* [PATCH 2/3] block: add a rq_list type
2025-04-18 17:53 [PATCH 0/3] Preserve the request order in the block layer Bart Van Assche
2025-04-18 17:53 ` [PATCH 1/3] block: remove rq_list_move Bart Van Assche
@ 2025-04-18 17:54 ` Bart Van Assche
2025-04-19 11:47 ` Sasha Levin
2025-04-18 17:54 ` [PATCH 3/3] block: don't reorder requests in blk_add_rq_to_plug Bart Van Assche
2025-04-22 11:51 ` [PATCH 0/3] Preserve the request order in the block layer Greg Kroah-Hartman
3 siblings, 1 reply; 9+ messages in thread
From: Bart Van Assche @ 2025-04-18 17:54 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: stable, Christoph Hellwig, Damien Le Moal, Jaegeuk Kim,
Bart Van Assche, Jens Axboe
From: Christoph Hellwig <hch@lst.de>
Upstream commit a3396b99990d8b4e5797e7b16fdeb64c15ae97bb.
Replace the semi-open coded request list helpers with a proper rq_list
type that mirrors the bio_list and has head and tail pointers. Besides
better type safety this actually allows to insert at the tail of the
list, which will be useful soon.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20241113152050.157179-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
block/blk-core.c | 6 +--
block/blk-merge.c | 2 +-
block/blk-mq.c | 40 ++++++++--------
block/blk-mq.h | 2 +-
drivers/block/null_blk/main.c | 9 ++--
drivers/block/virtio_blk.c | 13 +++---
drivers/nvme/host/apple.c | 2 +-
drivers/nvme/host/pci.c | 15 +++---
include/linux/blk-mq.h | 88 +++++++++++++++++++++--------------
include/linux/blkdev.h | 11 +++--
io_uring/rw.c | 4 +-
11 files changed, 104 insertions(+), 88 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 42023addf9cd..c7b6c1f76359 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1121,8 +1121,8 @@ void blk_start_plug_nr_ios(struct blk_plug *plug, unsigned short nr_ios)
return;
plug->cur_ktime = 0;
- plug->mq_list = NULL;
- plug->cached_rq = NULL;
+ rq_list_init(&plug->mq_list);
+ rq_list_init(&plug->cached_rqs);
plug->nr_ios = min_t(unsigned short, nr_ios, BLK_MAX_REQUEST_COUNT);
plug->rq_count = 0;
plug->multiple_queues = false;
@@ -1218,7 +1218,7 @@ void __blk_flush_plug(struct blk_plug *plug, bool from_schedule)
* queue for cached requests, we don't want a blocked task holding
* up a queue freeze/quiesce event.
*/
- if (unlikely(!rq_list_empty(plug->cached_rq)))
+ if (unlikely(!rq_list_empty(&plug->cached_rqs)))
blk_mq_free_plug_rqs(plug);
plug->cur_ktime = 0;
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 5baa950f34fe..ceac64e796ea 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -1175,7 +1175,7 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
struct blk_plug *plug = current->plug;
struct request *rq;
- if (!plug || rq_list_empty(plug->mq_list))
+ if (!plug || rq_list_empty(&plug->mq_list))
return false;
rq_list_for_each(&plug->mq_list, rq) {
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 662e52ab0646..c7fb3722d620 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -506,7 +506,7 @@ __blk_mq_alloc_requests_batch(struct blk_mq_alloc_data *data)
prefetch(tags->static_rqs[tag]);
tag_mask &= ~(1UL << i);
rq = blk_mq_rq_ctx_init(data, tags, tag);
- rq_list_add(data->cached_rq, rq);
+ rq_list_add_head(data->cached_rqs, rq);
nr++;
}
if (!(data->rq_flags & RQF_SCHED_TAGS))
@@ -515,7 +515,7 @@ __blk_mq_alloc_requests_batch(struct blk_mq_alloc_data *data)
percpu_ref_get_many(&data->q->q_usage_counter, nr - 1);
data->nr_tags -= nr;
