linux-kernel - Re: [PATCH v6] ext4: Add support FALLOC_FL_COLLAPSE

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Message-ID: <20140223214322.GF4317@dastard>
Date:	Mon, 24 Feb 2014 08:43:22 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Theodore Ts'o <tytso@....edu>, Namjae Jeon <linkinjeon@...il.com>,
	viro@...iv.linux.org.uk, bpm@....com, 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 v6] ext4: Add support FALLOC_FL_COLLAPSE_RANGE for
 fallocate

On Sat, Feb 22, 2014 at 12:09:30PM -0500, Theodore Ts'o wrote:
> On Fri, Feb 21, 2014 at 12:07:41AM +0900, Namjae Jeon wrote:
> > From: Namjae Jeon <namjae.jeon@...sung.com>
> > 
> > This patch implements fallocate's FALLOC_FL_COLLAPSE_RANGE for Ext4.
> > 
> > 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>
> > Tested-by: Dongsu Park <dongsu.park@...fitbricks.com>
> 
> In terms of how to get this upstream, it looks like if we do something
> like this, we can let this patch go via the ext4 tree and we don't
> need to worry about whether the vfs level changes have gone in our
> not.
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index ad13359..d7a78ed 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -46,6 +46,10 @@
>  
>  #include <trace/events/ext4.h>
>  
> +#ifndef FALLOC_FL_COLLAPSE_RANGE
> +#define FALLOC_FL_COLLAPSE_RANGE	0x08
> +#endif
> +
>  /*
>   * used by extent splitting.
>   */

You're more than welcome to do that, Ted. Just wait until we get the
VFS part into the XFS tree first ;)

Cheers,

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