Re: [PATCH v6 16/16] xfs: Add delay ready attr set routines

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

On Sat, Jan 18, 2020 at 03:50:35PM -0700, Allison Collins wrote:
> This patch modifies the attr set routines to be delay ready. This means
> they no longer roll or commit transactions, but instead return -EAGAIN
> to have the calling routine roll and refresh the transaction.  In this
> series, xfs_attr_set_args has become xfs_attr_set_iter, which uses a
> state machine like switch to keep track of where it was when EAGAIN was
> returned.
> 
> Part of xfs_attr_leaf_addname has been factored out into a new helper
> function xfs_attr_leaf_try_add to allow transaction cycling between the
> two routines.
> 
> Two new helper functions have been added: xfs_attr_rmtval_set_init and
> xfs_attr_rmtval_set_blk.  They provide a subset of logic similar to
> xfs_attr_rmtval_set, but they store the current block in the delay attr
> context to allow the caller to roll the transaction between allocations.
> This helps to simplify and consolidate code used by
> xfs_attr_leaf_addname and xfs_attr_node_addname
> 
> Finally, xfs_attr_set_args has become a simple loop to refresh the
> transaction until the operation is completed.
> 
> Signed-off-by: Allison Collins <allison.henderson@oracle.com>
> ---
>  fs/xfs/libxfs/xfs_attr.c        | 347 +++++++++++++++++++++++++---------------
>  fs/xfs/libxfs/xfs_attr.h        |   1 +
>  fs/xfs/libxfs/xfs_attr_remote.c |  67 +++++++-
>  fs/xfs/libxfs/xfs_attr_remote.h |   4 +
>  fs/xfs/libxfs/xfs_da_btree.h    |  13 ++
>  5 files changed, 301 insertions(+), 131 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index 92929ad..02a7f55 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -58,6 +58,7 @@ STATIC int xfs_attr_node_hasname(xfs_da_args_t *args,
>  				 struct xfs_da_state **state);
>  STATIC int xfs_attr_fillstate(xfs_da_state_t *state);
>  STATIC int xfs_attr_refillstate(xfs_da_state_t *state);
> +STATIC int xfs_attr_leaf_try_add(struct xfs_da_args *args, struct xfs_buf *bp);
>  
>  
>  STATIC int
> @@ -259,9 +260,86 @@ int
>  xfs_attr_set_args(
>  	struct xfs_da_args	*args)
>  {
> +	int			error = 0;
> +	int			err2 = 0;
> +	struct xfs_buf		*leaf_bp = NULL;
> +
> +	do {
> +		error = xfs_attr_set_iter(args, &leaf_bp);
> +		if (error && error != -EAGAIN)
> +			goto out;
> +
> +		if (args->dac.flags & XFS_DAC_FINISH_TRANS) {
> +			args->dac.flags &= ~XFS_DAC_FINISH_TRANS;
> +
> +			err2 = xfs_defer_finish(&args->trans);
> +			if (err2) {
> +				error = err2;
> +				goto out;
> +			}
> +		}
> +
> +		err2 = xfs_trans_roll_inode(&args->trans, args->dp);
> +		if (err2) {
> +			error = err2;
> +			goto out;
> +		}
> +
> +		if (leaf_bp) {
> +			xfs_trans_bjoin(args->trans, leaf_bp);
> +			xfs_trans_bhold(args->trans, leaf_bp);
> +		}
> +
> +	} while (error == -EAGAIN);
> +
> +out:
> +	return error;
> +}
> +
> +/*
> + * Set the attribute specified in @args.
> + * This routine is meant to function as a delayed operation, and may return
> + * -EAGAIN when the transaction needs to be rolled.  Calling functions will need
> + * to handle this, and recall the function until a successful error code is
> + * returned.
