Re: [PATCH 09/16] xfs: remote xattr removal in xfs_attr_set_iter() is conditional

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On Thu, 2022-04-14 at 19:44 +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
> 
> We may not have a remote value for the old xattr we have to remove,
> so skip over the remote value removal states and go straight to
> the xattr name removal in the leaf/node block.
> 
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
Ok, I can follow it.  I may try and think of a new way to try and
illustrate it though as it is not nearly as linear as it used to be,
but I don't think that's a bad thing.  

Reviewed-by: Allison Henderson<allison.henderson@xxxxxxxxxx>
> ---
>  fs/xfs/libxfs/xfs_attr.c | 59 ++++++++++++++++++++----------------
> ----
>  fs/xfs/libxfs/xfs_attr.h |  8 +++---
>  fs/xfs/xfs_trace.h       |  4 +--
>  3 files changed, 36 insertions(+), 35 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index c72f98794bb3..8762d3a0605a 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -510,15 +510,14 @@ xfs_attr_set_iter(
>  		/*
>  		 * We must "flip" the incomplete flags on the "new" and
> "old"
>  		 * attribute/value pairs so that one disappears and one
> appears
> -		 * atomically.  Then we must remove the "old"
> attribute/value
> -		 * pair.
> +		 * atomically.
>  		 */
>  		error = xfs_attr3_leaf_flipflags(args);
>  		if (error)
>  			return error;
>  		/*
> -		 * Commit the flag value change and start the next
> trans
> -		 * in series at REMOVE_OLD.
> +		 * We must commit the flag value change now to make it
> atomic
> +		 * and then we can start the next trans in series at
> REMOVE_OLD.
>  		 */
>  		error = -EAGAIN;
>  		attr->xattri_dela_state++;
> @@ -527,41 +526,43 @@ xfs_attr_set_iter(
>  	case XFS_DAS_LEAF_REMOVE_OLD:
>  	case XFS_DAS_NODE_REMOVE_OLD:
>  		/*
> -		 * Dismantle the "old" attribute/value pair by removing
> a
> -		 * "remote" value (if it exists).
> +		 * If we have a remote attr, start the process of
> removing it
> +		 * by invalidating any cached buffers.
> +		 *
> +		 * If we don't have a remote attr, we skip the remote
> block
> +		 * removal state altogether with a second state
> increment.
>  		 */
>  		xfs_attr_restore_rmt_blk(args);
> -		error = xfs_attr_rmtval_invalidate(args);
> -		if (error)
> -			return error;
> -
> -		attr->xattri_dela_state++;
> -		fallthrough;
> -	case XFS_DAS_RM_LBLK:
> -	case XFS_DAS_RM_NBLK:
>  		if (args->rmtblkno) {
> -			error = xfs_attr_rmtval_remove(attr);
> -			if (error == -EAGAIN)
> -				trace_xfs_attr_set_iter_return(
> -					attr->xattri_dela_state, args-
> >dp);
> +			error = xfs_attr_rmtval_invalidate(args);
>  			if (error)
>  				return error;
> -
> -			attr->xattri_dela_state = XFS_DAS_RD_LEAF;
> -			trace_xfs_attr_set_iter_return(attr-
> >xattri_dela_state,
> -						       args->dp);
> -			return -EAGAIN;
> +		} else {
> +			attr->xattri_dela_state++;
>  		}
>  
> +		attr->xattri_dela_state++;
> +		goto next_state;
> +
> +	case XFS_DAS_LEAF_REMOVE_RMT:
> +	case XFS_DAS_NODE_REMOVE_RMT:
> +		error = xfs_attr_rmtval_remove(attr);
> +		if (error == -EAGAIN)
> +			break;
> +		if (error)
> +			return error;
> +
>  		/*
> -		 * This is the end of the shared leaf/node sequence. We
> need
> -		 * to continue at the next state in the sequence, but
> we can't
> -		 * easily just fall through. So we increment to the
> next state
> -		 * and then jump back to switch statement to evaluate
