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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <1842689.1596468469@warthog.procyon.org.uk> <1845353.1596469795@warthog.procyon.org.uk> <20200811135419.GA1263716@miu.piliscsaba.redhat.com> <135551.1597240486@warthog.procyon.org.uk> To: Miklos Szeredi Cc: dhowells@redhat.com, Linus Torvalds , linux-fsdevel , Al Viro , Karel Zak , Jeff Layton , Miklos Szeredi , Nicolas Dichtel , Christian Brauner , Lennart Poettering , Linux API , Ian Kent , LSM , Linux Kernel Mailing List Subject: Re: file metadata via fs API (was: [GIT PULL] Filesystem Information) MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <137928.1597242232.1@warthog.procyon.org.uk> Date: Wed, 12 Aug 2020 15:23:52 +0100 Message-ID: <137929.1597242232@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Miklos Szeredi wrote: > The point is that generic operations already exist and no need to add > new, specialized ones to access metadata. open and read already exist, yes, but the metadata isn't currently in convenient inodes and dentries that you can just walk through. So you're going to end up with a specialised filesystem instead, I suspect. Basically, it's the same as your do-everything-through-/proc/self/fds/ approach. And it's going to be heavier. I don't know if you're planning on creating a superblock each time you do an O_ALT open, but you will end up creating some inodes, dentries and a file - even before you get to the reading bit. David