> + */
> +int
> +xfs_attr_set_iter(
> +	struct xfs_da_args	*args,
> +	struct xfs_buf          **leaf_bp)
> +{
>  	struct xfs_inode	*dp = args->dp;
> -	struct xfs_buf          *leaf_bp = NULL;
> -	int			error, error2 = 0;
> +	int			error = 0;
> +	int			sf_size;
> +
> +	/* State machine switch */
> +	switch (args->dac.dela_state) {
> +	case XFS_DAS_SF_TO_LEAF:
> +		goto sf_to_leaf;
> +	case XFS_DAS_ALLOC_LEAF:
> +	case XFS_DAS_FLIP_LFLAG:
> +	case XFS_DAS_FOUND_LBLK:
> +		goto leaf;
> +	case XFS_DAS_FOUND_NBLK:
> +	case XFS_DAS_FLIP_NFLAG:
> +	case XFS_DAS_ALLOC_NODE:
> +	case XFS_DAS_LEAF_TO_NODE:
> +		goto node;
> +	default:

Er... do these need to ASSERT on invalid states?  e.g. if somehow we end
up with XFS_DAS_RM_SHRINK, we ought to blow up loudly, right?


> +		break;
> +	}
> +
> +	/*
> +	 * New inodes may not have an attribute fork yet. So set the attribute
> +	 * fork appropriately
> +	 */
> +	if (XFS_IFORK_Q((args->dp)) == 0) {
> +		sf_size = sizeof(struct xfs_attr_sf_hdr) +
> +		     XFS_ATTR_SF_ENTSIZE_BYNAME(args->name.len, args->valuelen);
> +		xfs_bmap_set_attrforkoff(args->dp, sf_size, NULL);
> +		args->dp->i_afp = kmem_zone_zalloc(xfs_ifork_zone, 0);
> +		args->dp->i_afp->if_flags = XFS_IFEXTENTS;
> +	}
>  
>  	/*
>  	 * If the attribute list is non-existent or a shortform list, proceed to
> @@ -272,22 +350,20 @@ xfs_attr_set_args(
>  	    (dp->i_d.di_aformat == XFS_DINODE_FMT_EXTENTS &&
>  	     dp->i_d.di_anextents == 0)))
>  		goto sf_to_leaf;
> -
>  	/*
>  	 * Try to add the attr to the attribute list in the inode.
>  	 */
>  	error = xfs_attr_try_sf_addname(dp, args);
> -	if (error != -ENOSPC) {
> -		error2 = xfs_trans_commit(args->trans);
> -		args->trans = NULL;
> -		return error ? error : error2;

Where does this commit go?

> -	}
> +
> +	/* Should only be 0, -EEXIST or ENOSPC */
> +	if (error != -ENOSPC)
> +		return error;
>  
>  	/*
>  	 * It won't fit in the shortform, transform to a leaf block.
>  	 * GROT: another possible req'mt for a double-split btree op.
>  	 */
> -	error = xfs_attr_shortform_to_leaf(args, &leaf_bp);
> +	error = xfs_attr_shortform_to_leaf(args, leaf_bp);
>  	if (error)
>  		return error;
>  
> @@ -295,42 +371,47 @@ xfs_attr_set_args(
>  	 * Prevent the leaf buffer from being unlocked so that a
>  	 * concurrent AIL push cannot grab the half-baked leaf
>  	 * buffer and run into problems with the write verifier.
> -	 * Once we're done rolling the transaction we can release
> -	 * the hold and add the attr to the leaf.
>  	 */
> -	xfs_trans_bhold(args->trans, leaf_bp);
> -	error = xfs_defer_finish(&args->trans);
> -	xfs_trans_bhold_release(args->trans, leaf_bp);
> -	if (error) {
> -		xfs_trans_brelse(args->trans, leaf_bp);
> -		return error;
> -	}
> +	xfs_trans_bhold(args->trans, *leaf_bp);
> +	args->dac.flags |= XFS_DAC_FINISH_TRANS;
> +	args->dac.dela_state = XFS_DAS_SF_TO_LEAF;
> +	return -EAGAIN;
>  
>  sf_to_leaf:
>  
> -	if (xfs_bmap_one_block(dp, XFS_ATTR_FORK)) {
> -		error = xfs_attr_leaf_addname(args);
> -		if (error != -ENOSPC)
> -			return error;
> -
> -		/*
> -		 * Commit that transaction so that the node_addname()
> -		 * call can manage its own transactions.
> -		 */
> -		error = xfs_defer_finish(&args->trans);
> -		if (error)
> -			return error;
> +	/*
> +	 * After a shortform to leaf conversion, we need to hold the leaf and
> +	 * cylce out the transaction.  When we get back, we need to release
> +	 * the leaf.
