[PATCH v2 02/18] scsi-multipath: introduce scsi_device head structure
John Garry
john.g.garry at oracle.com
Tue Apr 28 04:14:31 PDT 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.
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.
A new class for multipathed devices is added, scsi_mpath_device_class.
The purpose of this class is for managing the scsi_mpath_head.dev member.
The naming for the scsi_device structure is in form H:C:I:L,
where H is host, C is channel, I is ID, and L is lun.
However, for a multipathed scsi_device, all the naming members may be
different between member scsi_device's. As such, just use a simple
single-number naming index for each scsi_mpath_head.
The sysfs device folder will have links to the scsi_device's so, it will
be possible to lookup the member scsi_device's.
An example sysfs entry is as follows:
# ls -l /sys/class/scsi_mpath_device/scsi_mpath_device0/
total 0
drwxr-xr-x 2 root root 0 Apr 13 15:48 power
lrwxrwxrwx 1 root root 0 Apr 13 15:48 subsystem -> ../../../../class/scsi_mpath_device
-rw-r--r-- 1 root root 4096 Apr 13 15:48 uevent
-r--r--r-- 1 root root 4096 Apr 13 15:48 vpd_id
Signed-off-by: John Garry <john.g.garry at oracle.com>
---
drivers/scsi/scsi_multipath.c | 209 +++++++++++++++++++++++++++++++++-
drivers/scsi/scsi_sysfs.c | 3 +
include/scsi/scsi_multipath.h | 29 +++++
3 files changed, 239 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/scsi_multipath.c b/drivers/scsi/scsi_multipath.c
index ff37cfdf2f9d1..18d50d051b3ba 100644
--- a/drivers/scsi/scsi_multipath.c
+++ b/drivers/scsi/scsi_multipath.c
@@ -27,6 +27,10 @@ static const char *scsi_multipath_modes[] = {
static int scsi_multipath = SCSI_MULTIPATH_OFF;
+static LIST_HEAD(scsi_mpath_heads_list);
+static DEFINE_MUTEX(scsi_mpath_heads_lock);
+static DEFINE_IDA(scsi_multipath_dev_ida);
+
static int scsi_multipath_param_set(const char *val, const struct kernel_param *kp)
{
if (!val)
@@ -69,6 +73,60 @@ static int scsi_mpath_unique_lun_id(struct scsi_device *sdev)
return 0;
}
+static void scsi_mpath_head_release(struct device *dev)
+{
+ struct scsi_mpath_head *scsi_mpath_head =
+ container_of(dev, struct scsi_mpath_head, dev);
+ struct mpath_head *mpath_head = scsi_mpath_head->mpath_head;
+
+ ida_free(&scsi_multipath_dev_ida, scsi_mpath_head->index);
+ mpath_put_head(mpath_head);
+ kfree(scsi_mpath_head);
+}
+
+static ssize_t scsi_mpath_device_vpd_id_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct scsi_mpath_head *scsi_mpath_head =
+ container_of(dev, struct scsi_mpath_head, dev);
+
+ return sysfs_emit(buf, "%s\n", scsi_mpath_head->vpd_id);
+}
+static DEVICE_ATTR(vpd_id, S_IRUGO, scsi_mpath_device_vpd_id_show, NULL);
+
+static struct attribute *scsi_mpath_device_attrs[] = {
+ &dev_attr_vpd_id.attr,
+ NULL
+};
+
+static const struct attribute_group scsi_mpath_device_attrs_group = {
+ .attrs = scsi_mpath_device_attrs,
+};
+
+static bool scsi_multipath_sysfs_group_visible(struct kobject *kobj)
+{
+ return true;
+}
+
+static bool scsi_multipath_sysfs_attr_visible(struct kobject *kobj,
+ struct attribute *attr, int n)
+{
+ return false;
+}
+DEFINE_SYSFS_GROUP_VISIBLE(scsi_multipath_sysfs)
+
+const struct attribute_group *scsi_mpath_device_groups[] = {
+ &scsi_mpath_device_attrs_group,
+ NULL
+};
+
+static const struct class scsi_mpath_device_class = {
+ .name = "scsi_mpath_device",
+ .dev_groups = scsi_mpath_device_groups,
+ .dev_release = scsi_mpath_head_release,
+};
+
static int scsi_multipath_sdev_init(struct scsi_device *sdev)
{
struct Scsi_Host *shost = sdev->host;
@@ -88,6 +146,73 @@ static int scsi_multipath_sdev_init(struct scsi_device *sdev)
return 0;
}
+struct mpath_head_template smpdt = {
+};
+
+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);
+
+ 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;
+ 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;
+ kref_init(&scsi_mpath_head->ref);
+
+ device_initialize(&scsi_mpath_head->dev);
+ scsi_mpath_head->dev.class = &scsi_mpath_device_class;
