linux-ext4 - Re: [PATCH 3/3] ext4: Gracefully handle ext4_break

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Message-ID: <20190524041829.GD2532@mit.edu>
Date:   Fri, 24 May 2019 00:18:29 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-ext4@...r.kernel.org, Ira Weiny <ira.weiny@...el.com>
Subject: Re: [PATCH 3/3] ext4: Gracefully handle ext4_break_layouts() failure
 during truncate

On Wed, May 22, 2019 at 11:03:17AM +0200, Jan Kara wrote:
> ext4_break_layouts() may fail e.g. due to a signal being delivered.
> Thus we need to handle its failure gracefully and not by taking the
> filesystem down. Currently ext4_break_layouts() failure is rare but it
> may become more common once RDMA uses layout leases for handling
> long-term page pins for DAX mappings.
> 
> To handle the failure we need to move ext4_break_layouts() earlier
> during setattr handling before we do hard to undo changes such as
> modifying inode sizhe. To be able to do that we also have to move some
> other checks which are better done uwithout holding i_mmap_sem earlier.
> 
> Reported-and-tested-by: Ira Weiny <ira.weiny@...el.com>
> Reviewed-by: Ira Weiny <ira.weiny@...el.com>
> Signed-off-by: Jan Kara <jack@...e.cz>hh

Thanks, applied.

What do people think about adding marking this for stable?  My take is
that DAX is still not that common for most stable kernel users, and
the patch moves enough stuff around that it's borderline for stable.
I'm going to leave off marking for stable unless someone wants to make
a case that we should so mark it.

       	       	     	       - Ted