- return rq_list_pop(data->cached_rq);
+ return rq_list_pop(data->cached_rqs);
}
static struct request *__blk_mq_alloc_requests(struct blk_mq_alloc_data *data)
@@ -612,7 +612,7 @@ static struct request *blk_mq_rq_cache_fill(struct request_queue *q,
.flags = flags,
.cmd_flags = opf,
.nr_tags = plug->nr_ios,
- .cached_rq = &plug->cached_rq,
+ .cached_rqs = &plug->cached_rqs,
};
struct request *rq;
@@ -637,14 +637,14 @@ static struct request *blk_mq_alloc_cached_request(struct request_queue *q,
if (!plug)
return NULL;
- if (rq_list_empty(plug->cached_rq)) {
+ if (rq_list_empty(&plug->cached_rqs)) {
if (plug->nr_ios == 1)
return NULL;
rq = blk_mq_rq_cache_fill(q, plug, opf, flags);
if (!rq)
return NULL;
} else {
- rq = rq_list_peek(&plug->cached_rq);
+ rq = rq_list_peek(&plug->cached_rqs);
if (!rq || rq->q != q)
return NULL;
@@ -653,7 +653,7 @@ static struct request *blk_mq_alloc_cached_request(struct request_queue *q,
if (op_is_flush(rq->cmd_flags) != op_is_flush(opf))
return NULL;
- plug->cached_rq = rq_list_next(rq);
+ rq_list_pop(&plug->cached_rqs);
blk_mq_rq_time_init(rq, 0);
}
@@ -830,7 +830,7 @@ void blk_mq_free_plug_rqs(struct blk_plug *plug)
{
struct request *rq;
- while ((rq = rq_list_pop(&plug->cached_rq)) != NULL)
+ while ((rq = rq_list_pop(&plug->cached_rqs)) != NULL)
blk_mq_free_request(rq);
}
@@ -1386,8 +1386,7 @@ static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
*/
if (!plug->has_elevator && (rq->rq_flags & RQF_SCHED_TAGS))
plug->has_elevator = true;
- rq->rq_next = NULL;
- rq_list_add(&plug->mq_list, rq);
+ rq_list_add_head(&plug->mq_list, rq);
plug->rq_count++;
}
@@ -2781,7 +2780,7 @@ static void blk_mq_plug_issue_direct(struct blk_plug *plug)
blk_status_t ret = BLK_STS_OK;
while ((rq = rq_list_pop(&plug->mq_list))) {
- bool last = rq_list_empty(plug->mq_list);
+ bool last = rq_list_empty(&plug->mq_list);
if (hctx != rq->mq_hctx) {
if (hctx) {
@@ -2824,8 +2823,7 @@ static void blk_mq_dispatch_plug_list(struct blk_plug *plug, bool from_sched)
{
struct blk_mq_hw_ctx *this_hctx = NULL;
struct blk_mq_ctx *this_ctx = NULL;
- struct request *requeue_list = NULL;
- struct request **requeue_lastp = &requeue_list;
+ struct rq_list requeue_list = {};
unsigned int depth = 0;
bool is_passthrough = false;
LIST_HEAD(list);
@@ -2839,12 +2837,12 @@ static void blk_mq_dispatch_plug_list(struct blk_plug *plug, bool from_sched)
is_passthrough = blk_rq_is_passthrough(rq);
} else if (this_hctx != rq->mq_hctx || this_ctx != rq->mq_ctx ||
is_passthrough != blk_rq_is_passthrough(rq)) {
- rq_list_add_tail(&requeue_lastp, rq);
+ rq_list_add_tail(&requeue_list, rq);
continue;
}
list_add(&rq->queuelist, &list);
depth++;
- } while (!rq_list_empty(plug->mq_list));
+ } while (!rq_list_empty(&plug->mq_list));
plug->mq_list = requeue_list;
trace_block_unplug(this_hctx->queue, depth, !from_sched);
@@ -2899,19 +2897,19 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
if (q->mq_ops->queue_rqs) {
blk_mq_run_dispatch_ops(q,
__blk_mq_flush_plug_list(q, plug));
- if (rq_list_empty(plug->mq_list))
+ if (rq_list_empty(&plug->mq_list))
return;
}
blk_mq_run_dispatch_ops(q,
blk_mq_plug_issue_direct(plug));
- if (rq_list_empty(plug->mq_list))
+ if (rq_list_empty(&plug->mq_list))
return;
}
do {
blk_mq_dispatch_plug_list(plug, from_schedule);
- } while (!rq_list_empty(plug->mq_list));
+ } while (!rq_list_empty(&plug->mq_list));
}
static void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
