linux-kernel - Re: [PATCH v11 7/8] xfs: Implement ->notify

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Date:   Wed, 30 Mar 2022 08:52:21 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Shiyang Ruan <ruansy.fnst@...itsu.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
        nvdimm@...ts.linux.dev, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, djwong@...nel.org,
        dan.j.williams@...el.com, david@...morbit.com, jane.chu@...cle.com
Subject: Re: [PATCH v11 7/8] xfs: Implement ->notify_failure() for XFS

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)