Re: [PATCH v11 7/8] xfs: Implement ->notify_failure() for XFS

From: Christoph Hellwig <hch@infradead.org>
To: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Cc: Christoph Hellwig <hch@infradead.org>,
	linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org,
	nvdimm@lists.linux.dev, linux-mm@kvack.org,
	linux-fsdevel@vger.kernel.org, djwong@kernel.org,
	dan.j.williams@intel.com, david@fromorbit.com,
	jane.chu@oracle.com
Subject: Re: [PATCH v11 7/8] xfs: Implement ->notify_failure() for XFS
Date: Wed, 30 Mar 2022 08:52:21 -0700	[thread overview]
Message-ID: <YkR8tfSn+M51fbff@infradead.org> (raw)
In-Reply-To: <894ed00b-b174-6a10-ee45-320007957ea4@fujitsu.com>

On Wed, Mar 30, 2022 at 11:16:10PM +0800, Shiyang Ruan wrote:
> > > +#if IS_ENABLED(CONFIG_MEMORY_FAILURE) && IS_ENABLED(CONFIG_FS_DAX)
> > 
> > No real need for the IS_ENABLED.  Also any reason to even build this
> > file if the options are not set?  It seems like
> > xfs_dax_holder_operations should just be defined to NULL and the
> > whole file not supported if we can't support the functionality.
> 
> Got it.  These two CONFIG seem not related for now.  So, I think I should
> wrap these code with #ifdef CONFIG_MEMORY_FAILURE here, and add
> `xfs-$(CONFIG_FS_DAX) += xfs_notify_failure.o` in the makefile.

I'd do

ifeq ($(CONFIG_MEMORY_FAILURE),y)
xfs-$(CONFIG_FS_DAX) += xfs_notify_failure.o
endif

in the makefile and keep it out of the actual source file entirely.

> > > +
> > > +	/* Ignore the range out of filesystem area */
> > > +	if ((offset + len) < ddev_start)
> > 
> > No need for the inner braces.
> > 
> > > +	if ((offset + len) > ddev_end)
> > 
> > No need for the braces either.
> 
> Really no need?  It is to make sure the range to be handled won't out of the
> filesystem area.  And make sure the @offset and @len are valid and correct
> after subtract the bbdev_start.

Yes, but there is no need for the braces per the precedence rules in
C.  So these could be:

	if (offset + len < ddev_start)

and

	if (offset + len > ddev_end)