@@ -2976,7 +2974,7 @@ static struct request *blk_mq_get_new_requests(struct request_queue *q,
if (plug) {
data.nr_tags = plug->nr_ios;
plug->nr_ios = 1;
- data.cached_rq = &plug->cached_rq;
+ data.cached_rqs = &plug->cached_rqs;
}
rq = __blk_mq_alloc_requests(&data);
@@ -2999,7 +2997,7 @@ static struct request *blk_mq_peek_cached_request(struct blk_plug *plug,
if (!plug)
return NULL;
- rq = rq_list_peek(&plug->cached_rq);
+ rq = rq_list_peek(&plug->cached_rqs);
if (!rq || rq->q != q)
return NULL;
if (type != rq->mq_hctx->type &&
@@ -3013,14 +3011,14 @@ static struct request *blk_mq_peek_cached_request(struct blk_plug *plug,
static void blk_mq_use_cached_rq(struct request *rq, struct blk_plug *plug,
struct bio *bio)
{
- WARN_ON_ONCE(rq_list_peek(&plug->cached_rq) != rq);
+ if (rq_list_pop(&plug->cached_rqs) != rq)
+ WARN_ON_ONCE(1);
/*
* If any qos ->throttle() end up blocking, we will have flushed the
* plug and hence killed the cached_rq list as well. Pop this entry
* before we throttle.
*/
- plug->cached_rq = rq_list_next(rq);
rq_qos_throttle(rq->q, bio);
blk_mq_rq_time_init(rq, 0);
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 364c0415293c..a80d3b3105f9 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -155,7 +155,7 @@ struct blk_mq_alloc_data {
/* allocate multiple requests/tags in one go */
unsigned int nr_tags;
- struct request **cached_rq;
+ struct rq_list *cached_rqs;
/* input & output parameter */
struct blk_mq_ctx *ctx;
diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index c479348ce8ff..f10369ad90f7 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -1638,10 +1638,9 @@ static blk_status_t null_queue_rq(struct blk_mq_hw_ctx *hctx,
return BLK_STS_OK;
}
-static void null_queue_rqs(struct request **rqlist)
+static void null_queue_rqs(struct rq_list *rqlist)
{
- struct request *requeue_list = NULL;
- struct request **requeue_lastp = &requeue_list;
+ struct rq_list requeue_list = {};
struct blk_mq_queue_data bd = { };
blk_status_t ret;
@@ -1651,8 +1650,8 @@ static void null_queue_rqs(struct request **rqlist)
bd.rq = rq;
ret = null_queue_rq(rq->mq_hctx, &bd);
if (ret != BLK_STS_OK)
- rq_list_add_tail(&requeue_lastp, rq);
- } while (!rq_list_empty(*rqlist));
+ rq_list_add_tail(&requeue_list, rq);
+ } while (!rq_list_empty(rqlist));
*rqlist = requeue_list;
}
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 44a6937a4b65..2069bf9701f5 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -472,7 +472,7 @@ static bool virtblk_prep_rq_batch(struct request *req)
}
static void virtblk_add_req_batch(struct virtio_blk_vq *vq,
- struct request **rqlist)
+ struct rq_list *rqlist)
{
struct request *req;
unsigned long flags;
@@ -499,11 +499,10 @@ static void virtblk_add_req_batch(struct virtio_blk_vq *vq,
virtqueue_notify(vq->vq);
}
-static void virtio_queue_rqs(struct request **rqlist)
+static void virtio_queue_rqs(struct rq_list *rqlist)
{
- struct request *submit_list = NULL;
- struct request *requeue_list = NULL;
- struct request **requeue_lastp = &requeue_list;
+ struct rq_list submit_list = { };
+ struct rq_list requeue_list = { };
struct virtio_blk_vq *vq = NULL;
struct request *req;
@@ -515,9 +514,9 @@ static void virtio_queue_rqs(struct request **rqlist)
vq = this_vq;
if (virtblk_prep_rq_batch(req))
- rq_list_add(&submit_list, req); /* reverse order */
+ rq_list_add_head(&submit_list, req); /* reverse order */
