[PATCH] block: Do not reread partition table on exclusively open device

[Jan Kara <jack@xxxxxxx>]

Since commit 10c70d95c0f2 ("block: remove the bd_openers checks in
blk_drop_partitions") we allow rereading of partition table although
there are users of the block device. This has an undesirable consequence
that e.g. if sda and sdb are assembled to a RAID1 device md0 with
partitions, BLKRRPART ioctl on sda will rescan partition table and
create sda1 device. This partition device under a raid device confuses
some programs (such as libstorage-ng used for initial partitioning for
distribution installation) leading to failures.

Fix the problem refusing to rescan partitions if there is another user
that has the block device exclusively open.

Link: https://lore.kernel.org/all/20221130135344.2ul4cyfstfs3znxg@quack3
Fixes: 10c70d95c0f2 ("block: remove the bd_openers checks in blk_drop_partitions")
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
 block/blk.h   |  2 +-
 block/genhd.c |  7 +++++--
 block/ioctl.c | 12 +++++++-----
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/block/blk.h b/block/blk.h
index a186ea20f39d..8b75a95b28d6 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -436,7 +436,7 @@ static inline struct kmem_cache *blk_get_queue_kmem_cache(bool srcu)
 }
 struct request_queue *blk_alloc_queue(int node_id, bool alloc_srcu);
 
-int disk_scan_partitions(struct gendisk *disk, fmode_t mode);
+int disk_scan_partitions(struct gendisk *disk, fmode_t mode, void *owner);
 
 int disk_alloc_events(struct gendisk *disk);
 void disk_add_events(struct gendisk *disk);
diff --git a/block/genhd.c b/block/genhd.c
index 0f9769db2de8..012529d36f5b 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -356,7 +356,7 @@ void disk_uevent(struct gendisk *disk, enum kobject_action action)
 }
 EXPORT_SYMBOL_GPL(disk_uevent);
 
-int disk_scan_partitions(struct gendisk *disk, fmode_t mode)
+int disk_scan_partitions(struct gendisk *disk, fmode_t mode, void *owner)
 {
 	struct block_device *bdev;
 
@@ -366,6 +366,9 @@ int disk_scan_partitions(struct gendisk *disk, fmode_t mode)
 		return -EINVAL;
 	if (disk->open_partitions)
 		return -EBUSY;
+	/* Someone else has bdev exclusively open? */
+	if (disk->part0->bd_holder != owner)
+		return -EBUSY;
 
 	set_bit(GD_NEED_PART_SCAN, &disk->state);
 	bdev = blkdev_get_by_dev(disk_devt(disk), mode, NULL);
@@ -500,7 +503,7 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
 
 		bdev_add(disk->part0, ddev->devt);
 		if (get_capacity(disk))
-			disk_scan_partitions(disk, FMODE_READ);
+			disk_scan_partitions(disk, FMODE_READ, NULL);
 
 		/*
 		 * Announce the disk and partitions after all partitions are
diff --git a/block/ioctl.c b/block/ioctl.c
index 60121e89052b..96617512982e 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -467,9 +467,10 @@ static int blkdev_bszset(struct block_device *bdev, fmode_t mode,
  * user space. Note the separate arg/argp parameters that are needed
  * to deal with the compat_ptr() conversion.
  */
-static int blkdev_common_ioctl(struct block_device *bdev, fmode_t mode,
-				unsigned cmd, unsigned long arg, void __user *argp)
+static int blkdev_common_ioctl(struct file *file, fmode_t mode, unsigned cmd,
+			       unsigned long arg, void __user *argp)
 {
+	struct block_device *bdev = I_BDEV(file->f_mapping->host);
 	unsigned int max_sectors;
 
 	switch (cmd) {
@@ -527,7 +528,8 @@ static int blkdev_common_ioctl(struct block_device *bdev, fmode_t mode,
 			return -EACCES;
 		if (bdev_is_partition(bdev))
 			return -EINVAL;
-		return disk_scan_partitions(bdev->bd_disk, mode & ~FMODE_EXCL);
+		return disk_scan_partitions(bdev->bd_disk, mode & ~FMODE_EXCL,
+					    file);
 	case BLKTRACESTART:
 	case BLKTRACESTOP:
 	case BLKTRACETEARDOWN:
@@ -605,7 +607,7 @@ long blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg)
 		break;
 	}
 
-	ret = blkdev_common_ioctl(bdev, mode, cmd, arg, argp);
+	ret = blkdev_common_ioctl(file, mode, cmd, arg, argp);
 	if (ret != -ENOIOCTLCMD)
 		return ret;
 
@@ -674,7 +676,7 @@ long compat_blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg)
 		break;
 	}
 
-	ret = blkdev_common_ioctl(bdev, mode, cmd, arg, argp);
+	ret = blkdev_common_ioctl(file, mode, cmd, arg, argp);
 	if (ret == -ENOIOCTLCMD && disk->fops->compat_ioctl)
 		ret = disk->fops->compat_ioctl(bdev, mode, cmd, arg);
 
-- 
2.35.3