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Re: [PATCH v5 2/10] xfs: Add support FALLOC_FL_COLLAPSE_RANGE for falloc

To: Namjae Jeon <linkinjeon@xxxxxxxxx>
Subject: Re: [PATCH v5 2/10] xfs: Add support FALLOC_FL_COLLAPSE_RANGE for fallocate
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Mon, 24 Feb 2014 08:22:31 +1100
Cc: viro@xxxxxxxxxxxxxxxxxx, bpm@xxxxxxx, tytso@xxxxxxx, adilger.kernel@xxxxxxxxx, jack@xxxxxxx, mtk.manpages@xxxxxxxxx, lczerner@xxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Namjae Jeon <namjae.jeon@xxxxxxxxxxx>, Ashish Sangwan <a.sangwan@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1392741475-20063-1-git-send-email-linkinjeon@xxxxxxxxx>
References: <1392741475-20063-1-git-send-email-linkinjeon@xxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Wed, Feb 19, 2014 at 01:37:55AM +0900, Namjae Jeon wrote:
> From: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
> 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@xxxxxxxxxxx>
> Signed-off-by: Ashish Sangwan <a.sangwan@xxxxxxxxxxx>
> +     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@xxxxxxxxxx>


Dave Chinner

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