On Tue 26-03-24 13:47:22, Christian Brauner wrote:
> Currently a device is only really released once the umount returns to
> userspace due to how file closing works. That ultimately could cause
> an old umount assumption to be violated that concurrent umount and mount
> don't fail. So an exclusively held device with a temporary holder should
> be yielded before the filesystem is gone. Add a helper that allows
> callers to do that. This also allows us to remove the two holder ops
> that Linus wasn't excited about.
>
> Fixes: f3a608827d1f ("bdev: open block device as files") # mainline only
> Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
...
> @@ -1012,6 +1005,29 @@ struct file *bdev_file_open_by_path(const char *path, blk_mode_t mode,
> }
> EXPORT_SYMBOL(bdev_file_open_by_path);
>
> +static inline void bd_yield_claim(struct file *bdev_file)
> +{
> + struct block_device *bdev = file_bdev(bdev_file);
> + struct bdev_inode *bd_inode = BDEV_I(bdev_file->f_mapping->host);
> + void *holder = bdev_file->private_data;
> +
> + lockdep_assert_held(&bdev->bd_disk->open_mutex);
> +
> + if (WARN_ON_ONCE(IS_ERR_OR_NULL(holder)))
> + return;
> +
> + if (holder != bd_inode) {
> + bdev_yield_write_access(bdev_file);
Hum, what if we teached bdev_yield_write_access() about special bd_inode
holder and kept bdev_yield_write_access() and bd_yield_claim() separate as
they were before this patch? IMHO it would make code a bit more
understandable. Otherwise the patch looks good.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
