[PATCH 21/24] scsi: sd: support multipath disk
John Garry
john.g.garry at oracle.com
Wed Feb 25 07:36:24 PST 2026
Add support to attach a multipath disk.
We still allocate the gendisk per path, and this is required for the
per-path submission. However, those gendisks are marked as hidden. Those
disks are named sdX:Y, where X is the multipath disk index and Y is the
per-path index.
A global list of sd_mpath_disks is kept for matching scsi_device's.
The multipath gendisk has the name and disk->major/minor set to minic a
scsi_disk.
The following is an example of relevant scsi_disk and block sysfs
directories:
$ ls -l /sys/block/ | grep sdc
lrwxrwxrwx 1 root root 0 Feb 24 16:01 sdc -> ../devices/virtual/scsi_mpath_disk/0/sdc
lrwxrwxrwx 1 root root 0 Feb 24 16:01 sdc:0 -> ../devices/platform/host8/session1/target8:0:0/8:0:0:0/block/sdc:0
lrwxrwxrwx 1 root root 0 Feb 24 16:02 sdc:1 -> ../devices/platform/host9/session2/target9:0:0/9:0:0:0/block/sdc:1
$ ls -l /sys/class/scsi_mpath_disk/0/
total 0
drwxr-xr-x 2 root root 0 Feb 24 16:03 power
drwxr-xr-x 11 root root 0 Feb 24 16:01 sdc
lrwxrwxrwx 1 root root 0 Feb 24 16:01 subsystem -> ../../../../class/scsi_mpath_disk
-rw-r--r-- 1 root root 4096 Feb 24 16:01 uevent
$ ls -l /sys/class/scsi_mpath_disk/0/sdc/multipath/
total 0
lrwxrwxrwx 1 root root 0 Feb 24 16:20 sdc:0 -> ../../../../../platform/host8/session1/target8:0:0/8:0:0:0/block/sdc:0
lrwxrwxrwx 1 root root 0 Feb 24 16:20 sdc:1 -> ../../../../../platform/host9/session2/target9:0:0/9:0:0:0/block/sdc:1
$ ls -l /dev/sdc*
brw-rw---- 1 root disk 8, 32 Feb 24 16:01 /dev/sdc
brw-rw---- 1 root disk 8, 33 Feb 24 16:01 /dev/sdc1
brw-rw---- 1 root disk 8, 34 Feb 24 16:01 /dev/sdc2
$ lsblk /dev/sdc
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
sdc 8:32 0 600M 0 disk
|-sdc1 8:33 0 9M 0 part
`-sdc2 8:34 0 568M 0 part
Signed-off-by: John Garry <john.g.garry at oracle.com>
---
drivers/scsi/sd.c | 376 +++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 358 insertions(+), 18 deletions(-)
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 9617878b53ec6..409c0937764d9 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -117,12 +117,33 @@ static DEFINE_IDA(sd_index_ida);
static mempool_t *sd_page_pool;
static struct lock_class_key sd_bio_compl_lkclass;
#ifdef CONFIG_SCSI_MULTIPATH
+static LIST_HEAD(sd_mpath_disks_list);
+static DEFINE_MUTEX(sd_mpath_disks_lock);
+
struct sd_mpath_disk {
+ struct device dev;
+ int disk_index;
+ int disk_count;
+ struct list_head entry;
+ struct mutex lock;
struct mpath_disk *mpath_disk;
+ struct scsi_mpath_head *scsi_mpath_head;
};
static void sd_mpath_disk_release(struct device *dev)
{
+ struct sd_mpath_disk *sd_mpath_disk =
+ container_of(dev, struct sd_mpath_disk, dev);
+ struct scsi_mpath_head *scsi_mpath_head =
+ sd_mpath_disk->scsi_mpath_head;
+ struct mpath_disk *mpath_disk = sd_mpath_disk->mpath_disk;
+
+ mpath_put_disk(mpath_disk);
+
+ ida_free(&sd_index_ida, sd_mpath_disk->disk_index);
+ scsi_mpath_put_head(scsi_mpath_head);
+
+ kfree(sd_mpath_disk);
}
static const struct class sd_mpath_disk_class = {
@@ -4144,7 +4165,302 @@ static const struct scsi_mpath_pr_ops sd_mpath_pr_ops = {
.pr_read_keys = sd_mpath_pr_read_keys,
.pr_read_reservation = sd_mpath_pr_read_reservation,
