Re: [PATCH v2 11/18] xfs: Add xfs_attr3_leaf helper functions

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Aug 09, 2019 at 02:37:19PM -0700, Allison Collins wrote:
> And new helper functions xfs_attr3_leaf_flag_is_set and
> xfs_attr3_leaf_flagsflipped.  These routines check to see
> if xfs_attr3_leaf_setflag or xfs_attr3_leaf_flipflags have
> already been run.  We will need this later for delayed
> attributes since routines may be recalled several times
> when -EAGAIN is returned.
> 
> Signed-off-by: Allison Collins <allison.henderson@oracle.com>
> ---
>  fs/xfs/libxfs/xfs_attr_leaf.c | 78 +++++++++++++++++++++++++++++++++++++++++++
>  fs/xfs/libxfs/xfs_attr_leaf.h |  2 ++
>  2 files changed, 80 insertions(+)
> 
> diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c
> index 4a22ced..b2d5f62 100644
> --- a/fs/xfs/libxfs/xfs_attr_leaf.c
> +++ b/fs/xfs/libxfs/xfs_attr_leaf.c
> @@ -2729,6 +2729,34 @@ xfs_attr3_leaf_clearflag(
>  }
>  
>  /*
> + * Check if the INCOMPLETE flag on an entry in a leaf block is set.
> + */
> +int
> +xfs_attr3_leaf_flag_is_set(
> +	struct xfs_da_args		*args)

<urk> Please don't conflate error codes and a boolean predicate.  It
would be way too easy to do:

if (xfs_attr3_leaf_flag_is_set(&args)) {
	/* launch the nuculur missiles */
}

because there was a disk error and xfs_attr3_leaf_read fed us -EIO.
Either make the callers do the _read and pass the bp to this predicate,
or add a "bool *isset" outparam.

Second potential failure case:

error = xfs_attr3_leaf_flag_is_set(&args);
if (error) {
	/* bury all the whatever */
}

Wherein everything was actually fine, but instead someone incorrectly
freaked out and that's why my neighbors were running chainsaws at 11pm
last night.

> +{
> +	struct xfs_attr_leafblock	*leaf;
> +	struct xfs_attr_leaf_entry	*entry;
> +	struct xfs_buf			*bp;
> +	struct xfs_inode		*dp = args->dp;
> +	int				error = 0;
> +
> +	trace_xfs_attr_leaf_setflag(args);
> +
> +	/*
> +	 * Set up the operation.
> +	 */
> +	error = xfs_attr3_leaf_read(args->trans, dp, args->blkno, -1, &bp);
> +	if (error)
> +		return error;
> +
> +	leaf = bp->b_addr;
> +	entry = &xfs_attr3_leaf_entryp(leaf)[args->index];
> +
> +	return ((entry->flags & XFS_ATTR_INCOMPLETE) != 0);
> +}
> +
> +/*
>   * Set the INCOMPLETE flag on an entry in a leaf block.
>   */
>  int
> @@ -2890,3 +2918,53 @@ xfs_attr3_leaf_flipflags(
>  
>  	return error;
>  }
> +
> +/*
> + * On a leaf entry, check to see if the INCOMPLETE flag is cleared
> + * in args->blkno/index and set in args->blkno2/index2.
> + *
> + * Note that they could be in different blocks, or in the same block.
> + */
> +int
> +xfs_attr3_leaf_flagsflipped(
> +	struct xfs_da_args		*args)
> +{
> +	struct xfs_attr_leafblock	*leaf1;
> +	struct xfs_attr_leafblock	*leaf2;
> +	struct xfs_attr_leaf_entry	*entry1;
> +	struct xfs_attr_leaf_entry	*entry2;
> +	struct xfs_buf			*bp1;
> +	struct xfs_buf			*bp2;
> +	struct xfs_inode		*dp = args->dp;
> +	int				error = 0;
> +
> +	trace_xfs_attr_leaf_flipflags(args);
> +
> +	/*
> +	 * Read the block containing the "old" attr
> +	 */
> +	error = xfs_attr3_leaf_read(args->trans, dp, args->blkno, -1, &bp1);
> +	if (error)
> +		return error;
> +
> +	/*
> +	 * Read the block containing the "new" attr, if it is different
> +	 */
> +	if (args->blkno2 != args->blkno) {
> +		error = xfs_attr3_leaf_read(args->trans, args->dp, args->blkno2,
> +					   -1, &bp2);
> +		if (error)
> +			return error;
> +	} else {
> +		bp2 = bp1;
> +	}
> +
> +	leaf1 = bp1->b_addr;
> +	entry1 = &xfs_attr3_leaf_entryp(leaf1)[args->index];
> +
> +	leaf2 = bp2->b_addr;
> +	entry2 = &xfs_attr3_leaf_entryp(leaf2)[args->index2];
> +
> +	return (((entry1->flags & XFS_ATTR_INCOMPLETE) == 0) &&
> +		 (entry2->flags & XFS_ATTR_INCOMPLETE));

Same complaint here.

--D

> +}
> diff --git a/fs/xfs/libxfs/xfs_attr_leaf.h b/fs/xfs/libxfs/xfs_attr_leaf.h
> index be1f636..d6afe23 100644
> --- a/fs/xfs/libxfs/xfs_attr_leaf.h
> +++ b/fs/xfs/libxfs/xfs_attr_leaf.h
> @@ -54,7 +54,9 @@ int	xfs_attr3_leaf_to_shortform(struct xfs_buf *bp,
>  				   struct xfs_da_args *args, int forkoff);
>  int	xfs_attr3_leaf_clearflag(struct xfs_da_args *args);
>  int	xfs_attr3_leaf_setflag(struct xfs_da_args *args);
> +int	xfs_attr3_leaf_flag_is_set(struct xfs_da_args *args);
>  int	xfs_attr3_leaf_flipflags(struct xfs_da_args *args);
> +int	xfs_attr3_leaf_flagsflipped(struct xfs_da_args *args);
>  
>  /*
>   * Routines used for growing the Btree.
> -- 
> 2.7.4
>