linux-kernel - Re: [PATCH v5 00/17] fs: introduce new writeback error reporting and convert ext2 and ext4 to use it

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Date:   Wed, 31 May 2017 14:37:13 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Jeff Layton <jlayton@...hat.com>
Cc:     Al Viro <viro@...IV.linux.org.uk>, Jan Kara <jack@...e.cz>,
        tytso@....edu, axboe@...nel.dk, mawilcox@...rosoft.com,
        ross.zwisler@...ux.intel.com, corbet@....net,
        linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v5 00/17] fs: introduce new writeback error reporting
 and convert ext2 and ext4 to use it

On Wed, 31 May 2017 17:31:49 -0400 Jeff Layton <jlayton@...hat.com> wrote:

> On Wed, 2017-05-31 at 13:27 -0700, Andrew Morton wrote:
> > On Wed, 31 May 2017 08:45:23 -0400 Jeff Layton <jlayton@...hat.com> wrote:
> > 
> > > This is v5 of the patchset to improve how we're tracking and reporting
> > > errors that occur during pagecache writeback.
> > 
> > I'm curious to know how you've been testing this?
> 
> >  Is that testing
> > strong enough for us to be confident that all nature of I/O errors
> > will be reported to userspace?
> > 
> 
> That's a tall order. This is a difficult thing to test as these sorts of
> errors are pretty rare by nature.
> 
> I have an xfstest that I posted just after this set that demonstrates
> that it works correctly, at least on ext2/3/4 when run by the ext4
> driver (ext2 legacy driver reports too many errors currently). I had
> btrfs and xfs working on that test too in an earlier incarnation of this
> set, so I think we can fix this in them as well without too much
> difficulty.
> 
> I'm happy to run other tests if someone wants to suggest them.
> 
> Now, all that said, I don't think this will make things any worse than
> they are today as far as reporting errors properly to userland goes.
> It's rather easy for an incidental synchronous writeback request from an
> internal caller to clear the AS_* flags today. This will at least ensure
> that we're reporting errors since a well-defined point in time when you
> call fsync.

Were you using error injection of some form?  If so, how was that all
set up?