[PATCH v8 24/27] scsi: sd: support multipath disk

[John Garry <john.g.garry@oracle.com>]

From: John Garry <john.garry@linux.dev>

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/scsi_mpath_disk0/
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/scsi_mpath_disk0/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.garry@linux.dev>
---
 drivers/scsi/sd.c | 426 +++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 406 insertions(+), 20 deletions(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 60e071d23ddd0..27230ecc2337e 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -115,12 +115,30 @@ static mempool_t *sd_large_page_pool;
 static atomic_t sd_large_page_pool_users = ATOMIC_INIT(0);
 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 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_head *mpath_head = &scsi_mpath_head->mpath_head;
+
+	mpath_put_disk(mpath_head);
+	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 = {
@@ -817,7 +835,8 @@ 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);
 
@@ -4019,6 +4038,90 @@ static int sd_format_disk_name(char *prefix, int index, char *buf, int buflen)
 	return 0;
 }
 
+#ifdef CONFIG_SCSI_MULTIPATH
+static int sd_mpath_revalidate_head(struct scsi_disk *sdkp)
+{
+	struct sd_mpath_disk *sd_mpath_disk = sdkp->sd_mpath_disk;
+	struct scsi_mpath_head *scsi_mpath_head = sd_mpath_disk->scsi_mpath_head;
+	struct mpath_head *mpath_head = &scsi_mpath_head->mpath_head;
+	struct gendisk *disk = mpath_head->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 and zoned 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));
+
+	mpath_revalidate_paths(mpath_head);
+
+	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_mpath_head *scsi_mpath_head)
+{
+	struct sd_mpath_disk *sd_mpath_disk;
+	int ret;
+
+	list_for_each_entry(sd_mpath_disk, &sd_mpath_disks_list, entry) {
+		ret = sd_mpath_get_disk(sd_mpath_disk);
+		if (ret)
+			continue;
+
+		if (sd_mpath_disk->scsi_mpath_head == scsi_mpath_head)
+			return sd_mpath_disk;
+
+		sd_mpath_put_disk(sd_mpath_disk);
+	}
+
+	return NULL;
+}
+
+static int 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;
+	int ret;
+
+	ret = mpath_add_device(mpath_device, sdkp->disk,
+		dev_to_node(sdp->host->dma_dev), &sdp->host->mpath_nr_active);
+	if (ret)
+		return ret;
+	mpath_device_set_live(mpath_device);
+	return 0;
+}
+
 static ssize_t sd_mpath_device_delayed_removal_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t count)
 {
@@ -4048,13 +4151,260 @@ static const struct attribute_group sd_mpath_disk_attr_group = {
 	.attrs		= sd_mpath_disk_attrs,
 };
 
-__maybe_unused
 static const struct attribute_group *sd_mpath_disk_attr_groups[] = {
 	&sd_mpath_disk_attr_group,
 	&mpath_attr_group,
 	NULL
 };
 
+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;
+	char disk_name[DISK_NAME_LEN - 2];
+	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.
+	 */
+	mutex_lock(&sd_mpath_disks_lock);
+	sd_mpath_disk = sd_mpath_find_disk(scsi_mpath_head);
+	if (sd_mpath_disk) {
+		error = sized_strscpy(disk_name, mpath_head->disk->disk_name,
+				sizeof(disk_name));
+		if (error < 0) {
+			/*
+			 * Should not happen as would fail for the same when
+			 * allocating the sd_mpath_disk
+			 */
+			sd_mpath_put_disk(sd_mpath_disk);
+			mutex_unlock(&sd_mpath_disks_lock);
+			return error;
+		}
+		sd_mpath_disk->disk_count++;
+		mutex_unlock(&sd_mpath_disks_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;
+
+	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;
+
+	error = mpath_alloc_head_disk(mpath_head, &lim,
+				dev_to_node(dma_dev));
+	if (error)
+		goto out_free_disk;
+	disk = mpath_head->disk;
+
+	error = ida_alloc(&sd_index_ida, GFP_KERNEL);
+	if (error < 0) {
+		sdev_printk(KERN_WARNING, sdp, "sd_mpath_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 = sized_strscpy(disk_name, mpath_head->disk->disk_name,
+				sizeof(disk_name));
+	if (error < 0)
+		goto out_free_index;
+
+	device_initialize(&sd_mpath_disk->dev);
+	sd_mpath_disk->dev.class = &sd_mpath_disk_class;
+
+	/* undone in sd_mpath_disk_release() */
+	scsi_mpath_get_head(scsi_mpath_head);
+
+	error = dev_set_name(&sd_mpath_disk->dev, "scsi_mpath_disk%d",
+				scsi_mpath_head->index);
+	if (error) {
+		put_device(&sd_mpath_disk->dev);
+		goto out_unlock;
+	}
+
+	error = device_add(&sd_mpath_disk->dev);
+	if (error) {
+		put_device(&sd_mpath_disk->dev);
+		goto out_unlock;
+	}
+
+	mpath_head->parent = &sd_mpath_disk->dev;
+	mpath_head->drv_module = THIS_MODULE;
+	mpath_head->disk_groups = sd_mpath_disk_attr_groups;
+
+	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",
+		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(mpath_head);
+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 scsi_mpath_head *scsi_mpath_head = sd_mpath_disk->scsi_mpath_head;
+	struct mpath_head *mpath_head = &scsi_mpath_head->mpath_head;
+	bool remove = false;
+
+	mpath_synchronize(mpath_head);
+
+	if (mpath_clear_current_path(mpath_device))
+		mpath_synchronize(mpath_head);
+
+	mpath_delete_device(mpath_device);
+
+	mutex_lock(&sd_mpath_disks_lock);
+	sd_mpath_disk->disk_count--;
+	if (!sd_mpath_disk->disk_count && mpath_can_remove_head(mpath_head)) {
+		list_del_init(&sd_mpath_disk->entry);
+		remove = true;
+	}
+	mutex_unlock(&sd_mpath_disks_lock);
+	mpath_remove_sysfs_link(mpath_device);
+	mpath_device->disk = NULL;
+
+	if (remove) {
+		device_del(&sd_mpath_disk->dev);
+		mpath_remove_disk(mpath_head);
+	}
+	sd_mpath_put_disk(sd_mpath_disk);
+}
+
+static void sd_mpath_remove_head(struct scsi_mpath_head *scsi_mpath_head)
+{
+	struct mpath_head *mpath_head = &scsi_mpath_head->mpath_head;
+	struct sd_mpath_disk *sd_mpath_disk;
+	struct device *dev = &scsi_mpath_head->dev;
+
+	mutex_lock(&sd_mpath_disks_lock);
+	sd_mpath_disk = sd_mpath_find_disk(scsi_mpath_head);
+	if (!sd_mpath_disk) {
+		dev_warn(dev, "could not find mpath disk\n");
+		mutex_unlock(&sd_mpath_disks_lock);
+		return;
+	}
+
+	if (sd_mpath_disk->disk_count) {
+		dev_dbg(dev, "non-zero multipath disk count in removal\n");
+		sd_mpath_put_disk(sd_mpath_disk);
+		mutex_unlock(&sd_mpath_disks_lock);
+		return;
+	}
+
+	list_del_init(&sd_mpath_disk->entry);
+	mutex_unlock(&sd_mpath_disks_lock);
+
+	device_del(&sd_mpath_disk->dev);
+	mpath_remove_disk(mpath_head);
+	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 scsi_mpath_head *scsi_mpath_head;
+	struct mpath_head *mpath_head;
+	bool remove = false;
+
+	if (!sd_mpath_disk)
+		return;
+
+	scsi_mpath_dev = sdp->scsi_mpath_dev;
+	mpath_device = &scsi_mpath_dev->mpath_device;
+	scsi_mpath_head = sd_mpath_disk->scsi_mpath_head;
+	mpath_head = &scsi_mpath_head->mpath_head;
+
+	mutex_lock(&sd_mpath_disks_lock);
+	sd_mpath_disk->disk_count--;
+	if (!sd_mpath_disk->disk_count) {
+		list_del_init(&sd_mpath_disk->entry);
+		remove = true;
+	}
+	mutex_unlock(&sd_mpath_disks_lock);
+	mpath_device->disk = NULL;
+
+	if (remove) {
+		device_del(&sd_mpath_disk->dev);
+		mpath_remove_disk(mpath_head);
+	}
+	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 int sd_mpath_add_disk(struct scsi_disk *sdkp)
+{
+	return 0;
+}
+#endif
+
 /**
  *	sd_probe - called during driver initialization and whenever a
  *	new scsi device is attached to the system. It is called once
@@ -4078,7 +4428,7 @@ static int sd_probe(struct scsi_device *sdp)
 	struct device *dev = &sdp->sdev_gendev;
 	struct scsi_disk *sdkp;
 	struct gendisk *gd;
-	int index;
+	int index = -1;
 	int error;
 
