Re: [PATCH 2/4] xfs: include inobt buffers in ifree tx log reservation

[Dave Chinner <david@fromorbit.com>]

On Mon, Nov 27, 2017 at 03:24:32PM -0500, Brian Foster wrote:
> The tr_ifree transaction handles inode unlinks and inode chunk
> frees. The current transaction calculation does not accurately
> reflect worst case changes to the inode btree, however. The inobt
> portion of the current transaction reservation only covers
> modification of a single inobt buffer (for the particular inode
> record). This is a historical artifact from the days before XFS
> supported full inode chunk removal.
> 
> When support for inode chunk removal was added in commit
> 254f6311ed1b ("Implement deletion of inode clusters in XFS."), the
> additional log reservation required for chunk removal was not added
> correctly. The new reservation only considered the header overhead
> of associated buffers rather than the full contents of the btrees
> and AGF and AGFL buffers affected by the transaction. The
> reservation for the free space btrees was subsequently fixed up in
> commit 5fe6abb82f76 ("Add space for inode and allocation btrees to
> ITRUNCATE log reservation"), but the res. for full inobt joins has
> never been added.
> 
> Update xfs_calc_ifree_reservation() to include a full inobt join in
> the reservation calculation. Refactor the undocumented +2 blocks for
> the AGF and AGFL buffers into the appropriate place so they are
> accounted as sectors (not FSBs) and update the associated comments.
> 
> Signed-off-by: Brian Foster <bfoster@redhat.com>
> ---
>  fs/xfs/libxfs/xfs_trans_resv.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_trans_resv.c b/fs/xfs/libxfs/xfs_trans_resv.c
> index 6bd916bd35e2..4cd7cd1e60da 100644
> --- a/fs/xfs/libxfs/xfs_trans_resv.c
> +++ b/fs/xfs/libxfs/xfs_trans_resv.c
> @@ -490,10 +490,10 @@ xfs_calc_symlink_reservation(
>  /*
>   * In freeing an inode we can modify:
>   *    the inode being freed: inode size
> - *    the super block free inode counter: sector size
> + *    the super block free inode counter, AGF and AGFL: sector size
>   *    the agi hash list and counters: sector size
> - *    the inode btree entry: block size
>   *    the on disk inode before ours in the agi hash list: inode cluster size
> + *    the inode chunk is marked stale (headers only)
>   *    the inode btree: max depth * blocksize
>   *    the allocation btrees: 2 trees * (max depth - 1) * block size
>   *    the finobt (record insertion, removal or modification)
> @@ -504,12 +504,11 @@ xfs_calc_ifree_reservation(
>  {
>  	return XFS_DQUOT_LOGRES(mp) +
>  		xfs_calc_inode_res(mp, 1) +

 *    the inode being freed: inode size

> -		xfs_calc_buf_res(1, mp->m_sb.sb_sectsize) +
> -		xfs_calc_buf_res(1, XFS_FSB_TO_B(mp, 1)) +
> +		xfs_calc_buf_res(3, mp->m_sb.sb_sectsize) +

 *    the super block free inode counter, AGF and AGFL: sector size

		[missing, hidden in calc_iunlink_remove]

 *    the agi hash list and counters: sector size

>  		xfs_calc_iunlink_remove_reservation(mp) +

 *    the on disk inode before ours in the agi hash list: inode cluster size

		[missing]

 *    on-disk inode to log the di_next_unlinked: inode cluster size

Yes, check the xfs_iunlink_remove() code - we can log two inode
cluster buffers there: the one prior to us in the unlinked list,
and ours to reset the di_next_unlinked pointer to
null. IOWs, xfs_calc_iunlink_remove_reservation() needs to take into
account /2/ inode cluster buffers, not one.

>  		xfs_calc_buf_res(1, 0) +

No idea what this is.

> -		xfs_calc_buf_res(2 + mp->m_ialloc_blks +
> -				 mp->m_in_maxlevels, 0) +
> +		xfs_calc_buf_res(mp->m_ialloc_blks, 0) +

 *    the inode chunk is marked stale (headers only)

> +		xfs_calc_buf_res(mp->m_in_maxlevels, XFS_FSB_TO_B(mp, 1)) +

  *    the inode btree: max depth * blocksize

>  		xfs_calc_buf_res(xfs_allocfree_log_count(mp, 1),
>  				 XFS_FSB_TO_B(mp, 1)) +
  *    the allocation btrees: 2 trees * (max depth - 1) * block size

>  		xfs_calc_finobt_res(mp, 0, 1);

  *    the finobt (record insertion, removal or modification)

The rest look fine.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com