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Re: [PATCH] xfs: check if device support discard in xfs_ioc_trim()

To: Lukas Czerner <lczerner@xxxxxxxxxx>
Subject: Re: [PATCH] xfs: check if device support discard in xfs_ioc_trim()
From: Alex Elder <aelder@xxxxxxx>
Date: Tue, 15 Feb 2011 12:54:06 -0600
Cc: xfs@xxxxxxxxxxx, hch@xxxxxxxxxxxxx
In-reply-to: <1297789656-6088-1-git-send-email-lczerner@xxxxxxxxxx>
References: <1297789656-6088-1-git-send-email-lczerner@xxxxxxxxxx>
Reply-to: aelder@xxxxxxx
On Tue, 2011-02-15 at 18:07 +0100, Lukas Czerner wrote:
> Right now we, are relying on the fact that when we attempt to actually do
> the discard, blkdev_issue_discar() returns -EOPNOTSUPP and the user is
> informed that the device does not support discard.
> 
> However, in the case where the we do not hit any suitable free extent to
> trim in FITRIM code, it will finish without any error. This is very
> confusing, because it seems that FITRIM was successful even though the
> device does not actually supports discard.
> 
> Solution: Check for the discard support before attempt to search for
> free extents.
> 
> Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
> ---
>  fs/xfs/linux-2.6/xfs_discard.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/xfs/linux-2.6/xfs_discard.c b/fs/xfs/linux-2.6/xfs_discard.c
> index 05201ae..d61611c 100644
> --- a/fs/xfs/linux-2.6/xfs_discard.c
> +++ b/fs/xfs/linux-2.6/xfs_discard.c
> @@ -152,6 +152,8 @@ xfs_ioc_trim(
>  
>       if (!capable(CAP_SYS_ADMIN))
>               return -XFS_ERROR(EPERM);
> +     if (!blk_queue_discard(q))
> +             return -XFS_ERROR(EOPNOTSUPP);
>       if (copy_from_user(&range, urange, sizeof(range)))
>               return -XFS_ERROR(EFAULT);
>  

Looks good.

Reviewed-by: Alex Elder <aelder@xxxxxxx>


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