[PATCH] block: Submit flush requests to the I/O scheduler

Bart Van Assche
2022-08-12T21:04:09Z

When submitting a REQ_OP_WRITE | REQ_FUA request to a zoned storage
device, these requests must be passed to the (mq-deadline) I/O scheduler
to ensure that these happen at the write pointer. It has been verfied
that this patch prevents that write pointer violations happen
sporadically when f2fs is using a zoned storage device.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
block/blk-mq.c | 31 ++++---------------------------
1 file changed, 4 insertions(+), 27 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 5ee62b95f3e5..530aad95cc33 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2546,16 +2546,14 @@ static blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last)
return __blk_mq_try_issue_directly(rq->mq_hctx, rq, true, last);
}

-static void blk_mq_plug_issue_direct(struct blk_plug *plug, bool from_schedule)
+static void blk_mq_plug_issue(struct blk_plug *plug, bool from_schedule)
{
struct blk_mq_hw_ctx *hctx = NULL;
struct request *rq;
int queued = 0;
- int errors = 0;

while ((rq = rq_list_pop(&plug->mq_list))) {
bool last = rq_list_empty(plug->mq_list);
- blk_status_t ret;

if (hctx != rq->mq_hctx) {
if (hctx)
@@ -2563,29 +2561,9 @@ static void blk_mq_plug_issue_direct(struct blk_plug *plug, bool from_schedule)
hctx = rq->mq_hctx;
}

- ret = blk_mq_request_issue_directly(rq, last);
- switch (ret) {
- case BLK_STS_OK:
- queued++;
- break;
- case BLK_STS_RESOURCE:
- case BLK_STS_DEV_RESOURCE:
- blk_mq_request_bypass_insert(rq, false, last);
- blk_mq_commit_rqs(hctx, &queued, from_schedule);
- return;
- default:
- blk_mq_end_request(rq, ret);
- errors++;
- break;
- }
+ blk_mq_sched_insert_request(rq, /*at_head=*/false,
+ /*run_queue=*/last, /*async=*/false);
}
-
- /*
- * If we didn't flush the entire list, we could have told the driver
- * there was more coming, but that turned out to be a lie.
- */
- if (errors)
- blk_mq_commit_rqs(hctx, &queued, from_schedule);
}

static void __blk_mq_flush_plug_list(struct request_queue *q,
@@ -2655,8 +2633,7 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
return;
}

- blk_mq_run_dispatch_ops(q,
- blk_mq_plug_issue_direct(plug, false));
+ blk_mq_run_dispatch_ops(q, blk_mq_plug_issue(plug, false));
if (rq_list_empty(plug->mq_list))
return;
}