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Subject[PATCH 14/17] lustre/ptlrpc: re-enqueue ptlrpcd worker
Date
From: Liang Zhen <liang.zhen@intel.com>

osc_extent_wait can be stuck in scenario like this:

1) thread-1 held an active extent
2) thread-2 called flush cache, and marked this extent as "urgent"
and "sync_wait"
3) thread-3 wants to write to the same extent, osc_extent_find will
get "conflict" because this extent is "sync_wait", so it starts
to wait...
4) cl_writeback_work has been scheduled by thread-4 to write some
other extents, it has sent RPCs but not returned yet.
5) thread-1 finished his work, and called osc_extent_release()->
osc_io_unplug_async()->ptlrpcd_queue_work(), but found
cl_writeback_work is still running, so it's ignored (-EBUSY)
6) thread-3 is stuck because nobody will wake him up.

This patch allows ptlrpcd_work to be rescheduled, so it will not
miss request anymore

Signed-off-by: Liang Zhen <liang.zhen@intel.com>
Reviewed-on: http://review.whamcloud.com/8922
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4509
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
---
drivers/staging/lustre/lustre/ptlrpc/client.c | 64 +++++++++++++++++----------
1 file changed, 40 insertions(+), 24 deletions(-)

diff --git a/drivers/staging/lustre/lustre/ptlrpc/client.c b/drivers/staging/lustre/lustre/ptlrpc/client.c
index 7b97c64..4c9e006 100644
--- a/drivers/staging/lustre/lustre/ptlrpc/client.c
+++ b/drivers/staging/lustre/lustre/ptlrpc/client.c
@@ -48,6 +48,7 @@
#include "ptlrpc_internal.h"

static int ptlrpc_send_new_req(struct ptlrpc_request *req);
+static int ptlrpcd_check_work(struct ptlrpc_request *req);

/**
* Initialize passed in client structure \a cl.
@@ -1784,6 +1785,10 @@ interpret:

ptlrpc_req_interpret(env, req, req->rq_status);

+ if (ptlrpcd_check_work(req)) {
+ atomic_dec(&set->set_remaining);
+ continue;
+ }
ptlrpc_rqphase_move(req, RQ_PHASE_COMPLETE);

CDEBUG(req->rq_reqmsg != NULL ? D_RPCTRACE : 0,
@@ -2957,22 +2962,50 @@ EXPORT_SYMBOL(ptlrpc_sample_next_xid);
* have delay before it really runs by ptlrpcd thread.
*/
struct ptlrpc_work_async_args {
- __u64 magic;
int (*cb)(const struct lu_env *, void *);
void *cbdata;
};

-#define PTLRPC_WORK_MAGIC 0x6655436b676f4f44ULL /* magic code */
+static void ptlrpcd_add_work_req(struct ptlrpc_request *req)
+{
+ /* re-initialize the req */
+ req->rq_timeout = obd_timeout;
+ req->rq_sent = cfs_time_current_sec();
+ req->rq_deadline = req->rq_sent + req->rq_timeout;
+ req->rq_reply_deadline = req->rq_deadline;
+ req->rq_phase = RQ_PHASE_INTERPRET;
+ req->rq_next_phase = RQ_PHASE_COMPLETE;
+ req->rq_xid = ptlrpc_next_xid();
+ req->rq_import_generation = req->rq_import->imp_generation;
+
+ ptlrpcd_add_req(req, PDL_POLICY_ROUND, -1);
+}

static int work_interpreter(const struct lu_env *env,
struct ptlrpc_request *req, void *data, int rc)
{
struct ptlrpc_work_async_args *arg = data;

- LASSERT(arg->magic == PTLRPC_WORK_MAGIC);
+ LASSERT(ptlrpcd_check_work(req));
LASSERT(arg->cb != NULL);

- return arg->cb(env, arg->cbdata);
+ rc = arg->cb(env, arg->cbdata);
+
+ list_del_init(&req->rq_set_chain);
+ req->rq_set = NULL;
+
+ if (atomic_dec_return(&req->rq_refcount) > 1) {
+ atomic_set(&req->rq_refcount, 2);
+ ptlrpcd_add_work_req(req);
+ }
+ return rc;
+}
+
+static int worker_format;
+
+static int ptlrpcd_check_work(struct ptlrpc_request *req)
+{
+ return req->rq_pill.rc_fmt == (void *)&worker_format;
}

/**
@@ -3005,6 +3038,7 @@ void *ptlrpcd_alloc_work(struct obd_import *imp,
req->rq_receiving_reply = 0;
req->rq_must_unlink = 0;
req->rq_no_delay = req->rq_no_resend = 1;
+ req->rq_pill.rc_fmt = (void *)&worker_format;

spin_lock_init(&req->rq_lock);
INIT_LIST_HEAD(&req->rq_list);
@@ -3018,7 +3052,6 @@ void *ptlrpcd_alloc_work(struct obd_import *imp,

CLASSERT(sizeof(*args) <= sizeof(req->rq_async_args));
args = ptlrpc_req_async_args(req);
- args->magic = PTLRPC_WORK_MAGIC;
args->cb = cb;
args->cbdata = cbdata;

@@ -3048,25 +3081,8 @@ int ptlrpcd_queue_work(void *handler)
* req as opaque data. - Jinshan
*/
LASSERT(atomic_read(&req->rq_refcount) > 0);
- if (atomic_read(&req->rq_refcount) > 1)
- return -EBUSY;
-
- if (atomic_inc_return(&req->rq_refcount) > 2) { /* race */
- atomic_dec(&req->rq_refcount);
- return -EBUSY;
- }
-
- /* re-initialize the req */
- req->rq_timeout = obd_timeout;
- req->rq_sent = cfs_time_current_sec();
- req->rq_deadline = req->rq_sent + req->rq_timeout;
- req->rq_reply_deadline = req->rq_deadline;
- req->rq_phase = RQ_PHASE_INTERPRET;
- req->rq_next_phase = RQ_PHASE_COMPLETE;
- req->rq_xid = ptlrpc_next_xid();
- req->rq_import_generation = req->rq_import->imp_generation;
-
- ptlrpcd_add_req(req, PDL_POLICY_ROUND, -1);
+ if (atomic_inc_return(&req->rq_refcount) == 2)
+ ptlrpcd_add_work_req(req);
return 0;
}
EXPORT_SYMBOL(ptlrpcd_queue_work);
--
1.8.5.3


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