linux-ext4 - Re: [RFC PATCH V2 10/12] fs/xfs: Fix truncate up

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Date:   Mon, 13 Jan 2020 16:40:47 -0800
From:   Ira Weiny <ira.weiny@...el.com>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     linux-kernel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>,
        Christoph Hellwig <hch@....de>,
        "Theodore Y. Ts'o" <tytso@....edu>, Jan Kara <jack@...e.cz>,
        linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [RFC PATCH V2 10/12] fs/xfs: Fix truncate up

On Mon, Jan 13, 2020 at 02:27:55PM -0800, Darrick J. Wong wrote:
> On Fri, Jan 10, 2020 at 11:29:40AM -0800, ira.weiny@...el.com wrote:
> > From: Ira Weiny <ira.weiny@...el.com>
> > 
> > When zeroing the end of a file we must account for bytes contained in
> > the final page which are past EOF.
> > 
> > Extend the range passed to iomap_zero_range() to reach LLONG_MAX which
> > will include all bytes of the final page.
> > 
> > Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> > ---
> >  fs/xfs/xfs_iops.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> > index a2f2604c3187..a34b04e8ac9c 100644
> > --- a/fs/xfs/xfs_iops.c
> > +++ b/fs/xfs/xfs_iops.c
> > @@ -910,7 +910,7 @@ xfs_setattr_size(
> >  	 */
> >  	if (newsize > oldsize) {
> >  		trace_xfs_zero_eof(ip, oldsize, newsize - oldsize);
> > -		error = iomap_zero_range(inode, oldsize, newsize - oldsize,
> > +		error = iomap_zero_range(inode, oldsize, LLONG_MAX - oldsize,
> 
> Huh?  Won't this cause the file size to be set to LLONG_MAX?

Not as I understand the code.  But as I said in the cover I am not 100% sure of
this fix.

>From what I can tell xfs_ioctl_setattr_dax_invalidate() should invalidate the
mappings and the page cache and the traces I have indicate that the DAX mode
is not changing or was properly held off.

Any other suggestions as to the problem are welcome.

Ira


> 
> --D
> 
> >  				&did_zeroing, &xfs_buffered_write_iomap_ops);
> >  	} else {
> >  		error = iomap_truncate_page(inode, newsize, &did_zeroing,
> > -- 
> > 2.21.0
> >