> the next
> -		 * state correctly.
> +		 * We've finished removing the remote attr blocks, so
> commit the
> +		 * transaction and move on to removing the attr name
> from the
> +		 * leaf/node block. Removing the attr might require a
> full
> +		 * transaction reservation for btree block freeing, so
> we
> +		 * can't do that in the same transaction where we
> removed the
> +		 * remote attr blocks.
>  		 */
> +		error = -EAGAIN;
>  		attr->xattri_dela_state++;
> -		goto next_state;
> +		break;
>  
>  	case XFS_DAS_RD_LEAF:
>  		/*
> diff --git a/fs/xfs/libxfs/xfs_attr.h b/fs/xfs/libxfs/xfs_attr.h
> index a4ff0a2305d6..18e157bf19cb 100644
> --- a/fs/xfs/libxfs/xfs_attr.h
> +++ b/fs/xfs/libxfs/xfs_attr.h
> @@ -456,7 +456,7 @@ enum xfs_delattr_state {
>  	XFS_DAS_LEAF_ALLOC_RMT,		/* We are allocating remote
> blocks */
>  	XFS_DAS_LEAF_REPLACE,		/* Perform replace ops on a
> leaf */
>  	XFS_DAS_LEAF_REMOVE_OLD,	/* Start removing old attr from leaf
> */
> -	XFS_DAS_RM_LBLK,		/* A rename is removing leaf blocks
> */
> +	XFS_DAS_LEAF_REMOVE_RMT,	/* A rename is removing remote blocks
> */
>  	XFS_DAS_RD_LEAF,		/* Read in the new leaf */
>  
>  	/* Node state set sequence, must match leaf state above */
> @@ -464,7 +464,7 @@ enum xfs_delattr_state {
>  	XFS_DAS_NODE_ALLOC_RMT,		/* We are allocating remote
> blocks */
>  	XFS_DAS_NODE_REPLACE,		/* Perform replace ops on a
> node */
>  	XFS_DAS_NODE_REMOVE_OLD,	/* Start removing old attr from node
> */
> -	XFS_DAS_RM_NBLK,		/* A rename is removing node blocks
> */
> +	XFS_DAS_NODE_REMOVE_RMT,	/* A rename is removing remote blocks
> */
>  	XFS_DAS_CLR_FLAG,		/* Clear incomplete flag */
>  
>  	XFS_DAS_DONE,			/* finished operation */
> @@ -482,13 +482,13 @@ enum xfs_delattr_state {
>  	{ XFS_DAS_LEAF_ALLOC_RMT,	"XFS_DAS_LEAF_ALLOC_RMT" }, \
>  	{ XFS_DAS_LEAF_REPLACE,		"XFS_DAS_LEAF_REPLACE" }, \
>  	{ XFS_DAS_LEAF_REMOVE_OLD,	"XFS_DAS_LEAF_REMOVE_OLD" },
> \
> -	{ XFS_DAS_RM_LBLK,		"XFS_DAS_RM_LBLK" }, \
> +	{ XFS_DAS_LEAF_REMOVE_RMT,	"XFS_DAS_LEAF_REMOVE_RMT" },
> \
>  	{ XFS_DAS_RD_LEAF,		"XFS_DAS_RD_LEAF" }, \
>  	{ XFS_DAS_NODE_SET_RMT,		"XFS_DAS_NODE_SET_RMT" }, \
>  	{ XFS_DAS_NODE_ALLOC_RMT,	"XFS_DAS_NODE_ALLOC_RMT" },  \
>  	{ XFS_DAS_NODE_REPLACE,		"XFS_DAS_NODE_REPLACE" },  \
>  	{ XFS_DAS_NODE_REMOVE_OLD,	"XFS_DAS_NODE_REMOVE_OLD" },
> \
> -	{ XFS_DAS_RM_NBLK,		"XFS_DAS_RM_NBLK" }, \
> +	{ XFS_DAS_NODE_REMOVE_RMT,	"XFS_DAS_NODE_REMOVE_RMT" },
> \
>  	{ XFS_DAS_CLR_FLAG,		"XFS_DAS_CLR_FLAG" }, \
>  	{ XFS_DAS_DONE,			"XFS_DAS_DONE" }
>  
> diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
> index a4b99c7f8ef0..91852b9721e4 100644
> --- a/fs/xfs/xfs_trace.h
> +++ b/fs/xfs/xfs_trace.h
> @@ -4109,13 +4109,13 @@ TRACE_DEFINE_ENUM(XFS_DAS_LEAF_SET_RMT);
>  TRACE_DEFINE_ENUM(XFS_DAS_LEAF_ALLOC_RMT);
>  TRACE_DEFINE_ENUM(XFS_DAS_LEAF_REPLACE);
>  TRACE_DEFINE_ENUM(XFS_DAS_LEAF_REMOVE_OLD);
> -TRACE_DEFINE_ENUM(XFS_DAS_RM_LBLK);
> +TRACE_DEFINE_ENUM(XFS_DAS_LEAF_REMOVE_RMT);
>  TRACE_DEFINE_ENUM(XFS_DAS_RD_LEAF);
>  TRACE_DEFINE_ENUM(XFS_DAS_NODE_SET_RMT);
>  TRACE_DEFINE_ENUM(XFS_DAS_NODE_ALLOC_RMT);
>  TRACE_DEFINE_ENUM(XFS_DAS_NODE_REPLACE);
>  TRACE_DEFINE_ENUM(XFS_DAS_NODE_REMOVE_OLD);
> -TRACE_DEFINE_ENUM(XFS_DAS_RM_NBLK);
> +TRACE_DEFINE_ENUM(XFS_DAS_NODE_REMOVE_RMT);
>  TRACE_DEFINE_ENUM(XFS_DAS_CLR_FLAG);
>  
>  DECLARE_EVENT_CLASS(xfs_das_state_class,




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