[PATCH 03/24] scsi-multipath: introduce scsi_device head structure
Hannes Reinecke
hare at suse.com
Mon Mar 2 23:13:27 PST 2026
On 2/25/26 16:36, John Garry wrote:
> Introduce a scsi_device head structure - scsi_mpath_head - to manage
> multipathing for a scsi_device. This is similar to nvme_ns_head structure.
>
> There is no reference in scsi_mpath_head to any disk, as this would be
> mananged by the scsi_disk driver.
>
> A list of scsi_mpath_head structures is managed to lookup for matching
> multipathed scsi_device's. Matching is done through the scsi_device
> unique id.
>
> Signed-off-by: John Garry <john.g.garry at oracle.com>
> ---
> drivers/scsi/scsi_multipath.c | 147 ++++++++++++++++++++++++++++++++++
> drivers/scsi/scsi_sysfs.c | 3 +
> include/scsi/scsi_multipath.h | 29 +++++++
> 3 files changed, 179 insertions(+)
>
> diff --git a/drivers/scsi/scsi_multipath.c b/drivers/scsi/scsi_multipath.c
> index 04e0bad3d9204..49316269fad8e 100644
> --- a/drivers/scsi/scsi_multipath.c
> +++ b/drivers/scsi/scsi_multipath.c
> @@ -16,6 +16,10 @@
> bool scsi_multipath;
> static bool scsi_multipath_always;
>
> +static LIST_HEAD(scsi_mpath_heads_list);
> +static DEFINE_MUTEX(scsi_mpath_heads_lock);
> +static DEFINE_IDA(scsi_multipath_dev_ida);
> +
> static int multipath_param_set(const char *val, const struct kernel_param *kp)
> {
> int ret;
> @@ -99,6 +103,73 @@ static int scsi_multipath_sdev_init(struct scsi_device *sdev)
> return 0;
> }
>
> +struct mpath_head_template smpdt_pr = {
> +};
> +
> +static struct scsi_mpath_head *scsi_mpath_alloc_head(void)
> +{
> + struct scsi_mpath_head *scsi_mpath_head;
> + int ret;
> +
> + scsi_mpath_head = kzalloc(sizeof(*scsi_mpath_head), GFP_KERNEL);
> + if (!scsi_mpath_head)
> + return NULL;
> +
> + ida_init(&scsi_mpath_head->ida);
> + mutex_init(&scsi_mpath_head->lock);
> +
> + scsi_mpath_head->mpath_head = mpath_alloc_head();
> + if (IS_ERR(scsi_mpath_head->mpath_head))
> + goto out_free;
> + scsi_mpath_head->mpath_head->mpdt = &smpdt_pr;
mpdt?
What's that supposed to mean?
Seems to be like a persistent reservation thing, so why don't
you introduce it together with PR suppoer?
> + scsi_mpath_head->mpath_head->drvdata = scsi_mpath_head;
> +
> + scsi_mpath_head->index = ida_alloc(&scsi_multipath_dev_ida, GFP_KERNEL);
> + if (scsi_mpath_head->index < 0)
> + goto out_put_head;
> +
> + device_initialize(&scsi_mpath_head->dev);
> + ret = dev_set_name(&scsi_mpath_head->dev, "%d", scsi_mpath_head->index);
Huh? The name is just the number? So we will have a device
/sys/devices/virtual/1 ?
The sysfs registration looks decidedly odd.
I guess we should add a scsi multipath class to sort the devices under.