+ ret = dev_set_name(&scsi_mpath_head->dev, "scsi_mpath_device%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;
+
+ 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->vpd_id,
+ scsi_mpath_dev->device_id_str,
+ SCSI_MPATH_DEVICE_ID_LEN) == 0) {
+
+ 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);
@@ -96,6 +221,7 @@ 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 == SCSI_MULTIPATH_OFF)
@@ -116,13 +242,58 @@ int scsi_mpath_dev_alloc(struct scsi_device *sdev)
goto out_uninit;
}
- return 0;
+ mutex_lock(&scsi_mpath_heads_lock);
+ scsi_mpath_head = scsi_mpath_find_head(sdev->scsi_mpath_dev);
+ if (scsi_mpath_head)
+ goto found;
+ scsi_mpath_head = scsi_mpath_alloc_head();
+ if (!scsi_mpath_head) {
+ sdev_printk(KERN_NOTICE, sdev, "could not allocate multipath head, device multipathing disabled\n");
+ mutex_unlock(&scsi_mpath_heads_lock);
+ goto out_uninit;
+ }
+ strscpy(scsi_mpath_head->vpd_id, sdev->scsi_mpath_dev->device_id_str,
+ SCSI_MPATH_DEVICE_ID_LEN);
+
+ ret = device_add(&scsi_mpath_head->dev);
+ if (ret) {
+ mutex_unlock(&scsi_mpath_heads_lock);
+ goto out_put_head;
+ }
+
+ list_add_tail(&scsi_mpath_head->entry, &scsi_mpath_heads_list);
+found:
+ mutex_unlock(&scsi_mpath_heads_lock);
+ ret = ida_alloc(&scsi_mpath_head->ida, GFP_KERNEL);
+ if (ret < 0)
+ goto out_put_head;
+ sdev->scsi_mpath_dev->index = ret;
+
+ sdev->scsi_mpath_dev->scsi_mpath_head = scsi_mpath_head;
+ return 0;
+out_put_head:
+ scsi_mpath_put_head(scsi_mpath_head);
out_uninit:
scsi_multipath_sdev_uninit(sdev);
return ret;
}
+static void scsi_mpath_remove_head(struct scsi_mpath_device *scsi_mpath_dev)
+{
+ scsi_mpath_put_head(scsi_mpath_dev->scsi_mpath_head);
+ scsi_mpath_dev->scsi_mpath_head = NULL;
+}
+
+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;
@@ -133,13 +304,47 @@ void scsi_mpath_dev_release(struct scsi_device *sdev)
scsi_multipath_sdev_uninit(sdev);
}
-int __init scsi_multipath_init(void)
+int scsi_mpath_get_head(struct scsi_mpath_head *scsi_mpath_head)
{
+ if (!kref_get_unless_zero(&scsi_mpath_head->ref))
+ return -ENXIO;
return 0;
}
+EXPORT_SYMBOL_GPL(scsi_mpath_get_head);
+
+static void scsi_mpath_free_head(struct kref *ref)
+{
+ struct scsi_mpath_head *scsi_mpath_head =
+ container_of(ref, struct scsi_mpath_head, ref);
+
+ /*
+ * If we race with scsi_mpath_find_head(), then that function may
+ * find this scsi_mpath_head in the heads list; however we would fail
+ * to take a reference to this scsi_mpath_head and continue the search.
+ * As such, it is safe to call device_unregister (and free
+ * scsi_mpath_head) after we delete this head from the list.
+ */
+ mutex_lock(&scsi_mpath_heads_lock);
+ list_del_init(&scsi_mpath_head->entry);
+ mutex_unlock(&scsi_mpath_heads_lock);
+
+ device_unregister(&scsi_mpath_head->dev);
+}
+
+void scsi_mpath_put_head(struct scsi_mpath_head *scsi_mpath_head)
+{
+ kref_put(&scsi_mpath_head->ref, scsi_mpath_free_head);
+}
+EXPORT_SYMBOL_GPL(scsi_mpath_put_head);
+
+int __init scsi_multipath_init(void)
+{
+ return class_register(&scsi_mpath_device_class);
+}
void __exit scsi_multipath_exit(void)
{
+ class_unregister(&scsi_mpath_device_class);
}
MODULE_LICENSE("GPL");
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 47534d9f2cf9b..043fd2d9cc417 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -1485,6 +1485,9 @@ 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 d3d410dafd17a..b3e0b98f39c56 100644
--- a/include/scsi/scsi_multipath.h
+++ b/include/scsi/scsi_multipath.h
@@ -19,12 +19,25 @@
#ifdef CONFIG_SCSI_MULTIPATH
#define SCSI_MPATH_DEVICE_ID_LEN 256
+struct scsi_mpath_head {
+ char vpd_id[SCSI_MPATH_DEVICE_ID_LEN];
+ struct list_head entry;
+ struct ida ida;
+ struct kref ref;
+ 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];
};
+
#define to_scsi_mpath_device(d) \
container_of(d, struct scsi_mpath_device, mpath_device)
@@ -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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