> +	 */
> +	if (*leaf_bp != NULL) {
> +		xfs_trans_brelse(args->trans, *leaf_bp);
> +		*leaf_bp = NULL;
> +	}
>  
> -		/*
> -		 * Commit the current trans (including the inode) and
> -		 * start a new one.
> -		 */
> -		error = xfs_trans_roll_inode(&args->trans, dp);
> -		if (error)
> +	if (xfs_bmap_one_block(dp, XFS_ATTR_FORK)) {
> +		error = xfs_attr_leaf_try_add(args, *leaf_bp);
> +		switch (error) {
> +		case -ENOSPC:
> +			args->dac.flags |= XFS_DAC_FINISH_TRANS;
> +			args->dac.dela_state = XFS_DAS_LEAF_TO_NODE;
> +			return -EAGAIN;
> +		case 0:
> +			args->dac.dela_state = XFS_DAS_FOUND_LBLK;
> +			return -EAGAIN;
> +		default:
>  			return error;
> -
> +		}
> +leaf:
> +		error = xfs_attr_leaf_addname(args);
> +		if (error == -ENOSPC) {
> +			args->dac.dela_state = XFS_DAS_LEAF_TO_NODE;
> +			return -EAGAIN;
> +		}
> +		return error;
>  	}
> -
> +	args->dac.dela_state = XFS_DAS_LEAF_TO_NODE;
> +node:
>  	error = xfs_attr_node_addname(args);
>  	return error;
>  }
> @@ -759,27 +840,28 @@ xfs_attr_leaf_try_add(
>   *
>   * This leaf block cannot have a "remote" value, we only call this routine
>   * if bmap_one_block() says there is only one block (ie: no remote blks).
> + *
> + * This routine is meant to function as a delayed operation, and may return
> + * -EAGAIN when the transaction needs to be rolled.  Calling functions will need
> + * to handle this, and recall the function until a successful error code is
> + * returned.
>   */
>  STATIC int
>  xfs_attr_leaf_addname(struct xfs_da_args	*args)
>  {
> -	int			error, forkoff;
>  	struct xfs_buf		*bp = NULL;
> +	int			error, forkoff;
>  	struct xfs_inode	*dp = args->dp;
>  
> -	trace_xfs_attr_leaf_addname(args);
> -
> -	error = xfs_attr_leaf_try_add(args, bp);
> -	if (error)
> -		return error;
> -
> -	/*
> -	 * Commit the transaction that added the attr name so that
> -	 * later routines can manage their own transactions.
> -	 */
> -	error = xfs_trans_roll_inode(&args->trans, dp);
> -	if (error)
> -		return error;
> +	/* State machine switch */
> +	switch (args->dac.dela_state) {
> +	case XFS_DAS_FLIP_LFLAG:
> +		goto flip_flag;
> +	case XFS_DAS_ALLOC_LEAF:
> +		goto alloc_leaf;
> +	default:
> +		break;
> +	}
>  
>  	/*
>  	 * If there was an out-of-line value, allocate the blocks we
> @@ -788,7 +870,28 @@ xfs_attr_leaf_addname(struct xfs_da_args	*args)
>  	 * maximum size of a transaction and/or hit a deadlock.
>  	 */
>  	if (args->rmtblkno > 0) {
> -		error = xfs_attr_rmtval_set(args);
> +
> +		/* Open coded xfs_attr_rmtval_set without trans handling */
> +		error = xfs_attr_rmtval_set_init(args);
> +		if (error)
> +			return error;
> +
> +		/*
> +		 * Roll through the "value", allocating blocks on disk as
> +		 * required.
> +		 */
> +alloc_leaf:
> +		while (args->dac.blkcnt > 0) {
> +			error = xfs_attr_rmtval_set_blk(args);
> +			if (error)
> +				return error;
> +
> +			args->dac.flags |= XFS_DAC_FINISH_TRANS;
> +			args->dac.dela_state = XFS_DAS_ALLOC_LEAF;
> +			return -EAGAIN;
> +		}
> +
> +		error = xfs_attr_rmtval_set_value(args);
>  		if (error)
>  			return error;
>  	}
> @@ -807,13 +910,10 @@ xfs_attr_leaf_addname(struct xfs_da_args	*args)
>  		error = xfs_attr3_leaf_flipflags(args);
>  		if (error)
>  			return error;
> -		/*
> -		 * Commit the flag value change and start the next trans in
> -		 * series.
