block: also call ->open for incremental partition opens

For whole devices ->open is called for each open, but for partitions it
is only called on the first open of a partition, e.g.:

  open("/dev/vdb", ...)
  open("/dev/vdb", ...)
    - 2 call to ->open

  open("/dev/vdb1", ...)
  open("/dev/vdb", ...)
    - 2 call to ->open

  open("/dev/vdb", ...)
  open("/dev/vdb", ...)
    - just open call to ->open

This is problematic as various block drivers look at open flags and
might not do all the required setup if the earlier open was with an
odd flag like O_NDELAY or the magic 3 ioctl-only open mode.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Phillip Potter <phil@philpotter.co.uk>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Acked-by: Christian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/r/20230608110258.189493-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 8 insertions, 10 deletions

diff --git a/block/bdev.c b/block/bdev.c
index 5c46ff107706..981f61357951 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -683,9 +683,6 @@ static int blkdev_get_part(struct block_device *part, fmode_t mode)
 	struct gendisk *disk = part->bd_disk;
 	int ret;
 
-	if (atomic_read(&part->bd_openers))
-		goto done;
-
 	ret = blkdev_get_whole(bdev_whole(part), mode);
 	if (ret)
 		return ret;
@@ -694,9 +691,10 @@ static int blkdev_get_part(struct block_device *part, fmode_t mode)
 	if (!bdev_nr_sectors(part))
 		goto out_blkdev_put;
 
-	disk->open_partitions++;
-	set_init_blocksize(part);
-done:
+	if (!atomic_read(&part->bd_openers)) {
+		disk->open_partitions++;
+		set_init_blocksize(part);
+	}
 	atomic_inc(&part->bd_openers);
 	return 0;
 
@@ -709,10 +707,10 @@ static void blkdev_put_part(struct block_device *part, fmode_t mode)
 {
 	struct block_device *whole = bdev_whole(part);
 
-	if (!atomic_dec_and_test(&part->bd_openers))
-		return;
-	blkdev_flush_mapping(part);
-	whole->bd_disk->open_partitions--;
+	if (atomic_dec_and_test(&part->bd_openers)) {
+		blkdev_flush_mapping(part);
+		whole->bd_disk->open_partitions--;
+	}
 	blkdev_put_whole(whole, mode);
 }