linux-kernel - Re: [PATCH v5 2/10] xfs: Add support FALLOC_FL_COLLAPSE

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Date:	Mon, 24 Feb 2014 08:22:31 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Namjae Jeon <linkinjeon@...il.com>
Cc:	viro@...iv.linux.org.uk, bpm@....com, tytso@....edu,
	adilger.kernel@...ger.ca, jack@...e.cz, mtk.manpages@...il.com,
	lczerner@...hat.com, linux-fsdevel@...r.kernel.org,
	xfs@....sgi.com, linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Namjae Jeon <namjae.jeon@...sung.com>,
	Ashish Sangwan <a.sangwan@...sung.com>
Subject: Re: [PATCH v5 2/10] xfs: Add support FALLOC_FL_COLLAPSE_RANGE for
 fallocate

On Wed, Feb 19, 2014 at 01:37:55AM +0900, Namjae Jeon wrote:
> From: Namjae Jeon <namjae.jeon@...sung.com>
> 
> This patch implements fallocate's FALLOC_FL_COLLAPSE_RANGE for XFS.
> 
> The semantics of this flag are following:
> 1) It collapses the range lying between offset and length by removing any data
>    blocks which are present in this range and than updates all the logical
>    offsets of extents beyond "offset + len" to nullify the hole created by
>    removing blocks. In short, it does not leave a hole.
> 2) It should be used exclusively. No other fallocate flag in combination.
> 3) Offset and length supplied to fallocate should be fs block size aligned
>    in case of xfs and ext4.
> 4) Collaspe range does not work beyond i_size.
> 
> Signed-off-by: Namjae Jeon <namjae.jeon@...sung.com>
> Signed-off-by: Ashish Sangwan <a.sangwan@...sung.com>
.....
> +	while (!error && !done) {
> +		tp = xfs_trans_alloc(mp, XFS_TRANS_DIOSTRAT);
> +		tp->t_flags |= XFS_TRANS_RESERVE;

This probably shouldn't use XFS_TRANS_RESERVE. If we are at ENOSPC,
then the operation simply fails. Yes, we've already punched the
hole, so we shouldn't get ENOSPC here, but I don't think it's worth
dipping into the reserve pool as it has much more important uses...

You don' tneed to resent the entire patch for this - I can remove it
directly myself....

Otherwise it looks good, so consider it

Reviewed-by: Dave Chinner <dchinner@...hat.com>

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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