> -		 */
> -		error = xfs_trans_roll_inode(&args->trans, args->dp);
> -		if (error)
> -			return error;
> +
> +		args->dac.dela_state = XFS_DAS_FLIP_LFLAG;
> +		return -EAGAIN;
> +flip_flag:
>  
>  		/*
>  		 * Dismantle the "old" attribute/value pair by removing
> @@ -844,34 +944,17 @@ xfs_attr_leaf_addname(struct xfs_da_args	*args)
>  		/*
>  		 * If the result is small enough, shrink it all into the inode.
>  		 */
> -		if ((forkoff = xfs_attr_shortform_allfit(bp, dp))) {
> +		forkoff = xfs_attr_shortform_allfit(bp, dp);
> +		if (forkoff)
>  			error = xfs_attr3_leaf_to_shortform(bp, args, forkoff);
> -			/* bp is gone due to xfs_da_shrink_inode */
> -			if (error)
> -				return error;
> -			error = xfs_defer_finish(&args->trans);
> -			if (error)
> -				return error;
> -		}
>  
> -		/*
> -		 * Commit the remove and start the next trans in series.
> -		 */
> -		error = xfs_trans_roll_inode(&args->trans, dp);
> +		args->dac.flags |= XFS_DAC_FINISH_TRANS;
>  
>  	} else if (args->rmtblkno > 0) {
>  		/*
>  		 * Added a "remote" value, just clear the incomplete flag.
>  		 */
>  		error = xfs_attr3_leaf_clearflag(args);
> -		if (error)
> -			return error;
> -
> -		/*
> -		 * Commit the flag value change and start the next trans in
> -		 * series.
> -		 */
> -		error = xfs_trans_roll_inode(&args->trans, args->dp);
>  	}
>  	return error;
>  }
> @@ -1020,16 +1103,22 @@ xfs_attr_node_hasname(
>   *
>   * "Remote" attribute values confuse the issue and atomic rename operations
>   * add a whole extra layer of confusion on top of that.
> + *
> + * This routine is meant to function as a delayed operation, and may return
> + * -EAGAIN when the transaction needs to be rolled.  Calling functions will need
> + * to handle this, and recall the function until a successful error code is
> + *returned.
>   */
>  STATIC int
>  xfs_attr_node_addname(
>  	struct xfs_da_args	*args)
>  {
> -	struct xfs_da_state	*state;
> +	struct xfs_da_state	*state = NULL;
>  	struct xfs_da_state_blk	*blk;
>  	struct xfs_inode	*dp;
>  	struct xfs_mount	*mp;
> -	int			retval, error;
> +	int			retval = 0;
> +	int			error = 0;
>  
>  	trace_xfs_attr_node_addname(args);
>  
> @@ -1038,7 +1127,19 @@ xfs_attr_node_addname(
>  	 */
>  	dp = args->dp;
>  	mp = dp->i_mount;
> -restart:
> +
> +	/* State machine switch */
> +	switch (args->dac.dela_state) {
> +	case XFS_DAS_FLIP_NFLAG:
> +		goto flip_flag;
> +	case XFS_DAS_FOUND_NBLK:
> +		goto found_nblk;
> +	case XFS_DAS_ALLOC_NODE:
> +		goto alloc_node;
> +	default:
> +		break;
> +	}
> +
>  	/*
>  	 * Search to see if name already exists, and get back a pointer
>  	 * to where it should go.
> @@ -1088,19 +1189,13 @@ xfs_attr_node_addname(
>  			error = xfs_attr3_leaf_to_node(args);
>  			if (error)
>  				goto out;
> -			error = xfs_defer_finish(&args->trans);
> -			if (error)
> -				goto out;
>  
>  			/*
> -			 * Commit the node conversion and start the next
> -			 * trans in the chain.
> +			 * Restart routine from the top.  No need to set  the
> +			 * state

*OH*, dela_state == 0 does not mean "do not use delayed attrs", we're
switching /all/ users to delayed attrs.  Urk.

