linux-kernel - Re: [PATCH 02/17] fs: remove the special !CONFIG_BLOCK def_blk

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Message-ID: <ZEbabjCZhl6j1Pk+@kbusch-mbp.dhcp.thefacebook.com>
Date:   Mon, 24 Apr 2023 13:37:18 -0600
From:   Keith Busch <kbusch@...nel.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        Miklos Szeredi <miklos@...redi.hu>,
        "Darrick J. Wong" <djwong@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Howells <dhowells@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        ceph-devel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, cluster-devel@...hat.com,
        linux-xfs@...r.kernel.org, linux-nfs@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/17] fs: remove the special !CONFIG_BLOCK def_blk_fops

On Mon, Apr 24, 2023 at 12:22:30PM -0700, Randy Dunlap wrote:
> On 4/23/23 22:49, Christoph Hellwig wrote:
> > +		if (IS_ENABLED(CONFIG_BLOCK))
> > +			inode->i_fop = &def_blk_fops;
> 
> It looks like def_blk_fops is being removed (commit message and patch
> fragment below), but here (above line) it is being used.
> 
> Am I just confused?

The def_blk_fops is removed only for the !CONFIG_BLOCK case. Its usage is under
a branch known at compile time, so it's optimized out for that case before
trying to resolve the symbol.