Re: [PATCH] block: change the hash used for looking up block devices

[Eric Biggers <ebiggers@kernel.org>]

On Sun, Sep 27, 2020 at 09:11:15AM +0200, Christoph Hellwig wrote:
> Adding the minor to the major creates tons of pointless conflicts. Just
> use the dev_t itself, which is 32-bits and thus is guaranteed to fit
> into ino_t.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/block_dev.c | 25 +------------------------
>  1 file changed, 1 insertion(+), 24 deletions(-)
> 
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 6b9d19ffa5af7b..da7d4868057632 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -870,35 +870,12 @@ void __init bdev_cache_init(void)
>  	blockdev_superblock = bd_mnt->mnt_sb;   /* For writeback */
>  }
>  
> -/*
> - * Most likely _very_ bad one - but then it's hardly critical for small
> - * /dev and can be fixed when somebody will need really large one.
> - * Keep in mind that it will be fed through icache hash function too.
> - */
> -static inline unsigned long hash(dev_t dev)
> -{
> -	return MAJOR(dev)+MINOR(dev);
> -}
> -
> -static int bdev_test(struct inode *inode, void *data)
> -{
> -	return BDEV_I(inode)->bdev.bd_dev == *(dev_t *)data;
> -}
> -
> -static int bdev_set(struct inode *inode, void *data)
> -{
> -	BDEV_I(inode)->bdev.bd_dev = *(dev_t *)data;
> -	return 0;
> -}
> -
>  struct block_device *bdget(dev_t dev)
>  {
>  	struct block_device *bdev;
>  	struct inode *inode;
>  
> -	inode = iget5_locked(blockdev_superblock, hash(dev),
> -			bdev_test, bdev_set, &dev);
> -
> +	inode = iget_locked(blockdev_superblock, dev);
>  	if (!inode)
>  		return NULL;

Doesn't ->bd_dev still need to be set somewhere?

- Eric