linux-kernel - Re: [PATCH v4] fs/buffer: remove the min and max limit checks in __getblk

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Message-ID: <20250629111506.7c58ccd7@pumpkin>
Date: Sun, 29 Jun 2025 11:15:06 +0100
From: David Laight <david.laight.linux@...il.com>
To: Baokun Li <libaokun1@...wei.com>
Cc: Pankaj Raghav <p.raghav@...sung.com>, Christian Brauner
 <brauner@...nel.org>, Jan Kara <jack@...e.cz>, <mcgrof@...nel.org>,
 Alexander Viro <viro@...iv.linux.org.uk>, <linux-kernel@...r.kernel.org>,
 <linux-fsdevel@...r.kernel.org>, <kernel@...kajraghav.com>,
 <gost.dev@...sung.com>, Matthew Wilcox <willy@...radead.org>, Zhang Yi
 <yi.zhang@...wei.com>, Yang Erkun <yangerkun@...wei.com>
Subject: Re: [PATCH v4] fs/buffer: remove the min and max limit checks in
 __getblk_slow()

On Fri, 27 Jun 2025 10:02:30 +0800
Baokun Li <libaokun1@...wei.com> wrote:

> On 2025/6/26 19:32, 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.
> >
> > As this check with logical block size alignment might never trigger, add
> > WARN_ON_ONCE() to the check. As WARN_ON_ONCE() will already print the
> > stack, remove the call to dump_stack().
> >
> > Suggested-by: Matthew Wilcox <willy@...radead.org>
> > Reviewed-by: Jan Kara <jack@...e.cz>
> > Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>  
> 
> Makes sense. Feel free to add:
> 
> Reviewed-by: Baokun Li <libaokun1@...wei.com>
> 
> > ---
> > Changes since v3:
> > - Use WARN_ON_ONCE on the logical block size check and remove the call
> >    to dump_stack.
> > - Use IS_ALIGNED() to check for aligned instead of open coding the
> >    check.
> >
> >   fs/buffer.c | 11 +++--------
> >   1 file changed, 3 insertions(+), 8 deletions(-)
> >
> > diff --git a/fs/buffer.c b/fs/buffer.c
> > index d61073143127..565fe88773c2 100644
> > --- a/fs/buffer.c
> > +++ b/fs/buffer.c
> > @@ -1122,14 +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));
> > -
> > -		dump_stack();
> > +	if (WARN_ON_ONCE(!IS_ALIGNED(size, bdev_logical_block_size(bdev)))) {
> > +		printk(KERN_ERR "getblk(): block size %d not aligned to logical block size %d\n",
> > +		       size, bdev_logical_block_size(bdev));
> >   		return NULL;

Shouldn't that use WARN_ONCE(condition, fmt, ...)

	David
 
> >   	}
> >   
> >
> > base-commit: b39f7d75dc41b5f5d028192cd5d66cff71179f35  
> 
> 
>