block: introduce GENHD_FL_HIDDEN

With this flag a driver can create a gendisk that can be used for I/O
submission inside the kernel, but which is not registered as user
facing block device.  This will be useful for the NVMe multipath
implementation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/genhd.c b/block/genhd.c
index 1174d24e405eed36a23658221a6b72591fb42ce4..835e907e6e0158c89c42f8368bb396cc72e29162 100644 (file)
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -585,6 +585,11 @@ static void register_disk(struct device *parent, struct gendisk *disk)
         */
        pm_runtime_set_memalloc_noio(ddev, true);
 
+       if (disk->flags & GENHD_FL_HIDDEN) {
+               dev_set_uevent_suppress(ddev, 0);
+               return;
+       }
+
        disk->part0.holder_dir = kobject_create_and_add("holders", &ddev->kobj);
        disk->slave_dir = kobject_create_and_add("slaves", &ddev->kobj);
 
@@ -616,6 +621,11 @@ exit:
        while ((part = disk_part_iter_next(&piter)))
                kobject_uevent(&part_to_dev(part)->kobj, KOBJ_ADD);
        disk_part_iter_exit(&piter);
+
+       err = sysfs_create_link(&ddev->kobj,
+                               &disk->queue->backing_dev_info->dev->kobj,
+                               "bdi");
+       WARN_ON(err);
 }
 
 /**
@@ -630,7 +640,6 @@ exit:
  */
 void device_add_disk(struct device *parent, struct gendisk *disk)
 {
-       struct backing_dev_info *bdi;
        dev_t devt;
        int retval;
 
@@ -639,7 +648,8 @@ void device_add_disk(struct device *parent, struct gendisk *disk)
         * parameters make sense.
         */
        WARN_ON(disk->minors && !(disk->major || disk->first_minor));
-       WARN_ON(!disk->minors && !(disk->flags & GENHD_FL_EXT_DEVT));
+       WARN_ON(!disk->minors &&
+               !(disk->flags & (GENHD_FL_EXT_DEVT | GENHD_FL_HIDDEN)));
 
        disk->flags |= GENHD_FL_UP;
 
@@ -648,18 +658,26 @@ void device_add_disk(struct device *parent, struct gendisk *disk)
                WARN_ON(1);
                return;
        }
-       disk_to_dev(disk)->devt = devt;
        disk->major = MAJOR(devt);
        disk->first_minor = MINOR(devt);
 
        disk_alloc_events(disk);
 
-       /* Register BDI before referencing it from bdev */
-       bdi = disk->queue->backing_dev_info;
-       bdi_register_owner(bdi, disk_to_dev(disk));
-
-       blk_register_region(disk_devt(disk), disk->minors, NULL,
-                           exact_match, exact_lock, disk);
+       if (disk->flags & GENHD_FL_HIDDEN) {
+               /*
+                * Don't let hidden disks show up in /proc/partitions,
+                * and don't bother scanning for partitions either.
+                */
+               disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
+               disk->flags |= GENHD_FL_NO_PART_SCAN;
+       } else {
+               /* Register BDI before referencing it from bdev */
+               disk_to_dev(disk)->devt = devt;
+               bdi_register_owner(disk->queue->backing_dev_info,
+                               disk_to_dev(disk));
+               blk_register_region(disk_devt(disk), disk->minors, NULL,
+                                   exact_match, exact_lock, disk);
+       }
        register_disk(parent, disk);
        blk_register_queue(disk);
 
@@ -669,10 +687,6 @@ void device_add_disk(struct device *parent, struct gendisk *disk)
         */
        WARN_ON_ONCE(!blk_get_queue(disk->queue));
 
-       retval = sysfs_create_link(&disk_to_dev(disk)->kobj, &bdi->dev->kobj,
-                                  "bdi");
-       WARN_ON(retval);
-
        disk_add_events(disk);
        blk_integrity_add(disk);
 }
@@ -701,7 +715,8 @@ void del_gendisk(struct gendisk *disk)
        set_capacity(disk, 0);
        disk->flags &= ~GENHD_FL_UP;
 
