Re: [PATCH v3 1/3] xfs: zero entire directory data block header region at init

[Darrick J. Wong]

On Sat, Apr 11, 2026 at 03:24:13PM +0100, Yuto Ohnuki wrote:
> xfs_dir3_data_init currently zeroes only the xfs_dir3_blk_hdr portion of
> the directory data block header, then manually initializes the bestfree
> entries in a loop. This leaves the pad field in xfs_dir3_data_hdr
> uninitialized and requires explicit zeroing of each bestfree slot.
> 
> Zero the entire header region (geo->data_entry_offset bytes)
> unconditionally before setting individual fields. This covers all
> current and future header fields, all padding (implicit and explicit),
> and the bestfree array, so the manual zeroing loop for bestfree can be
> removed.
> 
> Suggested-by: Dave Chinner <dgc@xxxxxxxxxx>
> Signed-off-by: Yuto Ohnuki <ytohnuki@xxxxxxxxxx>

Seems reasonable to me to zero the entire head including the bestfree
areas.

Reviewed-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>

--D

> ---
>  fs/xfs/libxfs/xfs_dir2_data.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_dir2_data.c b/fs/xfs/libxfs/xfs_dir2_data.c
> index 80ba94f51e5c..35ff119aa84b 100644
> --- a/fs/xfs/libxfs/xfs_dir2_data.c
> +++ b/fs/xfs/libxfs/xfs_dir2_data.c
> @@ -728,7 +728,6 @@ xfs_dir3_data_init(
>  	struct xfs_dir2_data_unused	*dup;
>  	struct xfs_dir2_data_free 	*bf;
>  	int				error;
> -	int				i;
>  
>  	/*
>  	 * Get the buffer set up for the block.
> @@ -741,13 +740,16 @@ xfs_dir3_data_init(
>  	xfs_trans_buf_set_type(tp, bp, XFS_BLFT_DIR_DATA_BUF);
>  
>  	/*
> -	 * Initialize the header.
> +	 * Initialize the whole directory header region to zero
> +	 * so that all padding, bestfree entries, and any
> +	 * future header fields are clean.
>  	 */
>  	hdr = bp->b_addr;
> +	memset(hdr, 0, geo->data_entry_offset);
> +
>  	if (xfs_has_crc(mp)) {
>  		struct xfs_dir3_blk_hdr *hdr3 = bp->b_addr;
>  
> -		memset(hdr3, 0, sizeof(*hdr3));
>  		hdr3->magic = cpu_to_be32(XFS_DIR3_DATA_MAGIC);
>  		hdr3->blkno = cpu_to_be64(xfs_buf_daddr(bp));
>  		hdr3->owner = cpu_to_be64(args->owner);
> @@ -759,10 +761,6 @@ xfs_dir3_data_init(
>  	bf = xfs_dir2_data_bestfree_p(mp, hdr);
>  	bf[0].offset = cpu_to_be16(geo->data_entry_offset);
>  	bf[0].length = cpu_to_be16(geo->blksize - geo->data_entry_offset);
> -	for (i = 1; i < XFS_DIR2_DATA_FD_COUNT; i++) {
> -		bf[i].length = 0;
> -		bf[i].offset = 0;
> -	}
>  
>  	/*
>  	 * Set up an unused entry for the block's body.
> -- 
> 2.50.1
> 
> 
> 
> 
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