From mboxrd@z Thu Jan 1 00:00:00 1970 From: Karel Zak Date: Mon, 06 Apr 2020 09:17:01 +0000 Subject: Re: Upcoming: Notifications, FS notifications and fsinfo() Message-Id: <20200406091701.q7ctdek2grzryiu3@ws.net.home> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit List-Id: References: <2590640.1585757211@warthog.procyon.org.uk> <36e45eae8ad78f7b8889d9d03b8846e78d735d28.camel@themaw.net> <27994c53034c8f769ea063a54169317c3ee62c04.camel@themaw.net> <20200403111144.GB34663@gardel-login> <20200403151223.GB34800@gardel-login> <20200403203024.GB27105@fieldses.org> In-Reply-To: <20200403203024.GB27105@fieldses.org> To: "J. Bruce Fields" Cc: Lennart Poettering , Miklos Szeredi , Ian Kent , David Howells , Christian Brauner , Linus Torvalds , Al Viro , dray@redhat.com, Miklos Szeredi , Steven Whitehouse , Jeff Layton , andres@anarazel.de, keyrings@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Aleksa Sarai On Fri, Apr 03, 2020 at 04:30:24PM -0400, J. Bruce Fields wrote: > On Fri, Apr 03, 2020 at 05:12:23PM +0200, Lennart Poettering wrote: > > BTW, while we are at it: one more thing I'd love to see exposed by > > statx() is a simple flag whether the inode is a mount point. There's > > plenty code that implements a test like this all over the place, and > > it usually isn't very safe. There's one implementation in util-linux > > for example (in the /usr/bin/mountpoint binary), and another one in > > systemd. Would be awesome to just have a statx() return flag for that, > > that would make things *so* much easier and more robust. because in > > fact most code isn't very good that implements this, as much of it > > just compares st_dev of the specified file and its parent. Better code > > compares the mount ID, but as mentioned that's not as pretty as it > > could be so far... > > nfs-utils/support/misc/mountpoint.c:check_is_mountpoint() stats the file > and ".." and returns true if they have different st_dev or the same > st_ino. Comparing mount ids sounds better. BTW, this traditional st_dev+st_ino way is not reliable for bind mounts. For mountpoint(1) we search the directory in /proc/self/mountinfo. > So anyway, yes, everybody reinvents the wheel here, and this would be > useful. +1 Karel -- Karel Zak http://karelzak.blogspot.com