[PATCH v3 09/17] scsi-multipath: add scsi_mpath_{start,end}_request()
John Garry
john.g.garry at oracle.com
Fri Jul 3 03:33:54 PDT 2026
Add scsi_mpath_{start,end}_request() to handle updating private multipath
request data, like nvme_mpath_{start,end}_request().
New member Scsi_Host.mpath_nr_active is added. This is required for queue
depth multipath iopolicy.
For NVMe, this count is per controller. The reason is that many NSes may
be connected to a controller, so congestion should be judged at
controller level.
SCSI has no definition of a controller, but SCSI host is a comparable
concept.
Indeed, many SCSI disks may be connected to the same SCSI host, so it
makes sense to count number of active requests at this point. However,
for a transport like iSCSI Initiator over TCP/IP, we have a separate SCSI
host per SCSI device (so there the count would be same at SCSI device
level).
Signed-off-by: John Garry <john.g.garry at oracle.com>
---
drivers/scsi/scsi_lib.c | 6 +++++
drivers/scsi/scsi_multipath.c | 51 +++++++++++++++++++++++++++++++++++
include/scsi/scsi_cmnd.h | 5 ++++
include/scsi/scsi_host.h | 4 +++
include/scsi/scsi_multipath.h | 8 ++++++
5 files changed, 74 insertions(+)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index cc34253c467a2..f8b389fda2537 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -669,6 +669,9 @@ static bool scsi_end_request(struct request *req, blk_status_t error,
struct scsi_device *sdev = cmd->device;
struct request_queue *q = sdev->request_queue;
+ if (is_mpath_request(req))
+ scsi_mpath_end_request(req);
+
if (blk_update_request(req, error, bytes))
return true;
@@ -1917,6 +1920,9 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
memset(cmd->sense_buffer, 0, SCSI_SENSE_BUFFERSIZE);
cmd->submitter = SUBMITTED_BY_BLOCK_LAYER;
+ if (is_mpath_request(req))
+ scsi_mpath_start_request(req);
+
blk_mq_start_request(req);
if (blk_mq_is_reserved_rq(req)) {
reason = shost->hostt->queue_reserved_command(shost, cmd);
diff --git a/drivers/scsi/scsi_multipath.c b/drivers/scsi/scsi_multipath.c
index d8ea9ffe8942c..61fa2e4cdfdab 100644
--- a/drivers/scsi/scsi_multipath.c
+++ b/drivers/scsi/scsi_multipath.c
@@ -543,6 +543,57 @@ void scsi_mpath_put_head(struct scsi_mpath_head *scsi_mpath_head)
}
EXPORT_SYMBOL_GPL(scsi_mpath_put_head);
+void scsi_mpath_start_request(struct request *req)
+{
+ struct scsi_cmnd *scmd = blk_mq_rq_to_pdu(req);
+ struct scsi_device *sdev = scmd->device;
+ struct scsi_mpath_device *scsi_mpath_dev = sdev->scsi_mpath_dev;
+ struct scsi_mpath_head *scsi_mpath_head =
+ scsi_mpath_dev->scsi_mpath_head;
+ struct mpath_head *mpath_head = &scsi_mpath_head->mpath_head;
+ struct gendisk *disk = mpath_head->disk;
+
+ if (mpath_qd_iopolicy(&scsi_mpath_head->iopolicy) &&
+ !(scmd->flags & SCMD_MPATH_CNT_ACTIVE)) {
+ struct Scsi_Host *shost = sdev->host;
+
+ atomic_inc(&shost->mpath_nr_active);
+ scmd->flags |= SCMD_MPATH_CNT_ACTIVE;
+ }
+
+ if (!blk_queue_io_stat(disk->queue) || blk_rq_is_passthrough(req) ||
+ (scmd->flags & SCMD_MPATH_IO_STATS))
+ return;
+
+ scmd->flags |= SCMD_MPATH_IO_STATS;
