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Mon, 3 Aug 2020 08:01:30 -0400 (EDT) Message-ID: <303106be4785135446e56cb606138a6e94885887.camel@themaw.net> Subject: Re: [PATCH 13/17] watch_queue: Implement mount topology and attribute change notifications [ver #5] From: Ian Kent To: David Howells , Miklos Szeredi Cc: Linus Torvalds , Al Viro , Casey Schaufler , Stephen Smalley , Nicolas Dichtel , Christian Brauner , andres@anarazel.de, Jeff Layton , dray@redhat.com, Karel Zak , keyrings@vger.kernel.org, Linux API , linux-fsdevel@vger.kernel.org, LSM , linux-kernel@vger.kernel.org Date: Mon, 03 Aug 2020 20:01:27 +0800 In-Reply-To: <1576646.1596455376@warthog.procyon.org.uk> References: <1293241.1595501326@warthog.procyon.org.uk> <158454378820.2863966.10496767254293183123.stgit@warthog.procyon.org.uk> <158454391302.2863966.1884682840541676280.stgit@warthog.procyon.org.uk> <2003787.1595585999@warthog.procyon.org.uk> <865566fb800a014868a9a7e36a00a14430efb11e.camel@themaw.net> <2023286.1595590563@warthog.procyon.org.uk> <1283475.1596449889@warthog.procyon.org.uk> <1576646.1596455376@warthog.procyon.org.uk> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.34.4 (3.34.4-1.fc31) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-api-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Mon, 2020-08-03 at 12:49 +0100, David Howells wrote: > Miklos Szeredi wrote: > > > OTOH mount notification is way smaller and IMO a more mature > > interface. So just picking the unique ID patch into this set might > > make sense. > > But userspace can't retrieve the unique ID without fsinfo() as things > stand. > > I'm changing it so that the fields are 64-bit, but initialised with > the > existing mount ID in the notifications set. The fsinfo set changes > that to a > unique ID. I'm tempted to make the unique IDs start at UINT_MAX+1 to > disambiguate them. Mmm ... so what would I use as a mount id that's not used, like NULL for strings? I'm using -1 now but changing this will mean I need something different. Could we set aside a mount id that will never be used so it can be used for this case? Maybe mount ids should start at 1 instead of zero ... Ian