else
- rq_list_add_tail(&requeue_lastp, req);
+ rq_list_add_tail(&requeue_list, req);
}
if (vq)
diff --git a/drivers/nvme/host/apple.c b/drivers/nvme/host/apple.c
index e79a0adf1395..328f5a103628 100644
--- a/drivers/nvme/host/apple.c
+++ b/drivers/nvme/host/apple.c
@@ -650,7 +650,7 @@ static bool apple_nvme_handle_cq(struct apple_nvme_queue *q, bool force)
found = apple_nvme_poll_cq(q, &iob);
- if (!rq_list_empty(iob.req_list))
+ if (!rq_list_empty(&iob.req_list))
apple_nvme_complete_batch(&iob);
return found;
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index af45a1b865ee..e943c1be0fca 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -985,7 +985,7 @@ static blk_status_t nvme_queue_rq(struct blk_mq_hw_ctx *hctx,
return BLK_STS_OK;
}
-static void nvme_submit_cmds(struct nvme_queue *nvmeq, struct request **rqlist)
+static void nvme_submit_cmds(struct nvme_queue *nvmeq, struct rq_list *rqlist)
{
struct request *req;
@@ -1013,11 +1013,10 @@ static bool nvme_prep_rq_batch(struct nvme_queue *nvmeq, struct request *req)
return nvme_prep_rq(nvmeq->dev, req) == BLK_STS_OK;
}
-static void nvme_queue_rqs(struct request **rqlist)
+static void nvme_queue_rqs(struct rq_list *rqlist)
{
- struct request *submit_list = NULL;
- struct request *requeue_list = NULL;
- struct request **requeue_lastp = &requeue_list;
+ struct rq_list submit_list = { };
+ struct rq_list requeue_list = { };
struct nvme_queue *nvmeq = NULL;
struct request *req;
@@ -1027,9 +1026,9 @@ static void nvme_queue_rqs(struct request **rqlist)
nvmeq = req->mq_hctx->driver_data;
if (nvme_prep_rq_batch(nvmeq, req))
- rq_list_add(&submit_list, req); /* reverse order */
+ rq_list_add_head(&submit_list, req); /* reverse order */
else
- rq_list_add_tail(&requeue_lastp, req);
+ rq_list_add_tail(&requeue_list, req);
}
if (nvmeq)
@@ -1176,7 +1175,7 @@ static irqreturn_t nvme_irq(int irq, void *data)
DEFINE_IO_COMP_BATCH(iob);
if (nvme_poll_cq(nvmeq, &iob)) {
- if (!rq_list_empty(iob.req_list))
+ if (!rq_list_empty(&iob.req_list))
nvme_pci_complete_batch(&iob);
return IRQ_HANDLED;
}
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index cd04e71ecb88..b160d131204e 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -230,44 +230,60 @@ static inline unsigned short req_get_ioprio(struct request *req)
#define rq_dma_dir(rq) \
(op_is_write(req_op(rq)) ? DMA_TO_DEVICE : DMA_FROM_DEVICE)
-#define rq_list_add(listptr, rq) do { \
- (rq)->rq_next = *(listptr); \
- *(listptr) = rq; \
-} while (0)
-
-#define rq_list_add_tail(lastpptr, rq) do { \
- (rq)->rq_next = NULL; \
- **(lastpptr) = rq; \
- *(lastpptr) = &rq->rq_next; \
-} while (0)
-
-#define rq_list_pop(listptr) \
-({ \
- struct request *__req = NULL; \
- if ((listptr) && *(listptr)) { \
- __req = *(listptr); \
- *(listptr) = __req->rq_next; \
- } \
- __req; \
-})
+static inline int rq_list_empty(const struct rq_list *rl)
+{
+ return rl->head == NULL;
+}
-#define rq_list_peek(listptr) \
-({ \
- struct request *__req = NULL; \
- if ((listptr) && *(listptr)) \
- __req = *(listptr); \
- __req; \
-})
+static inline void rq_list_init(struct rq_list *rl)
+{
+ rl->head = NULL;
+ rl->tail = NULL;
+}
+
+static inline void rq_list_add_tail(struct rq_list *rl, struct request *rq)
+{
+ rq->rq_next = NULL;
+ if (rl->tail)
+ rl->tail->rq_next = rq;
+ else
+ rl->head = rq;
+ rl->tail = rq;
+}
+
+static inline void rq_list_add_head(struct rq_list *rl, struct request *rq)
