Re: [PATCH] xfs: don't deplete the reserve pool when trying to shrink the fs

[Gao Xiang <hsiangkao@linux.alibaba.com>]

On 2023/5/23 21:46, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> Every now and then, xfs/168 fails with this logged in dmesg:
> 
> Reserve blocks depleted! Consider increasing reserve pool size.
> EXPERIMENTAL online shrink feature in use. Use at your own risk!
> Per-AG reservation for AG 1 failed.  Filesystem may run out of space.
> Per-AG reservation for AG 1 failed.  Filesystem may run out of space.
> Error -28 reserving per-AG metadata reserve pool.
> Corruption of in-memory data (0x8) detected at xfs_ag_shrink_space+0x23c/0x3b0 [xfs] (fs/xfs/libxfs/xfs_ag.c:1007).  Shutting down filesystem.
> 
> It's silly to deplete the reserved blocks pool just to shrink the
> filesystem, particularly since the fs goes down after that.
> 
> Fixes: fb2fc1720185 ("xfs: support shrinking unused space in the last AG")

Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>

[ These months I have no more slots for XFS, will go back later
   after some ongoing feature development is done. ]

Thanks,
Gao Xiang


> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> ---
>   fs/xfs/xfs_fsops.c |   10 +++++++---
>   1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
> index 13851c0d640b..5f00527b8065 100644
> --- a/fs/xfs/xfs_fsops.c
> +++ b/fs/xfs/xfs_fsops.c
> @@ -140,9 +140,13 @@ xfs_growfs_data_private(
>   		return -EINVAL;
>   	}
>   
> -	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_growdata,
> -			(delta > 0 ? XFS_GROWFS_SPACE_RES(mp) : -delta), 0,
> -			XFS_TRANS_RESERVE, &tp);
> +	if (delta > 0)
> +		error = xfs_trans_alloc(mp, &M_RES(mp)->tr_growdata,
> +				XFS_GROWFS_SPACE_RES(mp), 0, XFS_TRANS_RESERVE,
> +				&tp);
> +	else
> +		error = xfs_trans_alloc(mp, &M_RES(mp)->tr_growdata, -delta, 0,
> +				0, &tp);
>   	if (error)
>   		return error;
>