>  			 */
> -			error = xfs_trans_roll_inode(&args->trans, dp);
> -			if (error)
> -				goto out;
> -
> -			goto restart;
> +			args->dac.flags |= XFS_DAC_FINISH_TRANS;
> +			return -EAGAIN;
>  		}
>  
>  		/*
> @@ -1112,9 +1207,7 @@ xfs_attr_node_addname(
>  		error = xfs_da3_split(state);
>  		if (error)
>  			goto out;
> -		error = xfs_defer_finish(&args->trans);
> -		if (error)
> -			goto out;
> +		args->dac.flags |= XFS_DAC_FINISH_TRANS;
>  	} else {
>  		/*
>  		 * Addition succeeded, update Btree hashvals.
> @@ -1129,13 +1222,9 @@ xfs_attr_node_addname(
>  	xfs_da_state_free(state);
>  	state = NULL;
>  
> -	/*
> -	 * Commit the leaf addition or btree split and start the next
> -	 * trans in the chain.
> -	 */
> -	error = xfs_trans_roll_inode(&args->trans, dp);
> -	if (error)
> -		goto out;
> +	args->dac.dela_state = XFS_DAS_FOUND_NBLK;
> +	return -EAGAIN;
> +found_nblk:
>  
>  	/*
>  	 * If there was an out-of-line value, allocate the blocks we
> @@ -1144,7 +1233,27 @@ xfs_attr_node_addname(
>  	 * maximum size of a transaction and/or hit a deadlock.
>  	 */
>  	if (args->rmtblkno > 0) {
> -		error = xfs_attr_rmtval_set(args);
> +		/* Open coded xfs_attr_rmtval_set without trans handling */
> +		error = xfs_attr_rmtval_set_init(args);
> +		if (error)
> +			return error;
> +
> +		/*
> +		 * Roll through the "value", allocating blocks on disk as
> +		 * required.
> +		 */
> +alloc_node:
> +		while (args->dac.blkcnt > 0) {
> +			error = xfs_attr_rmtval_set_blk(args);
> +			if (error)
> +				return error;
> +
> +			args->dac.flags |= XFS_DAC_FINISH_TRANS;
> +			args->dac.dela_state = XFS_DAS_ALLOC_NODE;
> +			return -EAGAIN;
> +		}
> +
> +		error = xfs_attr_rmtval_set_value(args);
>  		if (error)
>  			return error;
>  	}
> @@ -1167,10 +1276,9 @@ xfs_attr_node_addname(
>  		 * Commit the flag value change and start the next trans in
>  		 * series
>  		 */
> -		error = xfs_trans_roll_inode(&args->trans, args->dp);
> -		if (error)
> -			goto out;
> -
> +		args->dac.dela_state = XFS_DAS_FLIP_NFLAG;
> +		return -EAGAIN;
> +flip_flag:
>  		/*
>  		 * Dismantle the "old" attribute/value pair by removing
>  		 * a "remote" value (if it exists).
> @@ -1199,7 +1307,6 @@ xfs_attr_node_addname(
>  		error = xfs_da3_node_lookup_int(state, &retval);
>  		if (error)
>  			goto out;
> -
>  		/*
>  		 * Remove the name and update the hashvals in the tree.
>  		 */
> @@ -1207,7 +1314,6 @@ xfs_attr_node_addname(
>  		ASSERT(blk->magic == XFS_ATTR_LEAF_MAGIC);
>  		error = xfs_attr3_leaf_remove(blk->bp, args);
>  		xfs_da3_fixhashpath(state, &state->path);
> -
>  		/*
>  		 * Check to see if the tree needs to be collapsed.
>  		 */
> @@ -1215,18 +1321,9 @@ xfs_attr_node_addname(
>  			error = xfs_da3_join(state);
>  			if (error)
>  				goto out;
> -			error = xfs_defer_finish(&args->trans);
> -			if (error)
> -				goto out;
> -		}
> -
> -		/*
> -		 * Commit and start the next trans in the chain.
> -		 */
> -		error = xfs_trans_roll_inode(&args->trans, dp);
> -		if (error)
> -			goto out;
>  
> +			args->dac.flags |= XFS_DAC_FINISH_TRANS;
> +		}
>  	} else if (args->rmtblkno > 0) {
>  		/*
>  		 * Added a "remote" value, just clear the incomplete flag.
