Re: [PATCH 30/30] xfs: remove xfs_inobp_check()

[Brian Foster <bfoster@redhat.com>]

On Thu, Jun 04, 2020 at 05:46:06PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> This debug code is called on every xfs_iflush() call, which then
> checks every inode in the buffer for non-zero unlinked list field.
> Hence it checks every inode in the cluster buffer every time a
> single inode on that cluster it flushed. This is resulting in:
> 
> -   38.91%     5.33%  [kernel]  [k] xfs_iflush
>    - 17.70% xfs_iflush
>       - 9.93% xfs_inobp_check
>            4.36% xfs_buf_offset
> 
> 10% of the CPU time spent flushing inodes is repeatedly checking
> unlinked fields in the buffer. We don't need to do this.
> 
> The other place we call xfs_inobp_check() is
> xfs_iunlink_update_dinode(), and this is after we've done this
> assert for the agino we are about to write into that inode:
> 
> 	ASSERT(xfs_verify_agino_or_null(mp, agno, next_agino));
> 
> which means we've already checked that the agino we are about to
> write is not 0 on debug kernels. The inode buffer verifiers do
> everything else we need, so let's just remove this debug code.
> 
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---

Reviewed-by: Brian Foster <bfoster@redhat.com>

>  fs/xfs/libxfs/xfs_inode_buf.c | 24 ------------------------
>  fs/xfs/libxfs/xfs_inode_buf.h |  6 ------
>  fs/xfs/xfs_inode.c            |  2 --
>  3 files changed, 32 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
> index 1af97235785c8..6b6f67595bf4e 100644
> --- a/fs/xfs/libxfs/xfs_inode_buf.c
> +++ b/fs/xfs/libxfs/xfs_inode_buf.c
> @@ -20,30 +20,6 @@
>  
>  #include <linux/iversion.h>
>  
> -/*
> - * Check that none of the inode's in the buffer have a next
> - * unlinked field of 0.
> - */
> -#if defined(DEBUG)
> -void
> -xfs_inobp_check(
> -	xfs_mount_t	*mp,
> -	xfs_buf_t	*bp)
> -{
> -	int		i;
> -	xfs_dinode_t	*dip;
> -
> -	for (i = 0; i < M_IGEO(mp)->inodes_per_cluster; i++) {
> -		dip = xfs_buf_offset(bp, i * mp->m_sb.sb_inodesize);
> -		if (!dip->di_next_unlinked)  {
> -			xfs_alert(mp,
> -	"Detected bogus zero next_unlinked field in inode %d buffer 0x%llx.",
> -				i, (long long)bp->b_bn);
> -		}
> -	}
> -}
> -#endif
> -
>  /*
>   * If we are doing readahead on an inode buffer, we might be in log recovery
>   * reading an inode allocation buffer that hasn't yet been replayed, and hence
> diff --git a/fs/xfs/libxfs/xfs_inode_buf.h b/fs/xfs/libxfs/xfs_inode_buf.h
> index 865ac493c72a2..6b08b9d060c2e 100644
> --- a/fs/xfs/libxfs/xfs_inode_buf.h
> +++ b/fs/xfs/libxfs/xfs_inode_buf.h
> @@ -52,12 +52,6 @@ int	xfs_inode_from_disk(struct xfs_inode *ip, struct xfs_dinode *from);
>  void	xfs_log_dinode_to_disk(struct xfs_log_dinode *from,
>  			       struct xfs_dinode *to);
>  
> -#if defined(DEBUG)
> -void	xfs_inobp_check(struct xfs_mount *, struct xfs_buf *);
> -#else
> -#define	xfs_inobp_check(mp, bp)
> -#endif /* DEBUG */
> -
>  xfs_failaddr_t xfs_dinode_verify(struct xfs_mount *mp, xfs_ino_t ino,
>  			   struct xfs_dinode *dip);
>  xfs_failaddr_t xfs_inode_validate_extsize(struct xfs_mount *mp,
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index 931a483d5b316..9400c2e0b0c4a 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -2165,7 +2165,6 @@ xfs_iunlink_update_dinode(
>  	xfs_dinode_calc_crc(mp, dip);
>  	xfs_trans_inode_buf(tp, ibp);
>  	xfs_trans_log_buf(tp, ibp, offset, offset + sizeof(xfs_agino_t) - 1);
> -	xfs_inobp_check(mp, ibp);
>  }
>  
>  /* Set an in-core inode's unlinked pointer and return the old value. */
> @@ -3559,7 +3558,6 @@ xfs_iflush(
>  	xfs_iflush_fork(ip, dip, iip, XFS_DATA_FORK);
>  	if (XFS_IFORK_Q(ip))
>  		xfs_iflush_fork(ip, dip, iip, XFS_ATTR_FORK);
> -	xfs_inobp_check(mp, bp);
>  
>  	/*
>  	 * We've recorded everything logged in the inode, so we'd like to clear
> -- 
> 2.26.2.761.g0e0b3e54be
>