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

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Message-ID: <jbtntrppqjzaq6tdfzvwojjsnpacrdmg74vcvab4dc2z6hlhnl@ntotjsab5ice>
Date: Wed, 25 Jun 2025 12:53:54 +0200
From: "Pankaj Raghav (Samsung)" <kernel@...kajraghav.com>
To: Jan Kara <jack@...e.cz>
Cc: Pankaj Raghav <p.raghav@...sung.com>, 
	Alexander Viro <viro@...iv.linux.org.uk>, mcgrof@...nel.org, Christian Brauner <brauner@...nel.org>, 
	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, Jun 25, 2025 at 12:16:49PM +0200, Jan Kara wrote:
> 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.
> 
Something like this:

diff --git a/fs/buffer.c b/fs/buffer.c
index a1aa01ebc0ce..a49b4be37c62 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1122,10 +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))) {
+       if (WARN_ON_ONCE(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;
        }

I assume we don't need the dump_stack() anymore as we will print them
with WARN_ON_ONCE anyway?

--
Pankaj