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Subject[PATCH 5.0 078/117] block: Revert v5.0 blk_mq_request_issue_directly() changes
Date
From: Bart Van Assche <bvanassche@acm.org>

commit fd9c40f64c514bdc585a21e2e33fa5f83ca8811b upstream.

blk_mq_try_issue_directly() can return BLK_STS*_RESOURCE for requests that
have been queued. If that happens when blk_mq_try_issue_directly() is called
by the dm-mpath driver then dm-mpath will try to resubmit a request that is
already queued and a kernel crash follows. Since it is nontrivial to fix
blk_mq_request_issue_directly(), revert the blk_mq_request_issue_directly()
changes that went into kernel v5.0.

This patch reverts the following commits:
* d6a51a97c0b2 ("blk-mq: replace and kill blk_mq_request_issue_directly") # v5.0.
* 5b7a6f128aad ("blk-mq: issue directly with bypass 'false' in blk_mq_sched_insert_requests") # v5.0.
* 7f556a44e61d ("blk-mq: refactor the code of issue request directly") # v5.0.

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Jianchao Wang <jianchao.w.wang@oracle.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: James Smart <james.smart@broadcom.com>
Cc: Dongli Zhang <dongli.zhang@oracle.com>
Cc: Laurence Oberman <loberman@redhat.com>
Cc: <stable@vger.kernel.org>
Reported-by: Laurence Oberman <loberman@redhat.com>
Tested-by: Laurence Oberman <loberman@redhat.com>
Fixes: 7f556a44e61d ("blk-mq: refactor the code of issue request directly") # v5.0.
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
block/blk-core.c | 4 -
block/blk-mq-sched.c | 8 ++-
block/blk-mq.c | 122 ++++++++++++++++++++++++++-------------------------
block/blk-mq.h | 6 --
4 files changed, 71 insertions(+), 69 deletions(-)

--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1246,8 +1246,6 @@ static int blk_cloned_rq_check_limits(st
*/
blk_status_t blk_insert_cloned_request(struct request_queue *q, struct request *rq)
{
- blk_qc_t unused;
-
if (blk_cloned_rq_check_limits(q, rq))
return BLK_STS_IOERR;

@@ -1263,7 +1261,7 @@ blk_status_t blk_insert_cloned_request(s
* bypass a potential scheduler on the bottom device for
* insert.
*/
- return blk_mq_try_issue_directly(rq->mq_hctx, rq, &unused, true, true);
+ return blk_mq_request_issue_directly(rq, true);
}
EXPORT_SYMBOL_GPL(blk_insert_cloned_request);

--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -423,10 +423,12 @@ void blk_mq_sched_insert_requests(struct
* busy in case of 'none' scheduler, and this way may save
* us one extra enqueue & dequeue to sw queue.
*/
- if (!hctx->dispatch_busy && !e && !run_queue_async)
+ if (!hctx->dispatch_busy && !e && !run_queue_async) {
blk_mq_try_issue_list_directly(hctx, list);
- else
- blk_mq_insert_requests(hctx, ctx, list);
+ if (list_empty(list))
+ return;
+ }
+ blk_mq_insert_requests(hctx, ctx, list);
}

blk_mq_run_hw_queue(hctx, run_queue_async);
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1805,74 +1805,76 @@ static blk_status_t __blk_mq_issue_direc
return ret;
}

-blk_status_t blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
+static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
struct request *rq,
blk_qc_t *cookie,
- bool bypass, bool last)
+ bool bypass_insert, bool last)
{
struct request_queue *q = rq->q;
bool run_queue = true;
- blk_status_t ret = BLK_STS_RESOURCE;
- int srcu_idx;
- bool force = false;

- hctx_lock(hctx, &srcu_idx);
/*
- * hctx_lock is needed before checking quiesced flag.
+ * RCU or SRCU read lock is needed before checking quiesced flag.
*
- * When queue is stopped or quiesced, ignore 'bypass', insert
- * and return BLK_STS_OK to caller, and avoid driver to try to
- * dispatch again.
+ * When queue is stopped or quiesced, ignore 'bypass_insert' from
+ * blk_mq_request_issue_directly(), and return BLK_STS_OK to caller,
+ * and avoid driver to try to dispatch again.
*/
- if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q))) {
+ if (blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)) {
run_queue = false;
- bypass = false;
- goto out_unlock;
+ bypass_insert = false;
+ goto insert;
}

- if (unlikely(q->elevator && !bypass))
- goto out_unlock;
+ if (q->elevator && !bypass_insert)
+ goto insert;

if (!blk_mq_get_dispatch_budget(hctx))
- goto out_unlock;
+ goto insert;

if (!blk_mq_get_driver_tag(rq)) {
blk_mq_put_dispatch_budget(hctx);
- goto out_unlock;
+ goto insert;
}