> @@ -1234,14 +1331,6 @@ xfs_attr_node_addname(
>  		error = xfs_attr3_leaf_clearflag(args);
>  		if (error)
>  			goto out;
> -
> -		 /*
> -		  * Commit the flag value change and start the next trans in
> -		  * series.
> -		  */
> -		error = xfs_trans_roll_inode(&args->trans, args->dp);
> -		if (error)
> -			goto out;
>  	}
>  	retval = error = 0;
>  
> diff --git a/fs/xfs/libxfs/xfs_attr.h b/fs/xfs/libxfs/xfs_attr.h
> index ea873a5..f450d8c 100644
> --- a/fs/xfs/libxfs/xfs_attr.h
> +++ b/fs/xfs/libxfs/xfs_attr.h
> @@ -152,6 +152,7 @@ int xfs_attr_get(struct xfs_inode *ip, struct xfs_name *name,
>  int xfs_attr_set(struct xfs_inode *dp, struct xfs_name *name,
>  		 unsigned char *value, int valuelen, int flags);
>  int xfs_attr_set_args(struct xfs_da_args *args);
> +int xfs_attr_set_iter(struct xfs_da_args *args, struct xfs_buf **leaf_bp);
>  int xfs_attr_remove(struct xfs_inode *dp, struct xfs_name *name, int flags);
>  int xfs_has_attr(struct xfs_da_args *args);
>  int xfs_attr_remove_args(struct xfs_da_args *args);
> diff --git a/fs/xfs/libxfs/xfs_attr_remote.c b/fs/xfs/libxfs/xfs_attr_remote.c
> index f2ee0b8..ad4f14a 100644
> --- a/fs/xfs/libxfs/xfs_attr_remote.c
> +++ b/fs/xfs/libxfs/xfs_attr_remote.c
> @@ -428,7 +428,7 @@ xfs_attr_rmtval_get(
>   * Find a "hole" in the attribute address space large enough for us to drop the
>   * new attribute's value into
>   */
> -STATIC int
> +int
>  xfs_attr_rmt_find_hole(
>  	struct xfs_da_args	*args)
>  {
> @@ -455,7 +455,7 @@ xfs_attr_rmt_find_hole(
>  	return 0;
>  }
>  
> -STATIC int
> +int
>  xfs_attr_rmtval_set_value(
>  	struct xfs_da_args	*args)
>  {
> @@ -588,6 +588,69 @@ xfs_attr_rmtval_set(
>  }
>  
>  /*
> + * Find a hole for the attr and store it in the delayed attr context.  This
> + * initializes the context to roll through allocating an attr extent for a
> + * delayed attr operation
> + */
> +int
> +xfs_attr_rmtval_set_init(
> +	struct xfs_da_args	*args)
> +{
> +	struct xfs_bmbt_irec	*map = &args->dac.map;
> +	int error;
> +
> +	args->dac.lblkno = 0;
> +	args->dac.lfileoff = 0;
> +	args->dac.blkcnt = 0;
> +	args->rmtblkcnt = 0;
> +	args->rmtblkno = 0;
> +	memset(map, 0, sizeof(struct xfs_bmbt_irec));
> +
> +	error = xfs_attr_rmt_find_hole(args);
> +	if (error)
> +		return error;
> +
> +	args->dac.blkcnt = args->rmtblkcnt;
> +	args->dac.lblkno = args->rmtblkno;
> +
> +	return error;
> +}
> +
> +/*
> + * Write one block of the value associated with an attribute into the
> + * out-of-line buffer that we have defined for it. This is similar to a subset
> + * of xfs_attr_rmtval_set, but records the current block to the delayed attr
> + * context, and leaves transaction handling to the caller.
