Re: [PATCH] xfs: set xefi_discard when creating a deferred agfl free log intent item

[Brian Foster <bfoster@redhat.com>]

On Thu, Oct 22, 2020 at 11:46:49AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Make sure that we actually initialize xefi_discard when we're scheduling
> a deferred free of an AGFL block.  This was (eventually) found by the
> UBSAN while I was banging on realtime rmap problems, but it exists in
> the upstream codebase.  While we're at it, rearrange the structure to
> reduce the struct size from 64 to 56 bytes.
> 
> Fixes: fcb762f5de2e ("xfs: add bmapi nodiscard flag")
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---

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

>  fs/xfs/libxfs/xfs_alloc.c |    1 +
>  fs/xfs/libxfs/xfs_bmap.h  |    2 +-
>  2 files changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> index 852b536551b5..15640015be9d 100644
> --- a/fs/xfs/libxfs/xfs_alloc.c
> +++ b/fs/xfs/libxfs/xfs_alloc.c
> @@ -2467,6 +2467,7 @@ xfs_defer_agfl_block(
>  	new->xefi_startblock = XFS_AGB_TO_FSB(mp, agno, agbno);
>  	new->xefi_blockcount = 1;
>  	new->xefi_oinfo = *oinfo;
> +	new->xefi_skip_discard = false;
>  
>  	trace_xfs_agfl_free_defer(mp, agno, 0, agbno, 1);
>  
> diff --git a/fs/xfs/libxfs/xfs_bmap.h b/fs/xfs/libxfs/xfs_bmap.h
> index e1bd484e5548..6747e97a7949 100644
> --- a/fs/xfs/libxfs/xfs_bmap.h
> +++ b/fs/xfs/libxfs/xfs_bmap.h
> @@ -52,9 +52,9 @@ struct xfs_extent_free_item
>  {
>  	xfs_fsblock_t		xefi_startblock;/* starting fs block number */
>  	xfs_extlen_t		xefi_blockcount;/* number of blocks in extent */
> +	bool			xefi_skip_discard;
>  	struct list_head	xefi_list;
>  	struct xfs_owner_info	xefi_oinfo;	/* extent owner */
> -	bool			xefi_skip_discard;
>  };
>  
>  #define	XFS_BMAP_MAX_NMAP	4
>