From mboxrd@z Thu Jan 1 00:00:00 1970 From: Karel Zak Date: Tue, 31 Mar 2020 08:34:30 +0000 Subject: Re: Upcoming: Notifications, FS notifications and fsinfo() Message-Id: <20200331083430.kserp35qabnxvths@ws.net.home> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit List-Id: References: <1445647.1585576702@warthog.procyon.org.uk> <20200330211700.g7evnuvvjenq3fzm@wittgenstein> In-Reply-To: To: Miklos Szeredi Cc: Christian Brauner , David Howells , Linus Torvalds , Al Viro , dray@redhat.com, Miklos Szeredi , Steven Whitehouse , Jeff Layton , Ian Kent , andres@anarazel.de, keyrings@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Lennart Poettering , Aleksa Sarai On Tue, Mar 31, 2020 at 07:11:11AM +0200, Miklos Szeredi wrote: > On Mon, Mar 30, 2020 at 11:17 PM Christian Brauner > wrote: > > > Fwiw, putting down my kernel hat and speaking as someone who maintains > > two container runtimes and various other low-level bits and pieces in > > userspace who'd make heavy use of this stuff I would prefer the fd-based > > fsinfo() approach especially in the light of across namespace > > operations, querying all properties of a mount atomically all-at-once, > > fsinfo(2) doesn't meet the atomically all-at-once requirement. I guess your /proc based idea have exactly the same problem... I see two possible ways: - after open("/mnt", O_PATH) create copy-on-write object in kernel to represent mount node -- kernel will able to modify it, but userspace will get unchanged data from the FD until to close() - improve fsinfo() to provide set (list) of the attributes by one call Karel -- Karel Zak http://karelzak.blogspot.com