linux-ext4 - Re: [PATCH v7 16/22] block: convert to errseq

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Date:   Tue, 27 Jun 2017 08:20:00 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Jeff Layton <jlayton@...hat.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        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,
        Chris Mason <clm@...com>, Josef Bacik <jbacik@...com>,
        David Sterba <dsterba@...e.com>,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        Carlos Maiolino <cmaiolino@...hat.com>,
        Eryu Guan <eguan@...hat.com>,
        David Howells <dhowells@...hat.com>,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-btrfs@...r.kernel.org, linux-block@...r.kernel.org
Subject: Re: [PATCH v7 16/22] block: convert to errseq_t based writeback
 error tracking

On Mon, Jun 26, 2017 at 10:34:18AM -0400, Jeff Layton wrote:
> The bigger question is -- what about more complex filesystems like
> ext4?  There are a couple of cases where we can return -EIO or -EROFS on
> fsync before filemap_write_and_wait_range is ever called. Like this one
> for instance:
> 
>         if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
>                 return -EIO;
> 
> ...and the EXT4_MF_FS_ABORTED case.
> 
> Are those conditions ever recoverable, such that a later fsync could
> succeed? IOW, could I do a remount or something such that the existing
> fds are left open and become usable again? 

This looks copied from the xfs forced shutdown code, and in that
case it's final and permanent - you'll need an unmount to
clear it.

> If so, then we really ought to advance the errseq_t in the file when we
> catch those cases as well. If we have to do that, then it probably makes
> sense to leave the ext4 patch as-is.

I think it can switch to the new file helper.