+ scmd->start_time = bdev_start_io_acct(disk->part0, req_op(req),
+ jiffies);
+}
+
+void scsi_mpath_end_request(struct request *req)
+{
+ struct scsi_cmnd *scmd = blk_mq_rq_to_pdu(req);
+ struct scsi_device *sdev = scmd->device;
+ struct scsi_mpath_device *scsi_mpath_dev =
+ sdev->scsi_mpath_dev;
+ struct scsi_mpath_head *scsi_mpath_head =
+ scsi_mpath_dev->scsi_mpath_head;
+ struct mpath_head *mpath_head = &scsi_mpath_head->mpath_head;
+ struct gendisk *disk = mpath_head->disk;
+
+ if (scmd->flags & SCMD_MPATH_CNT_ACTIVE) {
+ struct Scsi_Host *shost = sdev->host;
+
+ atomic_dec_if_positive(&shost->mpath_nr_active);
+ }
+
+ if (!(scmd->flags & SCMD_MPATH_IO_STATS))
+ return;
+ bdev_end_io_acct(disk->part0, req_op(req),
+ blk_rq_bytes(req) >> SECTOR_SHIFT,
+ scmd->start_time);
+}
+
int __init scsi_multipath_init(void)
{
return class_register(&scsi_mpath_device_class);
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index 8ecfb94049db5..c6571a36e577b 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -60,6 +60,8 @@ struct scsi_pointer {
#define SCMD_FAIL_IF_RECOVERING (1 << 4)
/* flags preserved across unprep / reprep */
#define SCMD_PRESERVED_FLAGS (SCMD_INITIALIZED | SCMD_FAIL_IF_RECOVERING)
+#define SCMD_MPATH_IO_STATS (1 << 5)
+#define SCMD_MPATH_CNT_ACTIVE (1 << 6)
/* for scmd->state */
#define SCMD_STATE_COMPLETE 0
@@ -139,6 +141,9 @@ struct scsi_cmnd {
* to release this memory. (The memory
* obtained by scsi_malloc is guaranteed
* to be at an address < 16Mb). */
+ #ifdef CONFIG_SCSI_MULTIPATH
+ unsigned long start_time;
+ #endif
int result; /* Status code from lower level driver */
};
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 7e2011830ba4b..cf4fff3ea1a8e 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -753,6 +753,10 @@ struct Scsi_Host {
/* Delay for runtime autosuspend */
int rpm_autosuspend_delay;
+ #ifdef CONFIG_SCSI_MULTIPATH
+ atomic_t mpath_nr_active;
+ #endif
+
/*
* We should ensure that this is aligned, both for better performance
* and also because some compilers (m68k) don't automatically force
diff --git a/include/scsi/scsi_multipath.h b/include/scsi/scsi_multipath.h
index d8644d6261992..ed5c77d568843 100644
--- a/include/scsi/scsi_multipath.h
+++ b/include/scsi/scsi_multipath.h
@@ -55,6 +55,8 @@ void scsi_mpath_add_sysfs_link(struct scsi_device *sdev);
void scsi_mpath_remove_sysfs_link(struct scsi_device *sdev);
int scsi_mpath_get_head(struct scsi_mpath_head *scsi_mpath_head);
void scsi_mpath_put_head(struct scsi_mpath_head *scsi_mpath_head);
+void scsi_mpath_start_request(struct request *req);
+void scsi_mpath_end_request(struct request *req);
#else /* CONFIG_SCSI_MULTIPATH */
struct scsi_mpath_head {
@@ -93,6 +95,12 @@ static inline
void scsi_mpath_put_head(struct scsi_mpath_head *scsi_mpath_head)
{
}
+static inline void scsi_mpath_start_request(struct request *req)
+{
+}
+static inline void scsi_mpath_end_request(struct request *req)
+{
+}
static inline void scsi_mpath_add_sysfs_link(struct scsi_device *sdev)
{
}
--
2.43.7
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