> + */
> +int
> +xfs_attr_rmtval_set_blk(
> +	struct xfs_da_args	*args)
> +{
> +	struct xfs_inode	*dp = args->dp;
> +	struct xfs_bmbt_irec	*map = &args->dac.map;
> +	int nmap;
> +	int error;
> +
> +	nmap = 1;
> +	error = xfs_bmapi_write(args->trans, dp,
> +		  (xfs_fileoff_t)args->dac.lblkno,
> +		  args->dac.blkcnt, XFS_BMAPI_ATTRFORK,
> +		  args->total, map, &nmap);
> +	if (error)
> +		return error;
> +
> +	ASSERT(nmap == 1);
> +	ASSERT((map->br_startblock != DELAYSTARTBLOCK) &&
> +	       (map->br_startblock != HOLESTARTBLOCK));
> +
> +	/* roll attribute extent map forwards */
> +	args->dac.lblkno += map->br_blockcount;
> +	args->dac.blkcnt -= map->br_blockcount;
> +
> +	return 0;
> +}
> +
> +/*
>   * Remove the value associated with an attribute by deleting the
>   * out-of-line buffer that it is stored on.
>   */
> diff --git a/fs/xfs/libxfs/xfs_attr_remote.h b/fs/xfs/libxfs/xfs_attr_remote.h
> index 7ab3770..ab03519 100644
> --- a/fs/xfs/libxfs/xfs_attr_remote.h
> +++ b/fs/xfs/libxfs/xfs_attr_remote.h
> @@ -13,4 +13,8 @@ int xfs_attr_rmtval_set(struct xfs_da_args *args);
>  int xfs_attr_rmtval_remove(struct xfs_da_args *args);
>  int xfs_attr_rmtval_invalidate(struct xfs_da_args *args);
>  int xfs_attr_rmtval_unmap(struct xfs_da_args *args);
> +int xfs_attr_rmt_find_hole(struct xfs_da_args *args);
> +int xfs_attr_rmtval_set_value(struct xfs_da_args *args);
> +int xfs_attr_rmtval_set_blk(struct xfs_da_args *args);
> +int xfs_attr_rmtval_set_init(struct xfs_da_args *args);
>  #endif /* __XFS_ATTR_REMOTE_H__ */
> diff --git a/fs/xfs/libxfs/xfs_da_btree.h b/fs/xfs/libxfs/xfs_da_btree.h
> index 7fc87da..9943062 100644
> --- a/fs/xfs/libxfs/xfs_da_btree.h
> +++ b/fs/xfs/libxfs/xfs_da_btree.h
> @@ -55,6 +55,14 @@ enum xfs_dacmp {
>  enum xfs_delattr_state {
>  	XFS_DAS_RM_SHRINK	= 1, /* We are shrinking the tree */
>  	XFS_DAS_RM_NODE_BLKS	= 2, /* We are removing node blocks */
> +	XFS_DAS_SF_TO_LEAF	= 3, /* Converted short form to leaf */
> +	XFS_DAS_FOUND_LBLK	= 4, /* We found leaf blk for attr */
> +	XFS_DAS_LEAF_TO_NODE	= 5, /* Converted leaf to node */
> +	XFS_DAS_FOUND_NBLK	= 6, /* We found node blk for attr */
> +	XFS_DAS_ALLOC_LEAF	= 7, /* We are allocating leaf blocks */
> +	XFS_DAS_FLIP_LFLAG	= 8, /* Flipped leaf INCOMPLETE attr flag */
> +	XFS_DAS_ALLOC_NODE	= 9, /* We are allocating node blocks */
> +	XFS_DAS_FLIP_NFLAG	= 10,/* Flipped node INCOMPLETE attr flag */

We've definitely reached the point where a state diagram would be
helpful.  Can you go from any of the RM_ states to the ones that you've
just added?

The new state machine code in last two patches would be a lot easier to
review if I could look down from above instead of up from the XFS_DAS
values and goto labels.  I /think/ it looks sane, but I'm only 20%
confident of that statement.

--D

>  };
>  
>  /*
> @@ -66,8 +74,13 @@ enum xfs_delattr_state {
>   * Context used for keeping track of delayed attribute operations
>   */
>  struct xfs_delattr_context {
> +	struct xfs_bmbt_irec	map;
> +	struct xfs_buf		*leaf_bp;
> +	xfs_fileoff_t		lfileoff;
>  	struct xfs_da_state	*da_state;
>  	struct xfs_da_state_blk *blk;
> +	xfs_dablk_t		lblkno;
> +	int			blkcnt;
>  	int			flags;
>  	enum xfs_delattr_state	dela_state;
>  };
> -- 
> 2.7.4
>