linux-kernel - Re: [RFC][PATCH 0/3] vfs: Use an xarray instead of inserted bookmarks to scan mount list

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Message-ID: <20210315131723.GW2577561@casper.infradead.org>
Date:   Mon, 15 Mar 2021 13:17:23 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Miklos Szeredi <miklos@...redi.hu>
Cc:     David Howells <dhowells@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Ian Kent <raven@...maw.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 0/3] vfs: Use an xarray instead of inserted
 bookmarks to scan mount list

On Mon, Mar 15, 2021 at 02:14:35PM +0100, Miklos Szeredi wrote:
> On Mon, Mar 15, 2021 at 1:07 PM David Howells <dhowells@...hat.com> wrote:
> >
> >
> > Hi Al, Miklós,
> >
> > Can we consider replacing the "insert cursor" approach we're currently
> > using for proc files to scan the current namespace's mount list[1] with
> > something that uses an xarray of mounts indexed by mnt_id?
> >
> > This has some advantages:
> >
> >  (1) It's simpler.  We don't need to insert dummy mount objects as
> >      bookmarks into the mount list and code that's walking the list doesn't
> >      have to carefully step over them.
> >
> >  (2) We can use the file position to represent the mnt_id and can jump to
> >      it directly - ie. using seek() to jump to a mount object by its ID.
> 
> What happens if the mount at the current position is removed?

xa_find() will move to the next one.