+{
+ rq->rq_next = rl->head;
+ rl->head = rq;
+ if (!rl->tail)
+ rl->tail = rq;
+}
+
+static inline struct request *rq_list_pop(struct rq_list *rl)
+{
+ struct request *rq = rl->head;
+
+ if (rq) {
+ rl->head = rl->head->rq_next;
+ if (!rl->head)
+ rl->tail = NULL;
+ rq->rq_next = NULL;
+ }
+
+ return rq;
+}
-#define rq_list_for_each(listptr, pos) \
- for (pos = rq_list_peek((listptr)); pos; pos = rq_list_next(pos))
+static inline struct request *rq_list_peek(struct rq_list *rl)
+{
+ return rl->head;
+}
-#define rq_list_for_each_safe(listptr, pos, nxt) \
- for (pos = rq_list_peek((listptr)), nxt = rq_list_next(pos); \
- pos; pos = nxt, nxt = pos ? rq_list_next(pos) : NULL)
+#define rq_list_for_each(rl, pos) \
+ for (pos = rq_list_peek((rl)); (pos); pos = pos->rq_next)
-#define rq_list_next(rq) (rq)->rq_next
-#define rq_list_empty(list) ((list) == (struct request *) NULL)
+#define rq_list_for_each_safe(rl, pos, nxt) \
+ for (pos = rq_list_peek((rl)), nxt = pos->rq_next; \
+ pos; pos = nxt, nxt = pos ? pos->rq_next : NULL)
/**
* enum blk_eh_timer_return - How the timeout handler should proceed
@@ -560,7 +576,7 @@ struct blk_mq_ops {
* empty the @rqlist completely, then the rest will be queued
* individually by the block layer upon return.
*/
- void (*queue_rqs)(struct request **rqlist);
+ void (*queue_rqs)(struct rq_list *rqlist);
/**
* @get_budget: Reserve budget before queue request, once .queue_rq is
@@ -893,7 +909,7 @@ static inline bool blk_mq_add_to_batch(struct request *req,
else if (iob->complete != complete)
return false;
iob->need_ts |= blk_mq_need_time_stamp(req);
- rq_list_add(&iob->req_list, req);
+ rq_list_add_head(&iob->req_list, req);
return true;
}
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 8f37c5dd52b2..402a7d7fe98d 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -996,6 +996,11 @@ extern void blk_put_queue(struct request_queue *);
void blk_mark_disk_dead(struct gendisk *disk);
#ifdef CONFIG_BLOCK
+struct rq_list {
+ struct request *head;
+ struct request *tail;
+};
+
/*
* blk_plug permits building a queue of related requests by holding the I/O
* fragments for a short period. This allows merging of sequential requests
@@ -1008,10 +1013,10 @@ void blk_mark_disk_dead(struct gendisk *disk);
* blk_flush_plug() is called.
*/
struct blk_plug {
- struct request *mq_list; /* blk-mq requests */
+ struct rq_list mq_list; /* blk-mq requests */
/* if ios_left is > 1, we can batch tag/rq allocations */
- struct request *cached_rq;
+ struct rq_list cached_rqs;
u64 cur_ktime;
unsigned short nr_ios;
@@ -1660,7 +1665,7 @@ int bdev_thaw(struct block_device *bdev);
void bdev_fput(struct file *bdev_file);
struct io_comp_batch {
- struct request *req_list;
+ struct rq_list req_list;
bool need_ts;
void (*complete)(struct io_comp_batch *);
};
diff --git a/io_uring/rw.c b/io_uring/rw.c
index 6abc495602a4..a1ed64760eba 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -1190,12 +1190,12 @@ int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin)
poll_flags |= BLK_POLL_ONESHOT;
/* iopoll may have completed current req */
- if (!rq_list_empty(iob.req_list) ||
+ if (!rq_list_empty(&iob.req_list) ||
READ_ONCE(req->iopoll_completed))
break;
}
- if (!rq_list_empty(iob.req_list))
+ if (!rq_list_empty(&iob.req_list))
iob.complete(&iob);
else if (!pos)
return 0;
^ permalink raw reply related [flat|nested] 9+ messages in thread