xfs
[Top] [All Lists]

Re: [PATCH 2/6] XFS: handle hole punching via fallocate properly

To: Josef Bacik <josef@xxxxxxxxxx>
Subject: Re: [PATCH 2/6] XFS: handle hole punching via fallocate properly
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Tue, 9 Nov 2010 12:22:54 +1100
Cc: linux-kernel@xxxxxxxxxxxxxxx, linux-btrfs@xxxxxxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, joel.becker@xxxxxxxxxx, cmm@xxxxxxxxxx, cluster-devel@xxxxxxxxxx
In-reply-to: <1289248327-16308-2-git-send-email-josef@xxxxxxxxxx>
References: <1289248327-16308-1-git-send-email-josef@xxxxxxxxxx> <1289248327-16308-2-git-send-email-josef@xxxxxxxxxx>
User-agent: Mutt/1.5.20 (2009-06-14)
On Mon, Nov 08, 2010 at 03:32:03PM -0500, Josef Bacik wrote:
> This patch simply allows XFS to handle the hole punching flag in fallocate
> properly.  I've tested this with a little program that does a bunch of random
> hole punching with FL_KEEP_SIZE and without it to make sure it does the right
> thing.  Thanks,
> 
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxx>
> ---
>  fs/xfs/linux-2.6/xfs_iops.c |   12 +++++++++---
>  1 files changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/xfs/linux-2.6/xfs_iops.c b/fs/xfs/linux-2.6/xfs_iops.c
> index 96107ef..99df347 100644
> --- a/fs/xfs/linux-2.6/xfs_iops.c
> +++ b/fs/xfs/linux-2.6/xfs_iops.c
> @@ -516,6 +516,7 @@ xfs_vn_fallocate(
>       loff_t          new_size = 0;
>       xfs_flock64_t   bf;
>       xfs_inode_t     *ip = XFS_I(inode);
> +     int             cmd = XFS_IOC_RESVSP;
>  
>       /* preallocation on directories not yet supported */
>       error = -ENODEV;
> @@ -528,17 +529,22 @@ xfs_vn_fallocate(
>  
>       xfs_ilock(ip, XFS_IOLOCK_EXCL);
>  
> +     if (mode & FALLOC_FL_PUNCH_HOLE)
> +             cmd = XFS_IOC_UNRESVSP;
> +
>       /* check the new inode size is valid before allocating */
>       if (!(mode & FALLOC_FL_KEEP_SIZE) &&
>           offset + len > i_size_read(inode)) {
> -             new_size = offset + len;
> +             if (cmd == XFS_IOC_UNRESVSP)
> +                     new_size = offset;
> +             else
> +                     new_size = offset + len;

What semantic is FALLOC_FL_KEEP_SIZE supposed to convey during a
hole punch? Doesn't this just turn the hole punch operation into
a truncate? If so, what's the point of punching the hole when you
can just call ftruncate() to get the same result?

I'd suggest that FALLOC_FL_PUNCH_HOLE should, by definition, not
change the file size, and have no option to be able to change it.
This needs to be defined and documented - can you include a man
page update in this series that defines the expected behaviour
of FALLOC_FL_PUNCH_HOLE?

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

<Prev in Thread] Current Thread [Next in Thread>