};
+
+static int sd_mpath_revalidate_head(struct scsi_disk *sdkp)
+{
+ struct sd_mpath_disk *sd_mpath_disk = sdkp->sd_mpath_disk;
+ struct mpath_disk *mpath_disk = sd_mpath_disk->mpath_disk;;
+ struct gendisk *disk = mpath_disk->disk;
+ struct queue_limits *sdkp_lim = &sdkp->disk->queue->limits;
+ struct queue_limits lim;
+ unsigned int memflags;
+ int ret;
+
+ lim = queue_limits_start_update(disk->queue);
+ memflags = blk_mq_freeze_queue(disk->queue);
+
+ lim.logical_block_size = sdkp_lim->logical_block_size;
+ lim.physical_block_size = sdkp_lim->physical_block_size;
+ lim.io_min = sdkp_lim->io_min;
+ lim.io_opt = sdkp_lim->io_opt;
+
+ queue_limits_stack_bdev(&lim, sdkp->disk->part0, 0,
+ disk->disk_name);
+
+ /* TODO: setup integrity limits */
+ lim.max_write_streams = sdkp_lim->max_write_streams;
+ lim.write_stream_granularity = sdkp_lim->write_stream_granularity;
+ ret = queue_limits_commit_update(disk->queue, &lim);
+
+ set_capacity_and_notify(disk, get_capacity(sdkp->disk));
+
+ blk_mq_unfreeze_queue(disk->queue, memflags);
+
+ return ret;
+}
+static int sd_mpath_get_disk(struct sd_mpath_disk *sd_mpath_disk)
+{
+ if (!get_device(&sd_mpath_disk->dev))
+ return -ENXIO;
+ return 0;
+}
+
+static void sd_mpath_put_disk(struct sd_mpath_disk *sd_mpath_disk)
+{
+ put_device(&sd_mpath_disk->dev);
+}
+
+static struct sd_mpath_disk *sd_mpath_find_disk(struct scsi_device *sdp)
+{
+ struct scsi_mpath_device *scsi_mpath_dev = sdp->scsi_mpath_dev;
+ struct sd_mpath_disk *sd_mpath_disk;
+ int ret;
+
+ mutex_lock(&sd_mpath_disks_lock);
+ list_for_each_entry(sd_mpath_disk, &sd_mpath_disks_list, entry) {
+ struct scsi_mpath_head *scsi_mpath_head;
+ struct mpath_disk *mpath_disk;
+ struct mpath_head *mpath_head;
+
+ ret = sd_mpath_get_disk(sd_mpath_disk);
+ if (ret)
+ continue;
+ mpath_disk = sd_mpath_disk->mpath_disk;
+ mpath_head = mpath_disk->mpath_head;
+ scsi_mpath_head = mpath_head->drvdata;
+
+ if (strncmp(scsi_mpath_head->wwid,
+ scsi_mpath_dev->device_id_str,
+ SCSI_MPATH_DEVICE_ID_LEN) == 0) {
+
+ mutex_unlock(&sd_mpath_disks_lock);
+ return sd_mpath_disk;
+ }
+ sd_mpath_put_disk(sd_mpath_disk);
+ }
+
+ return NULL;
+}
+
+static void sd_mpath_add_disk(struct scsi_disk *sdkp)
+{
+ struct scsi_device *sdp = sdkp->device;
+ struct scsi_mpath_device *scsi_mpath_dev = sdp->scsi_mpath_dev;
+ struct mpath_device *mpath_device = &scsi_mpath_dev->mpath_device;
+ struct sd_mpath_disk *sd_mpath_disk = sdkp->sd_mpath_disk;
+ struct mpath_disk *mpath_disk = sd_mpath_disk->mpath_disk;
+ struct mpath_head *mpath_head = mpath_disk->mpath_head;
+
+ mpath_device->disk = sdkp->disk;
+ mpath_add_device(mpath_head, mpath_device);
+ mpath_device_set_live(mpath_disk, mpath_device);
+}
+
+static int sd_mpath_probe(struct scsi_disk *sdkp)
+{
+ struct scsi_device *sdp = sdkp->device;
+ struct scsi_mpath_device *scsi_mpath_dev = sdp->scsi_mpath_dev;
+ struct device *dma_dev = sdp->host->dma_dev;
+ struct scsi_mpath_head *scsi_mpath_head =
+ scsi_mpath_dev->scsi_mpath_head;
+ struct sd_mpath_disk *sd_mpath_disk;
+ struct mpath_head *mpath_head = scsi_mpath_head->mpath_head;
+ struct queue_limits lim;
+ struct gendisk *disk;
+ int error;
+
+ /*
+ * sd_mpath_disks_list is kept locked if no disk found.
