linux-kernel - Re: [PATCH 09/11] vfs, fscache: Add an IS_KERNEL_FILE() macro for the S_KERNEL

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Message-ID: <YeefizLOGt1Qf35o@infradead.org>
Date:   Tue, 18 Jan 2022 21:20:11 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     David Howells <dhowells@...hat.com>
Cc:     Christoph Hellwig <hch@...radead.org>, linux-cachefs@...hat.com,
        Jeff Layton <jlayton@...nel.org>,
        Trond Myklebust <trondmy@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        Steve French <smfrench@...il.com>,
        Dominique Martinet <asmadeus@...ewreck.org>,
        Matthew Wilcox <willy@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Omar Sandoval <osandov@...ndov.com>,
        JeffleXu <jefflexu@...ux.alibaba.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-afs@...ts.infradead.org, linux-nfs@...r.kernel.org,
        linux-cifs@...r.kernel.org, ceph-devel@...r.kernel.org,
        v9fs-developer@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 09/11] vfs, fscache: Add an IS_KERNEL_FILE() macro for
 the S_KERNEL_FILE flag

On Tue, Jan 18, 2022 at 05:40:14PM +0000, David Howells wrote:
> Christoph Hellwig <hch@...radead.org> wrote:
> 
> > On Tue, Jan 18, 2022 at 01:54:54PM +0000, David Howells wrote:
> > > Add an IS_KERNEL_FILE() macro to test the S_KERNEL_FILE inode flag as is
> > > common practice for the other inode flags[1].
> > 
> > Please fix the flag to have a sensible name first, as the naming of the
> > flag and this new helper is utterly wrong as we already discussed.
> 
> And I suggested a new name, which you didn't comment on.

Again, look at the semantics of the flag:  The only thing it does in the
VFS is to prevent a rmdir.  So you might want to name it after that.

Or in fact drop the flag entirely.  We don't have that kind of
protection for other in-kernel file use or important userspace daemons
either.  I can't see why cachefiles is the magic snowflake here that
suddenly needs semantics no one else has.