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Re: ***** SUSPECTED SPAM ***** [RFD 06/17] xfs: partial inode chunk allo

To: xfs@xxxxxxxxxxx
Subject: Re: ***** SUSPECTED SPAM ***** [RFD 06/17] xfs: partial inode chunk allocation
From: Brian Foster <bfoster@xxxxxxxxxx>
Date: Tue, 13 Aug 2013 18:07:12 -0400
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1376313607-28133-7-git-send-email-david@xxxxxxxxxxxxx>
References: <1376313607-28133-1-git-send-email-david@xxxxxxxxxxxxx> <1376313607-28133-7-git-send-email-david@xxxxxxxxxxxxx>
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On 08/12/2013 09:19 AM, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
> 
> When a filesystem ages or when certain workloads dominate the storage capacity
> of the filesystem, it can become difficult to find contiguous free space in 
> the
> filesystem and hence inode allocation can fail long before the filesystem is 
> out
> of space.
> 
...
> ---

The issue outlined above is something that was observed with workloads
running against swift (object storage) on top of gluster (distributed
storage) on top of XFS with larger than default inode sizes (512b, 1k).
Unfortunately, I don't have any specific data to describe the workload.
If I recall correctly, the end result was free space fragmentation
leading to premature ENOSPC on inode allocation due to unavailability of
sufficiently sized extents for inode chunks.

After a brief irc conversation, Dave suggested that the immediately
previous item:

[RFD 05/17] xfs: introduce a free inode allocation btree

... tie in with and precede this partial chunk allocation work, so I'm
going to try to pick off this new free inode btree and partial chunk
allocation work. Just a heads up to the list to try and avoid any
duplicate effort. :)

Thanks again for writing this up, Dave.

Brian

>  fs/xfs/xfs_ialloc_btree.h | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_ialloc_btree.h b/fs/xfs/xfs_ialloc_btree.h
> index 3ac36b76..75ee794 100644
> --- a/fs/xfs/xfs_ialloc_btree.h
> +++ b/fs/xfs/xfs_ialloc_btree.h
> @@ -48,7 +48,9 @@ static inline xfs_inofree_t xfs_inobt_maskn(int i, int n)
>   */
>  typedef struct xfs_inobt_rec {
>       __be32          ir_startino;    /* starting inode number */
> -     __be32          ir_freecount;   /* count of free inodes (set bits) */
> +     __be16          ir_alloc_mask;
> +     __u8            ir_pad;
> +     __u8            ir_freecount;
>       __be64          ir_free;        /* free inode mask */
>  } xfs_inobt_rec_t;
>  
> 

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