+ * Otherwise an extra reference is taken.
+ */
+ sd_mpath_disk = sd_mpath_find_disk(sdp);
+ if (sd_mpath_disk) {
+ mutex_lock(&sd_mpath_disk->lock);
+ sd_mpath_disk->disk_count++;
+ mutex_unlock(&sd_mpath_disk->lock);
+ goto found;
+ }
+
+ sd_mpath_disk = kzalloc(sizeof(*sd_mpath_disk), GFP_KERNEL);
+ if (!sd_mpath_disk) {
+ error = -ENOMEM;
+ goto out_unlock;
+ }
+
+ sd_mpath_disk->scsi_mpath_head = scsi_mpath_head;
+ device_initialize(&sd_mpath_disk->dev);
+ mutex_init(&sd_mpath_disk->lock);
+ sd_mpath_disk->dev.class = &sd_mpath_disk_class;
+
+ blk_set_stacking_limits(&lim);
+ lim.dma_alignment = 3;
+ lim.features |= BLK_FEAT_IO_STAT | BLK_FEAT_NOWAIT |
+ BLK_FEAT_POLL | BLK_FEAT_ATOMIC_WRITES;
+
+ sd_mpath_disk->mpath_disk = mpath_alloc_head_disk(&lim,
+ dev_to_node(dma_dev));
+ if (!sd_mpath_disk->mpath_disk) {
+ error = -ENOMEM;
+ goto out_free_disk;
+ }
+ disk = sd_mpath_disk->mpath_disk->disk;
+ mpath_get_head(mpath_head); /* undone in mpath_free_disk() */
+
+ sd_mpath_disk->mpath_disk->mpath_head = mpath_head;
+ sd_mpath_disk->mpath_disk->parent = &sd_mpath_disk->dev;
+
+ error = ida_alloc(&sd_index_ida, GFP_KERNEL);
+ if (error < 0) {
+ sdev_printk(KERN_WARNING, sdp, "sd_probe: memory exhausted.\n");
+ goto out_put_disk;
+ }
+ sd_mpath_disk->disk_index = error;
+ error = sd_format_disk_name("sd", sd_mpath_disk->disk_index,
+ disk->disk_name, DISK_NAME_LEN);
+ if (error)
+ goto out_free_index;
+
+ error = dev_set_name(&sd_mpath_disk->dev, "%s",
+ dev_name(&scsi_mpath_head->dev));
+ if (error)
+ goto out_free_index;
+
+ /* undone in sd_mpath_disk_release() */
+ scsi_mpath_get_head(scsi_mpath_head);
+
+ error = device_add(&sd_mpath_disk->dev);
+ if (error) {
+ put_device(&sd_mpath_disk->dev);
+ goto out_unlock;
+ }
+
+ list_add_tail(&sd_mpath_disk->entry, &sd_mpath_disks_list);
+ disk->major = sd_major((sd_mpath_disk->disk_index & 0xf0) >> 4);
+ disk->first_minor = ((sd_mpath_disk->disk_index & 0xf) << 4) |
+ (sd_mpath_disk->disk_index & 0xfff00);
+ disk->minors = SD_MINORS;
+
+ sd_mpath_disk->disk_count = 1;
+ mutex_unlock(&sd_mpath_disks_lock);
+
+found:
+ sdkp->sd_mpath_disk = sd_mpath_disk;
+ sdkp->disk->flags |= GENHD_FL_HIDDEN;
+ snprintf(sdkp->disk->disk_name, DISK_NAME_LEN, "%s:%d",
+ sd_mpath_disk->mpath_disk->disk->disk_name,
+ scsi_mpath_dev->index);
+
+ sdkp->index = -1;
+ return 0;
+
+out_free_index:
+ ida_free(&sd_index_ida, sd_mpath_disk->disk_index);
+out_put_disk:
+ mpath_put_disk(sd_mpath_disk->mpath_disk);
+out_free_disk:
+ kfree(sd_mpath_disk);
+out_unlock:
+ mutex_unlock(&sd_mpath_disks_lock);
+ return error;
+}
+
+static void sd_mpath_remove(struct scsi_disk *sdkp)
+{
+ struct sd_mpath_disk *sd_mpath_disk = sdkp->sd_mpath_disk;
+ struct scsi_device *sdp = sdkp->device;
+ struct scsi_mpath_device *scsi_mpath_dev = sdp->scsi_mpath_dev;
