linux-ext4 - Re: [PATCH v2 1/2] ext4: Close race between direct IO and ext4_break

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Date:   Tue, 11 Sep 2018 17:26:41 +0200
From:   Jan Kara <jack@...e.cz>
To:     sandeen@...hat.com
Cc:     Dave Jiang <dave.jiang@...el.com>, tytso@....edu,
        darrick.wong@...cle.com, jack@...e.cz, zwisler@...nel.org,
        linux-nvdimm@...ts.01.org, david@...morbit.com,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        lczerner@...hat.com, linux-ext4@...r.kernel.org, hch@....de
Subject: Re: [PATCH v2 1/2] ext4: Close race between direct IO and
 ext4_break_layouts()

On Mon 10-09-18 11:23:56, Eric Sandeen wrote:
> On 8/8/18 12:25 PM, Dave Jiang wrote:
> > From: Ross Zwisler <zwisler@...nel.org>
> > 
> > If the refcount of a page is lowered between the time that it is returned
> > by dax_busy_page() and when the refcount is again checked in
> > ext4_break_layouts() => ___wait_var_event(), the waiting function
> > ext4_wait_dax_page() will never be called.  This means that
> > ext4_break_layouts() will still have 'retry' set to false, so we'll stop
> > looping and never check the refcount of other pages in this inode.
> > 
> > Instead, always continue looping as long as dax_layout_busy_page() gives us
> > a page which it found with an elevated refcount.
> > 
> > Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
> > Reviewed-by: Jan Kara <jack@...e.cz>
> 
> Ted - wondering if this one is still on your radar?

Resent the patch to Ted to catch more attention.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR