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Date: Wed, 8 Aug 2018 10:53:39 +0200
From: Jan Kara <jack@...e.cz>
To: Dave Jiang <dave.jiang@...el.com>
Cc: 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 2/2] [PATCH] xfs: Close race between direct IO and
xfs_break_layouts()
On Tue 07-08-18 15:11:43, Dave Jiang wrote:
> This patch is the duplicate of ross's fix for ext4 for xfs.
>
> 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
> xfs_break_layouts() => ___wait_var_event(), the waiting function
> xfs_wait_dax_page() will never be called. This means that
> xfs_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: Dave Jiang <dave.jiang@...el.com>
The patch looks good to me. You can add:
Reviewed-by: Jan Kara <jack@...e.cz>
Just one minor nit below:
> @@ -746,9 +744,10 @@ xfs_break_dax_layouts(
> if (!page)
> return 0;
>
> + *did_unlock = true;
I think it would be more understandable to name the argument of
xfs_break_dax_layouts() as 'retry' instead of 'did_unlock' as it's not
about unlocking anymore.
Honza
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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