lun(struct scst_mgmt_cmd *mcmd)
{
struct scst_tgt_dev *tgt_dev;
struct list_head *head;
int res;
TRACE_ENTRY();
TRACE_DBG("Finding tgt_dev for mgmt cmd %p (lun %lld)", mcmd,
(long long unsigned int)mcmd->lun);
res = scst_get_mgmt(mcmd);
if (unlikely(res != 0))
goto out;
res = -1;
head = &mcmd->sess->sess_tgt_dev_list[SESS_TGT_DEV_LIST_HASH_FN(mcmd->lun)];
list_for_each_entry(tgt_dev, head, sess_tgt_dev_list_entry) {
if (tgt_dev->lun == mcmd->lun) {
@@ -5762,6 +5784,21 @@ static int scst_mgmt_cmd_init(struct scst_mgmt_cmd *mcmd)
}
case SCST_TARGET_RESET:
/*
* Needed to protect against race, when a device added after
* blocking, so unblocking then will make dev->block_count
* of the new device negative.
*/
rc = scst_get_mgmt(mcmd);
if (rc == 0) {
mcmd->state = SCST_MCMD_STATE_EXEC;
mcmd->scst_get_called = 1;
} else {
EXTRACHECKS_BUG_ON(rc < 0);
res = rc;
}
break;
case SCST_NEXUS_LOSS_SESS:
case SCST_ABORT_ALL_TASKS_SESS:
case SCST_NEXUS_LOSS: