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Message-ID: <39bc040e9bb88b47f386baa09ed4a508281ce7d6.camel@redhat.com>
Subject: Re: [PATCH 02/67] vfs: Provide S_KERNEL_FILE inode flag
From:   Jeff Layton <jlayton@redhat.com>
To:     David Howells <dhowells@redhat.com>, linux-cachefs@redhat.com
Cc:     Trond Myklebust <trondmy@hammerspace.com>,
        Anna Schumaker <anna.schumaker@netapp.com>,
        Steve French <sfrench@samba.org>,
        Dominique Martinet <asmadeus@codewreck.org>,
        Matthew Wilcox <willy@infradead.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Omar Sandoval <osandov@osandov.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org,
        linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org,
        v9fs-developer@lists.sourceforge.net,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Date:   Tue, 19 Oct 2021 14:10:19 -0400
In-Reply-To: <163456865277.2614702.2064731306330022896.stgit@warthog.procyon.org.uk>
References: <163456861570.2614702.14754548462706508617.stgit@warthog.procyon.org.uk>
         <163456865277.2614702.2064731306330022896.stgit@warthog.procyon.org.uk>
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On Mon, 2021-10-18 at 15:50 +0100, David Howells wrote:
> Provide an S_KERNEL_FILE inode flag that a kernel service, e.g. cachefiles,
> can set to ward off other kernel services and drivers (including itself)
> from using files it is actively using.
> 
> Signed-off-by: David Howells <dhowells@redhat.com>
> ---
> 
>  include/linux/fs.h |    1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index e7a633353fd2..197493507744 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2250,6 +2250,7 @@ struct super_operations {
>  #define S_ENCRYPTED	(1 << 14) /* Encrypted file (using fs/crypto/) */
>  #define S_CASEFOLD	(1 << 15) /* Casefolded file */
>  #define S_VERITY	(1 << 16) /* Verity file (using fs/verity/) */
> +#define S_KERNEL_FILE	(1 << 17) /* File is in use by the kernel (eg. fs/cachefiles) */
>  
>  /*
>   * Note that nosuid etc flags are inode-specific: setting some file-system
> 
> 

It'd be better to fold this in with the patch where the first user is
added. That would make it easier to see how you intend to use it.
-- 
Jeff Layton <jlayton@redhat.com>