[PATCH 03/24] scsi-multipath: introduce scsi_device head structure
John Garry
john.g.garry at oracle.com
Wed Feb 25 07:36:06 PST 2026
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;
+ 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);
+ 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);
+
+ 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];
+ 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 */
--
2.43.5
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