linux-ext4 - Re: fsync() errors is unsafe and risks data loss

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Message-ID: <20180419010819.GD23194@thunk.org>
Date:   Wed, 18 Apr 2018 21:08:19 -0400
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Dave Chinner <david@...morbit.com>,
        Jeff Layton <jlayton@...hat.com>,
        lsf-pc <lsf-pc@...ts.linuxfoundation.org>,
        Andres Freund <andres@...razel.de>,
        Andreas Dilger <adilger@...ger.ca>,
        Ext4 Developers List <linux-ext4@...r.kernel.org>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        "Joshua D. Drake" <jd@...mandprompt.com>
Subject: Re: fsync() errors is unsafe and risks data loss

On Wed, Apr 18, 2018 at 05:40:37PM -0700, Matthew Wilcox wrote:
> 
> I've been thinking about this.  Ideally we want to pass some kind of
> notification all the way up to the desktop and tell the user to plug the
> damn stick back in.  Then have the USB stick become the same blockdev
> that it used to be, and complete the writeback.  We are so far from
> being able to do that right now that it's not even funny.o

Maybe we shouldn't be trying to do any of this in the kernel, or at
least as little as possible in the kernel?  Perhaps it would be better
to do most of this as a device mapper hack; I suspect we'll need
userspace help to igure out whether the user has plugged the same USB
stick in, or a different USB stick, anyway.

					- Ted