- /*
- * Always add a request that has been through
- *.queue_rq() to the hardware dispatch list.
- */
- force = true;
- ret = __blk_mq_issue_directly(hctx, rq, cookie, last);
-out_unlock:
+ return __blk_mq_issue_directly(hctx, rq, cookie, last);
+insert:
+ if (bypass_insert)
+ return BLK_STS_RESOURCE;
+
+ blk_mq_request_bypass_insert(rq, run_queue);
+ return BLK_STS_OK;
+}
+
+static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
+ struct request *rq, blk_qc_t *cookie)
+{
+ blk_status_t ret;
+ int srcu_idx;
+
+ might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);
+
+ hctx_lock(hctx, &srcu_idx);
+
+ ret = __blk_mq_try_issue_directly(hctx, rq, cookie, false, true);
+ if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE)
+ blk_mq_request_bypass_insert(rq, true);
+ else if (ret != BLK_STS_OK)
+ blk_mq_end_request(rq, ret);
+
+ hctx_unlock(hctx, srcu_idx);
+}
+
+blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last)
+{
+ blk_status_t ret;
+ int srcu_idx;
+ blk_qc_t unused_cookie;
+ struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
+
+ hctx_lock(hctx, &srcu_idx);
+ ret = __blk_mq_try_issue_directly(hctx, rq, &unused_cookie, true, last);
hctx_unlock(hctx, srcu_idx);
- switch (ret) {
- case BLK_STS_OK:
- break;
- case BLK_STS_DEV_RESOURCE:
- case BLK_STS_RESOURCE:
- if (force) {
- blk_mq_request_bypass_insert(rq, run_queue);
- /*
- * We have to return BLK_STS_OK for the DM
- * to avoid livelock. Otherwise, we return
- * the real result to indicate whether the
- * request is direct-issued successfully.
- */
- ret = bypass ? BLK_STS_OK : ret;
- } else if (!bypass) {
- blk_mq_sched_insert_request(rq, false,
- run_queue, false);
- }
- break;
- default:
- if (!bypass)
- blk_mq_end_request(rq, ret);
- break;
- }

return ret;
}
@@ -1880,20 +1882,22 @@ out_unlock:
void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
struct list_head *list)
{
- blk_qc_t unused;
- blk_status_t ret = BLK_STS_OK;
-
while (!list_empty(list)) {
+ blk_status_t ret;
struct request *rq = list_first_entry(list, struct request,
queuelist);

list_del_init(&rq->queuelist);
- if (ret == BLK_STS_OK)
- ret = blk_mq_try_issue_directly(hctx, rq, &unused,
- false,
+ ret = blk_mq_request_issue_directly(rq, list_empty(list));
+ if (ret != BLK_STS_OK) {
+ if (ret == BLK_STS_RESOURCE ||
+ ret == BLK_STS_DEV_RESOURCE) {
+ blk_mq_request_bypass_insert(rq,
list_empty(list));
- else
- blk_mq_sched_insert_request(rq, false, true, false);
+ break;
+ }
+ blk_mq_end_request(rq, ret);
+ }
}

/*
@@ -1901,7 +1905,7 @@ void blk_mq_try_issue_list_directly(stru
* the driver there was more coming, but that turned out to
* be a lie.
*/
- if (ret != BLK_STS_OK && hctx->queue->mq_ops->commit_rqs)
+ if (!list_empty(list) && hctx->queue->mq_ops->commit_rqs)
hctx->queue->mq_ops->commit_rqs(hctx);
}

@@ -2014,13 +2018,13 @@ static blk_qc_t blk_mq_make_request(stru
if (same_queue_rq) {
data.hctx = same_queue_rq->mq_hctx;
blk_mq_try_issue_directly(data.hctx, same_queue_rq,
- &cookie, false, true);
+ &cookie);
}
} else if ((q->nr_hw_queues > 1 && is_sync) || (!q->elevator &&
!data.hctx->dispatch_busy)) {
blk_mq_put_ctx(data.ctx);
blk_mq_bio_to_request(rq, bio);
- blk_mq_try_issue_directly(data.hctx, rq, &cookie, false, true);
+ blk_mq_try_issue_directly(data.hctx, rq, &cookie);
} else {
blk_mq_put_ctx(data.ctx);
blk_mq_bio_to_request(rq, bio);
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -67,10 +67,8 @@ void blk_mq_request_bypass_insert(struct
void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
struct list_head *list);

-blk_status_t blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
- struct request *rq,
- blk_qc_t *cookie,
- bool bypass, bool last);
+/* Used by blk_insert_cloned_request() to issue request directly */
+blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last);
void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
struct list_head *list);


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