linux-kernel - Re: [PATCH v3] fs/buffer: remove the min and max limit checks in __getblk

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Message-ID: <u7fadbfaq5wm7nqhn4yewbn43h3ahxuqm536ly473uch2v5qfl@hpgo2dfg77jp>
Date: Wed, 25 Jun 2025 12:16:49 +0200
From: Jan Kara <jack@...e.cz>
To: Pankaj Raghav <p.raghav@...sung.com>
Cc: Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>, 
	mcgrof@...nel.org, Christian Brauner <brauner@...nel.org>, kernel@...kajraghav.com, 
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, gost.dev@...sung.com, 
	Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v3] fs/buffer: remove the min and max limit checks in
 __getblk_slow()

On Wed 25-06-25 10:37:04, Pankaj Raghav wrote:
> All filesystems will already check the max and min value of their block
> size during their initialization. __getblk_slow() is a very low-level
> function to have these checks. Remove them and only check for logical
> block size alignment.
> 
> Suggested-by: Matthew Wilcox <willy@...radead.org>
> Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>

I know this is a bikeshedding but FWIW this is in the should never trigger
territory so I'd be inclined to just make it WARN_ON_ONCE() and completely
delete it once we refactor bh apis to make sure nobody can call bh
functions with anything else than sb->s_blocksize.

								Honza

> ---
> Changes since v2:
> - Removed the max and min checks in __getblk_slow().
> 
>  fs/buffer.c | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/buffer.c b/fs/buffer.c
> index a14d281c6a74..a1aa01ebc0ce 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -1122,13 +1122,9 @@ __getblk_slow(struct block_device *bdev, sector_t block,
>  {
>  	bool blocking = gfpflags_allow_blocking(gfp);
>  
> -	if (unlikely(size & (bdev_logical_block_size(bdev) - 1) ||
> -		     (size < 512 || size > PAGE_SIZE))) {
> -		printk(KERN_ERR "getblk(): invalid block size %d requested\n",
> -					size);
> -		printk(KERN_ERR "logical block size: %d\n",
> -					bdev_logical_block_size(bdev));
> -
> +	if (unlikely(size & (bdev_logical_block_size(bdev) - 1))) {
> +		printk(KERN_ERR "getblk(): block size %d not aligned to logical block size %d\n",
> +		       size, bdev_logical_block_size(bdev));
>  		dump_stack();
>  		return NULL;
>  	}
> 
> base-commit: 6ae58121126dcf8efcc2611f216a36a5e50b8ad9
> -- 
> 2.49.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR