Re: [PATCH 5/5] buffer: Fix various functions for block size > PAGE_SIZE

[Pankaj Raghav <p.raghav@samsung.com>]

On Tue, Nov 07, 2023 at 07:41:52PM +0000, Matthew Wilcox (Oracle) wrote:
> If i_blkbits is larger than PAGE_SHIFT, we shift by a negative number,
> which is undefined.  It is safe to shift the block left as a block
> device must be smaller than MAX_LFS_FILESIZE, which is guaranteed to
> fit in loff_t.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Looks good,
Reviewed-by: Pankaj Raghav <p.raghav@samsung.com>

> ---
>  fs/buffer.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/buffer.c b/fs/buffer.c
> index 2f08af3c47a2..5bdfcf8c6fe6 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -199,7 +199,7 @@ __find_get_block_slow(struct block_device *bdev, sector_t block)
>  	int all_mapped = 1;
>  	static DEFINE_RATELIMIT_STATE(last_warned, HZ, 1);
>  
> -	index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
> +	index = ((loff_t)block << bd_inode->i_blkbits) / PAGE_SIZE;