-       sysfs_remove_link(&disk_to_dev(disk)->kobj, "bdi");
+       if (!(disk->flags & GENHD_FL_HIDDEN))
+               sysfs_remove_link(&disk_to_dev(disk)->kobj, "bdi");
        if (disk->queue) {
                /*
                 * Unregister bdi before releasing device numbers (as they can
@@ -712,13 +727,15 @@ void del_gendisk(struct gendisk *disk)
        } else {
                WARN_ON(1);
        }
-       blk_unregister_region(disk_devt(disk), disk->minors);
+
+       if (!(disk->flags & GENHD_FL_HIDDEN)) {
+               blk_unregister_region(disk_devt(disk), disk->minors);
+               kobject_put(disk->part0.holder_dir);
+               kobject_put(disk->slave_dir);
+       }
 
        part_stat_set_all(&disk->part0, 0);
        disk->part0.stamp = 0;
-
-       kobject_put(disk->part0.holder_dir);
-       kobject_put(disk->slave_dir);
        if (!sysfs_deprecated)
                sysfs_remove_link(block_depr, dev_name(disk_to_dev(disk)));
        pm_runtime_set_memalloc_noio(disk_to_dev(disk), false);
@@ -781,6 +798,10 @@ struct gendisk *get_gendisk(dev_t devt, int *partno)
                spin_unlock_bh(&ext_devt_lock);
        }
 
+       if (unlikely(disk->flags & GENHD_FL_HIDDEN)) {
+               put_disk(disk);
+               disk = NULL;
+       }
        return disk;
 }
 EXPORT_SYMBOL(get_gendisk);
@@ -1024,6 +1045,15 @@ static ssize_t disk_removable_show(struct device *dev,
                       (disk->flags & GENHD_FL_REMOVABLE ? 1 : 0));
 }
 
+static ssize_t disk_hidden_show(struct device *dev,
+                                  struct device_attribute *attr, char *buf)
+{
+       struct gendisk *disk = dev_to_disk(dev);
+
+       return sprintf(buf, "%d\n",
+                      (disk->flags & GENHD_FL_HIDDEN ? 1 : 0));
+}
+
 static ssize_t disk_ro_show(struct device *dev,
                                   struct device_attribute *attr, char *buf)
 {
@@ -1061,6 +1091,7 @@ static ssize_t disk_discard_alignment_show(struct device *dev,
 static DEVICE_ATTR(range, S_IRUGO, disk_range_show, NULL);
 static DEVICE_ATTR(ext_range, S_IRUGO, disk_ext_range_show, NULL);
 static DEVICE_ATTR(removable, S_IRUGO, disk_removable_show, NULL);
+static DEVICE_ATTR(hidden, S_IRUGO, disk_hidden_show, NULL);
 static DEVICE_ATTR(ro, S_IRUGO, disk_ro_show, NULL);
 static DEVICE_ATTR(size, S_IRUGO, part_size_show, NULL);
 static DEVICE_ATTR(alignment_offset, S_IRUGO, disk_alignment_offset_show, NULL);
@@ -1085,6 +1116,7 @@ static struct attribute *disk_attrs[] = {
        &dev_attr_range.attr,
        &dev_attr_ext_range.attr,
        &dev_attr_removable.attr,
+       &dev_attr_hidden.attr,
        &dev_attr_ro.attr,
        &dev_attr_size.attr,
        &dev_attr_alignment_offset.attr,

diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 5c0ed5db33c2d3e729eb3473a628787c4b9fcddf..93aae3476f58b7c124a908a777be3049a8de2234 100644 (file)
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -140,6 +140,7 @@ struct hd_struct {
 #define GENHD_FL_NATIVE_CAPACITY               128
 #define GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE    256
 #define GENHD_FL_NO_PART_SCAN                  512
+#define GENHD_FL_HIDDEN                                1024
 
 enum {
        DISK_EVENT_MEDIA_CHANGE                 = 1 << 0, /* media changed */