> + if (ret) {
> + put_device(&scsi_mpath_head->dev);
> + goto out_free_ida;
> + }
> +
> + return scsi_mpath_head;
> +
> +out_free_ida:
> + ida_free(&scsi_multipath_dev_ida, scsi_mpath_head->index);
> +out_put_head:
> + mpath_put_head(scsi_mpath_head->mpath_head);
> +out_free:
> + kfree(scsi_mpath_head);
> + return NULL;
> +}
> +
> +static struct scsi_mpath_head *scsi_mpath_find_head(
> + struct scsi_mpath_device *scsi_mpath_dev)
> +{
> + struct scsi_mpath_head *scsi_mpath_head;
> + int ret;
> +
> + mutex_lock(&scsi_mpath_heads_lock);
> + list_for_each_entry(scsi_mpath_head, &scsi_mpath_heads_list, entry) {
> + ret = scsi_mpath_get_head(scsi_mpath_head);
> + if (ret)
> + continue;
> + if (strncmp(scsi_mpath_head->wwid,
> + scsi_mpath_dev->device_id_str,
> + SCSI_MPATH_DEVICE_ID_LEN) == 0) {
> +
> + mutex_unlock(&scsi_mpath_heads_lock);
> + return scsi_mpath_head;
> + }
> + scsi_mpath_put_head(scsi_mpath_head);
> + }
> +
> + return NULL;
> +}
> +
> static void scsi_multipath_sdev_uninit(struct scsi_device *sdev)
> {
> kfree(sdev->scsi_mpath_dev);
> @@ -107,6 +178,7 @@ static void scsi_multipath_sdev_uninit(struct scsi_device *sdev)
>
> int scsi_mpath_dev_alloc(struct scsi_device *sdev)
> {
> + struct scsi_mpath_head *scsi_mpath_head;
> int ret;
>
> if (!scsi_multipath)
> @@ -127,13 +199,75 @@ int scsi_mpath_dev_alloc(struct scsi_device *sdev)
> goto out_uninit;
> }
>
> + scsi_mpath_head = scsi_mpath_find_head(sdev->scsi_mpath_dev);
> + if (scsi_mpath_head)
> + goto found;
> + /* scsi_mpath_disks_list lock held */
> + scsi_mpath_head = scsi_mpath_alloc_head();
> + if (!scsi_mpath_head)
> + goto out_uninit;
> +
> + strcpy(scsi_mpath_head->wwid, sdev->scsi_mpath_dev->device_id_str);
> +
Do we have a sysfs attribute for this?
> + ret = device_add(&scsi_mpath_head->dev);
> + if (ret)
> + goto out_put_head;
> +
> + list_add_tail(&scsi_mpath_head->entry, &scsi_mpath_heads_list);
> +
> + mutex_unlock(&scsi_mpath_heads_lock);
> + sdev->scsi_mpath_dev->scsi_mpath_head = scsi_mpath_head;
> +
> +found:
> + sdev->scsi_mpath_dev->index = ida_alloc(&scsi_mpath_head->ida, GFP_KERNEL);
> + if (sdev->scsi_mpath_dev->index < 0) {
> + ret = sdev->scsi_mpath_dev->index;
> + goto out_put_head;
> + }
> +
> + mutex_lock(&scsi_mpath_head->lock);
> + scsi_mpath_head->dev_count++;
> + mutex_unlock(&scsi_mpath_head->lock);
> +
> + sdev->scsi_mpath_dev->scsi_mpath_head = scsi_mpath_head;
> return 0;
>
> +out_put_head:
> + scsi_mpath_put_head(scsi_mpath_head);
> out_uninit:
> + mutex_unlock(&scsi_mpath_heads_lock);
> scsi_multipath_sdev_uninit(sdev);
> return ret;
> }
>
> +static void scsi_mpath_remove_head(struct scsi_mpath_device *scsi_mpath_dev)
> +{
> + struct scsi_mpath_head *scsi_mpath_head =
> + scsi_mpath_dev->scsi_mpath_head;
> + bool last_path = false;
> +
> + mutex_lock(&scsi_mpath_head->lock);
> + scsi_mpath_head->dev_count--;
> + if (scsi_mpath_head->dev_count == 0)
> + last_path = true;
> + mutex_unlock(&scsi_mpath_head->lock);
> +
> + if (last_path)
> + device_del(&scsi_mpath_head->dev);
> +
> + scsi_mpath_dev->scsi_mpath_head = NULL;
> + scsi_mpath_put_head(scsi_mpath_head);
> +}
> +
> +void scsi_mpath_remove_device(struct scsi_mpath_device *scsi_mpath_dev)
> +{
> + struct scsi_mpath_head *scsi_mpath_head = scsi_mpath_dev->scsi_mpath_head;
