block: Fix dev_t minor allocation lifetime

commit 2da78092dda13f1efd26edbbf99a567776913750 upstream.

Releases the dev_t minor when all references are closed to prevent
another device from acquiring the same major/minor.

Since the partition's release may be invoked from call_rcu's soft-irq
context, the ext_dev_idr's mutex had to be replaced with a spinlock so
as not so sleep.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
[bwh: Backported to 3.2:
 - Adjust filename
 - idr insertion API is different, and blk_alloc_devt() is preallocating
   a node in a different way]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/block/genhd.c b/block/genhd.c
index 8bd4ef2..3541581 100644 (file)
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -28,10 +28,10 @@ struct kobject *block_depr;
 /* for extended dynamic devt allocation, currently only one major is used */
 #define NR_EXT_DEVT            (1 << MINORBITS)
 
-/* For extended devt allocation.  ext_devt_mutex prevents look up
+/* For extended devt allocation.  ext_devt_lock prevents look up
  * results from going away underneath its user.
  */
-static DEFINE_MUTEX(ext_devt_mutex);
+static DEFINE_SPINLOCK(ext_devt_lock);
 static DEFINE_IDR(ext_devt_idr);
 
 static struct device_type disk_type;
@@ -421,13 +421,13 @@ int blk_alloc_devt(struct hd_struct *part, dev_t *devt)
        do {
                if (!idr_pre_get(&ext_devt_idr, GFP_KERNEL))
                        return -ENOMEM;
-               mutex_lock(&ext_devt_mutex);
+               spin_lock(&ext_devt_lock);
                rc = idr_get_new(&ext_devt_idr, part, &idx);
                if (!rc && idx >= NR_EXT_DEVT) {
                        idr_remove(&ext_devt_idr, idx);
                        rc = -EBUSY;
                }
-               mutex_unlock(&ext_devt_mutex);
+               spin_unlock(&ext_devt_lock);
        } while (rc == -EAGAIN);
 
        if (rc)
@@ -454,9 +454,9 @@ void blk_free_devt(dev_t devt)
                return;
 
        if (MAJOR(devt) == BLOCK_EXT_MAJOR) {
-               mutex_lock(&ext_devt_mutex);
+               spin_lock(&ext_devt_lock);
                idr_remove(&ext_devt_idr, blk_mangle_minor(MINOR(devt)));
-               mutex_unlock(&ext_devt_mutex);
+               spin_unlock(&ext_devt_lock);
        }
 }
 
@@ -663,7 +663,6 @@ void del_gendisk(struct gendisk *disk)
        if (!sysfs_deprecated)
                sysfs_remove_link(block_depr, dev_name(disk_to_dev(disk)));
        device_del(disk_to_dev(disk));
-       blk_free_devt(disk_to_dev(disk)->devt);
 }
 EXPORT_SYMBOL(del_gendisk);
 
@@ -688,13 +687,13 @@ struct gendisk *get_gendisk(dev_t devt, int *partno)
        } else {
                struct hd_struct *part;
 
-               mutex_lock(&ext_devt_mutex);
+               spin_lock(&ext_devt_lock);
                part = idr_find(&ext_devt_idr, blk_mangle_minor(MINOR(devt)));
                if (part && get_disk(part_to_disk(part))) {
                        *partno = part->partno;
                        disk = part_to_disk(part);
                }
-               mutex_unlock(&ext_devt_mutex);
+               spin_unlock(&ext_devt_lock);
        }
 
        return disk;
@@ -1102,6 +1101,7 @@ static void disk_release(struct device *dev)
 {
        struct gendisk *disk = dev_to_disk(dev);
 
+       blk_free_devt(dev->devt);
        disk_release_events(disk);
        kfree(disk->random);
        disk_replace_part_tbl(disk, NULL);

diff --git a/fs/partitions/check.c b/fs/partitions/check.c
index 1ef15cc..18c58e5 100644 (file)
--- a/fs/partitions/check.c
+++ b/fs/partitions/check.c
@@ -361,6 +361,7 @@ static const struct attribute_group *part_attr_groups[] = {
 static void part_release(struct device *dev)
 {
        struct hd_struct *p = dev_to_part(dev);
+       blk_free_devt(dev->devt);
        free_part_stats(p);
        free_part_info(p);
        kfree(p);
@@ -403,7 +404,6 @@ void delete_partition(struct gendisk *disk, int partno)
        rcu_assign_pointer(ptbl->last_lookup, NULL);
        kobject_put(part->holder_dir);
        device_del(part_to_dev(part));
-       blk_free_devt(part_devt(part));
 
        hd_struct_put(part);
 }