Re: [PATCH 55/78] block: change the hash used for looking up block devices

[Hannes Reinecke <hare@xxxxxxx>]

On 11/16/20 3:57 PM, 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@xxxxxx>
> ---
>   fs/block_dev.c | 26 ++------------------------
>   1 file changed, 2 insertions(+), 24 deletions(-)
>
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index d8664f5c1ff669..29db12c3bb501c 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;
> -}
> -
>   static 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;
>   
> @@ -910,6 +887,7 @@ static struct block_device *bdget(dev_t dev)
>                 bdev->bd_super = NULL;
>                 bdev->bd_inode = inode;
>                 bdev->bd_part_count = 0;
> +               bdev->bd_dev = dev;
>                 inode->i_mode = S_IFBLK;
>                 inode->i_rdev = dev;
>                 inode->i_bdev = bdev;
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>

Cheers,

Hannes
--
Dr. Hannes Reinecke                Kernel Storage Architect
hare@xxxxxxx                              +49 911 74053 688
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