> +
> + ida_free(&scsi_mpath_head->ida, scsi_mpath_dev->index);
> +
> + scsi_mpath_remove_head(scsi_mpath_dev);
> +}
> +
> void scsi_mpath_dev_release(struct scsi_device *sdev)
> {
> struct scsi_mpath_device *scsi_mpath_dev = sdev->scsi_mpath_dev;
> @@ -142,8 +276,21 @@ void scsi_mpath_dev_release(struct scsi_device *sdev)
> return;
>
> scsi_multipath_sdev_uninit(sdev);
> +}
> +
> +int scsi_mpath_get_head(struct scsi_mpath_head *scsi_mpath_head)
> +{
> + if (!get_device(&scsi_mpath_head->dev))
> + return -ENXIO;
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(scsi_mpath_get_head);
>
> +void scsi_mpath_put_head(struct scsi_mpath_head *scsi_mpath_head)
> +{
> + put_device(&scsi_mpath_head->dev);
> }
> +EXPORT_SYMBOL_GPL(scsi_mpath_put_head);
>
> int __init scsi_multipath_init(void)
> {
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index 0d69e27600a7a..287a683e89ae5 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -1447,6 +1447,9 @@ void __scsi_remove_device(struct scsi_device *sdev)
> } else
> put_device(&sdev->sdev_dev);
>
> + if (sdev->scsi_mpath_dev)
> + scsi_mpath_remove_device(sdev->scsi_mpath_dev);
> +
> /*
> * Stop accepting new requests and wait until all queuecommand() and
> * scsi_run_queue() invocations have finished before tearing down the
> diff --git a/include/scsi/scsi_multipath.h b/include/scsi/scsi_multipath.h
> index ca00ea10cd5db..38953b05a44dc 100644
> --- a/include/scsi/scsi_multipath.h
> +++ b/include/scsi/scsi_multipath.h
> @@ -19,9 +19,22 @@
> #ifdef CONFIG_SCSI_MULTIPATH
> #define SCSI_MPATH_DEVICE_ID_LEN 40
>
> +struct scsi_mpath_head {
> + char wwid[SCSI_MPATH_DEVICE_ID_LEN];
Don't name it WWID. That's an ATA thing. Make it vpd_id.
> + struct list_head entry;
> + int dev_count;
> + struct ida ida;
> + struct mutex lock;
> + struct mpath_head *mpath_head;
> + struct device dev;
> + int index;
> +};
> +
> struct scsi_mpath_device {
> struct mpath_device mpath_device;
> struct scsi_device *sdev;
> + int index;
> + struct scsi_mpath_head *scsi_mpath_head;
>
> char device_id_str[SCSI_MPATH_DEVICE_ID_LEN];
> };
> @@ -32,8 +45,13 @@ int scsi_mpath_dev_alloc(struct scsi_device *sdev);
> void scsi_mpath_dev_release(struct scsi_device *sdev);
> int scsi_multipath_init(void);
> void scsi_multipath_exit(void);
> +void scsi_mpath_remove_device(struct scsi_mpath_device *scsi_mpath_dev);
> +int scsi_mpath_get_head(struct scsi_mpath_head *);
> +void scsi_mpath_put_head(struct scsi_mpath_head *);
> #else /* CONFIG_SCSI_MULTIPATH */
>
> +struct scsi_mpath_head {
> +};
> struct scsi_mpath_device {
> };
>
> @@ -51,5 +69,16 @@ static inline int scsi_multipath_init(void)
> static inline void scsi_multipath_exit(void)
> {
> }
> +static inline void scsi_mpath_remove_device(struct scsi_mpath_device
> + *scsi_mpath_dev)
> +{
> +}
> +static inline int scsi_mpath_get_head(struct scsi_mpath_head *)
> +{
> + return 0;
> +}
> +static inline void scsi_mpath_put_head(struct scsi_mpath_head *)
> +{
> +}
> #endif /* CONFIG_SCSI_MULTIPATH */
> #endif /* _SCSI_SCSI_MULTIPATH_H */
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare at suse.com +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich
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