+ struct mpath_device *mpath_device = &scsi_mpath_dev->mpath_device;
+ struct mpath_disk *mpath_disk = sd_mpath_disk->mpath_disk;
+ struct mpath_head *mpath_head = mpath_disk->mpath_head;
+ bool remove = false;
+
+ mpath_synchronize(mpath_head);
+
+ if (mpath_clear_current_path(mpath_head, mpath_device))
+ mpath_synchronize(mpath_head);
+
+ mpath_delete_device(mpath_head, mpath_device);
+
+ mutex_lock(&sd_mpath_disk->lock);
+ sd_mpath_disk->disk_count--;
+ /* delayed removal not yet supported */
+ if (!sd_mpath_disk->disk_count) {
+ mutex_lock(&sd_mpath_disks_lock);
+ list_del_init(&sd_mpath_disk->entry);
+ mutex_unlock(&sd_mpath_disks_lock);
+
+ remove = true;
+ }
+ mutex_unlock(&sd_mpath_disk->lock);
+ mpath_remove_sysfs_link(mpath_disk, mpath_device);
+ mpath_device->disk = NULL;
+
+ if (remove) {
+ device_del(&sd_mpath_disk->dev);
+ mpath_remove_disk(mpath_disk);
+ }
+ sd_mpath_put_disk(sd_mpath_disk);
+}
+
+/*
+ * Always calls for a failed probe, so we need to handle that some structures
+ * have not been setup.
+ */
+static void sd_mpath_fail_probe(struct scsi_disk *sdkp)
+{
+ struct sd_mpath_disk *sd_mpath_disk = sdkp->sd_mpath_disk;
+ struct scsi_mpath_device *scsi_mpath_dev;
+ struct mpath_device *mpath_device;
+ struct scsi_device *sdp = sdkp->device;
+ struct mpath_disk *mpath_disk;
+ bool remove = false;
+
+ if (!sd_mpath_disk)
+ return;
+
+ mpath_disk = sd_mpath_disk->mpath_disk;
+ scsi_mpath_dev = sdp->scsi_mpath_dev;
+ mpath_device = &scsi_mpath_dev->mpath_device;
+
+ mutex_lock(&sd_mpath_disk->lock);
+ sd_mpath_disk->disk_count--;
+ if (!sd_mpath_disk->disk_count) {
+ mutex_lock(&sd_mpath_disks_lock);
+ list_del_init(&sd_mpath_disk->entry);
+ mutex_unlock(&sd_mpath_disks_lock);
+
+ remove = true;
+ }
+ mutex_unlock(&sd_mpath_disk->lock);
+ mpath_device->disk = NULL;
+
+ if (remove) {
+ device_del(&sd_mpath_disk->dev);
+ mpath_remove_disk(mpath_disk);
+ }
+ sd_mpath_put_disk(sd_mpath_disk);
+}
+
#else /* CONFIG_SCSI_MULTIPATH */
+static int sd_mpath_probe(struct scsi_disk *sdkp)
+{
+ return 0;
+}
+static void sd_mpath_remove(struct scsi_disk *sdkp)
+{
+ return;
+}
+static void sd_mpath_fail_probe(struct scsi_disk *sdkp)
+{
+
+}
+static int sd_mpath_revalidate_head(struct scsi_disk *sdkp)
+{
+ return 0;
+}
+static void sd_mpath_add_disk(struct scsi_disk *sdkp)
+{
+}
#endif
/**
* sd_probe - called during driver initialization and whenever a
@@ -4198,22 +4514,33 @@ static int sd_probe(struct device *dev)
&sd_bio_compl_lkclass);
if (!gd)
goto out_free;
+ sdkp->disk = gd;
+ sdkp->device = sdp;
- index = ida_alloc(&sd_index_ida, GFP_KERNEL);
- if (index < 0) {
- sdev_printk(KERN_WARNING, sdp, "sd_probe: memory exhausted.\n");
- goto out_put;
- }
+ if (sdp->scsi_mpath_dev) {
+ error = sd_mpath_probe(sdkp);
+ if (error)
+ goto out_put;
+ } else {