 	scsi_autopm_get_device(sdp);
@@ -4107,22 +4457,33 @@ static int sd_probe(struct scsi_device *sdp)
 					 &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);
@@ -4142,6 +4503,7 @@ static int sd_probe(struct scsi_device *sdp)
 
 	error = device_add(&sdkp->disk_dev);
 	if (error) {
+		sd_mpath_fail_probe(sdkp);
 		put_device(&sdkp->disk_dev);
 		put_disk(gd);
 		goto out;
@@ -4149,10 +4511,6 @@ static int sd_probe(struct scsi_device *sdp)
 
 	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;
 
@@ -4171,6 +4529,7 @@ static int sd_probe(struct scsi_device *sdp)
 	sd_revalidate_disk(gd);
 	if (sdp->sector_size > PAGE_SIZE) {
 		if (sd_large_pool_create()) {
+			sd_mpath_fail_probe(sdkp);
 			error = -ENOMEM;
 			device_unregister(&sdkp->disk_dev);
 			put_disk(gd);
@@ -4178,6 +4537,12 @@ static int sd_probe(struct scsi_device *sdp)
 		}
 	}
 
+	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;
@@ -4192,6 +4557,7 @@ static int sd_probe(struct scsi_device *sdp)
 
 	error = device_add_disk(dev, gd, NULL);
 	if (error) {
+		sd_mpath_fail_probe(sdkp);
 		device_unregister(&sdkp->disk_dev);
 		put_disk(gd);
 		if (sdp->sector_size > PAGE_SIZE)
@@ -4199,6 +4565,19 @@ static int sd_probe(struct scsi_device *sdp)
 		goto out;
 	}
 
+	if (sdp->scsi_mpath_dev) {
+		error = sd_mpath_add_disk(sdkp);
+		if (error) {
+			sd_mpath_fail_probe(sdkp);
+			device_del(&sdkp->disk_dev);
+			del_gendisk(sdkp->disk);
+
+			put_disk(sdkp->disk);
+			if (sdp->sector_size > PAGE_SIZE)
+				sd_large_pool_destroy();
+			goto out;
+		}
+	}
 	if (sdkp->security) {
 		sdkp->opal_dev = init_opal_dev(sdkp, &sd_sec_submit);
 		if (sdkp->opal_dev)
@@ -4212,7 +4591,8 @@ static int sd_probe(struct scsi_device *sdp)
 	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:
@@ -4340,6 +4720,9 @@ static void sd_remove(struct scsi_device *sdp)
 	struct device *dev = &sdp->sdev_gendev;
 	struct scsi_disk *sdkp = dev_get_drvdata(dev);
 
+	if (sdp->scsi_mpath_dev)
+		sd_mpath_remove(sdkp);
+
 	scsi_autopm_get_device(sdkp->device);
 
 	device_del(&sdkp->disk_dev);
@@ -4508,6 +4891,9 @@ static struct scsi_driver sd_template = {
 	.resume			= sd_resume,
 	.init_command		= sd_init_command,
 	.uninit_command		= sd_uninit_command,
+#ifdef CONFIG_SCSI_MULTIPATH
+	.mpath_remove_head	= sd_mpath_remove_head,
+#endif
 	.done			= sd_done,
 	.eh_action		= sd_eh_action,
 	.eh_reset		= sd_eh_reset,
-- 
2.43.7