+ index = ida_alloc(&sd_index_ida, GFP_KERNEL);
+ if (index < 0) {
+ sdev_printk(KERN_WARNING, sdp, "sd_probe: memory exhausted.\n");
+ goto out_put;
+ }
- error = sd_format_disk_name("sd", index, gd->disk_name, DISK_NAME_LEN);
- if (error) {
- sdev_printk(KERN_WARNING, sdp, "SCSI disk (sd) name length exceeded.\n");
- goto out_free_index;
+ error = sd_format_disk_name("sd", index, gd->disk_name,
+ DISK_NAME_LEN);
+ if (error) {
+ sdev_printk(KERN_WARNING, sdp, "SCSI disk (sd) name length exceeded.\n");
+ goto out_free_index;
+ }
+ sdkp->index = index;
+
+ gd->major = sd_major((index & 0xf0) >> 4);
+ gd->first_minor = ((index & 0xf) << 4) | (index & 0xfff00);
+ gd->minors = SD_MINORS;
}
- sdkp->device = sdp;
- sdkp->disk = gd;
- sdkp->index = index;
sdkp->max_retries = SD_MAX_RETRIES;
atomic_set(&sdkp->openers, 0);
atomic_set(&sdkp->device->ioerr_cnt, 0);
@@ -4233,16 +4560,13 @@ static int sd_probe(struct device *dev)
error = device_add(&sdkp->disk_dev);
if (error) {
+ sd_mpath_fail_probe(sdkp);
put_device(&sdkp->disk_dev);
goto out;
}
dev_set_drvdata(dev, sdkp);
- gd->major = sd_major((index & 0xf0) >> 4);
- gd->first_minor = ((index & 0xf) << 4) | (index & 0xfff00);
- gd->minors = SD_MINORS;
-
gd->fops = &sd_fops;
gd->private_data = sdkp;
@@ -4260,6 +4584,12 @@ static int sd_probe(struct device *dev)
sd_revalidate_disk(gd);
+ if (sdp->scsi_mpath_dev) {
+ error = sd_mpath_revalidate_head(sdkp);
+ if (error)
+ sdev_printk(KERN_WARNING, sdp, "could not revalidate multipath limits\n");
+ }
+
if (sdp->removable) {
gd->flags |= GENHD_FL_REMOVABLE;
gd->events |= DISK_EVENT_MEDIA_CHANGE;
@@ -4274,11 +4604,15 @@ static int sd_probe(struct device *dev)
error = device_add_disk(dev, gd, NULL);
if (error) {
+ sd_mpath_fail_probe(sdkp);
device_unregister(&sdkp->disk_dev);
put_disk(gd);
goto out;
}
+ if (sdp->scsi_mpath_dev)
+ sd_mpath_add_disk(sdkp);
+
if (sdkp->security) {
sdkp->opal_dev = init_opal_dev(sdkp, &sd_sec_submit);
if (sdkp->opal_dev)
@@ -4292,7 +4626,8 @@ static int sd_probe(struct device *dev)
return 0;
out_free_index:
- ida_free(&sd_index_ida, index);
+ if (index >= 0)
+ ida_free(&sd_index_ida, index);
out_put:
put_disk(gd);
out_free:
@@ -4316,6 +4651,10 @@ static int sd_probe(struct device *dev)
static int sd_remove(struct device *dev)
{
struct scsi_disk *sdkp = dev_get_drvdata(dev);
+ struct scsi_device *sdp = sdkp->device; // new code
+
+ if (sdp->scsi_mpath_dev)
+ sd_mpath_remove(sdkp);
scsi_autopm_get_device(sdkp->device);
@@ -4332,7 +4671,8 @@ static void scsi_disk_release(struct device *dev)
{
struct scsi_disk *sdkp = to_scsi_disk(dev);
- ida_free(&sd_index_ida, sdkp->index);
+ if (sdkp->index >= 0)
+ ida_free(&sd_index_ida, sdkp->index);
put_device(&sdkp->device->sdev_gendev);
free_opal_dev(sdkp->opal_dev);
--
2.43.5
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