xfs: Add xfs_attr_set_deferred and xfs_attr_remove_deferred

These routines set up and queue a new deferred attribute operations.
These functions are meant to be called by any routine needing to
initiate a deferred attribute operation as opposed to the existing
inline operations. New helper function xfs_attr_item_init also added.

Finally enable delayed attributes in xfs_attr_set and xfs_attr_remove.
Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/libxfs/xfs_attr.c

@@ -25,6 +25,7 @@
 #include "xfs_trans_space.h"
 #include "xfs_trace.h"
 #include "xfs_attr_item.h"
+#include "xfs_log.h"
 
 struct kmem_cache		*xfs_attri_cache;
 struct kmem_cache		*xfs_attrd_cache;
@@ -729,6 +730,7 @@ xfs_attr_set(
 	int			error, local;
 	int			rmt_blks = 0;
 	unsigned int		total;
+	int			delayed = xfs_has_larp(mp);
 
 	if (xfs_is_shutdown(dp->i_mount))
 		return -EIO;
@@ -785,13 +787,19 @@ xfs_attr_set(
 		rmt_blks = xfs_attr3_rmt_blocks(mp, XFS_XATTR_SIZE_MAX);
 	}
 
+	if (delayed) {
+		error = xfs_attr_use_log_assist(mp);
+		if (error)
+			return error;
+	}
+
 	/*
 	 * Root fork attributes can use reserved data blocks for this
 	 * operation if necessary
 	 */
 	error = xfs_trans_alloc_inode(dp, &tres, total, 0, rsvd, &args->trans);
 	if (error)
-		return error;
+		goto drop_incompat;
 
 	if (args->value || xfs_inode_hasattr(dp)) {
 		error = xfs_iext_count_may_overflow(dp, XFS_ATTR_FORK,
@@ -812,9 +820,10 @@ xfs_attr_set(
 		if (error != -ENOATTR && error != -EEXIST)
 			goto out_trans_cancel;
 
-		error = xfs_attr_set_args(args);
+		error = xfs_attr_set_deferred(args);
 		if (error)
 			goto out_trans_cancel;
+
 		/* shortform attribute has already been committed */
 		if (!args->trans)
 			goto out_unlock;
@@ -822,7 +831,7 @@ xfs_attr_set(
 		if (error != -EEXIST)
 			goto out_trans_cancel;
 
-		error = xfs_attr_remove_args(args);
+		error = xfs_attr_remove_deferred(args);
 		if (error)
 			goto out_trans_cancel;
 	}
@@ -844,6 +853,9 @@ xfs_attr_set(
 	error = xfs_trans_commit(args->trans);
 out_unlock:
 	xfs_iunlock(dp, XFS_ILOCK_EXCL);
+drop_incompat:
+	if (delayed)
+		xlog_drop_incompat_feat(mp->m_log);
 	return error;
 
 out_trans_cancel:
@@ -886,6 +898,58 @@ xfs_attrd_destroy_cache(void)
 	xfs_attrd_cache = NULL;
 }
 
+STATIC int
+xfs_attr_item_init(
+	struct xfs_da_args	*args,
+	unsigned int		op_flags,	/* op flag (set or remove) */
+	struct xfs_attr_item	**attr)		/* new xfs_attr_item */
+{
+
+	struct xfs_attr_item	*new;
+
+	new = kmem_zalloc(sizeof(struct xfs_attr_item), KM_NOFS);
+	new->xattri_op_flags = op_flags;
+	new->xattri_dac.da_args = args;
+
+	*attr = new;
+	return 0;
+}
+
+/* Sets an attribute for an inode as a deferred operation */
+int
+xfs_attr_set_deferred(
+	struct xfs_da_args	*args)
+{
+	struct xfs_attr_item	*new;
+	int			error = 0;
+
+	error = xfs_attr_item_init(args, XFS_ATTR_OP_FLAGS_SET, &new);
+	if (error)
+		return error;
+
+	xfs_defer_add(args->trans, XFS_DEFER_OPS_TYPE_ATTR, &new->xattri_list);
+
+	return 0;
+}
+
+/* Removes an attribute for an inode as a deferred operation */
+int
+xfs_attr_remove_deferred(
+	struct xfs_da_args	*args)
+{
+
+	struct xfs_attr_item	*new;
+	int			error;
+
+	error  = xfs_attr_item_init(args, XFS_ATTR_OP_FLAGS_REMOVE, &new);
+	if (error)
+		return error;
+
+	xfs_defer_add(args->trans, XFS_DEFER_OPS_TYPE_ATTR, &new->xattri_list);
+
+	return 0;
+}
+
 /*========================================================================
  * External routines when attribute list is inside the inode
  *========================================================================*/

fs/xfs/libxfs/xfs_attr.h

@@ -525,6 +525,8 @@ bool xfs_attr_namecheck(const void *name, size_t length);
 void xfs_delattr_context_init(struct xfs_delattr_context *dac,
 			      struct xfs_da_args *args);
 int xfs_attr_calc_size(struct xfs_da_args *args, int *local);
+int xfs_attr_set_deferred(struct xfs_da_args *args);
+int xfs_attr_remove_deferred(struct xfs_da_args *args);
 
 extern struct kmem_cache	*xfs_attri_cache;
 extern struct kmem_cache	*xfs_attrd_cache;

fs/xfs/xfs_log.c

@@ -3877,3 +3877,44 @@ xlog_drop_incompat_feat(
 {
 	up_read(&log->l_incompat_users);
 }
+
+/*
+ * Get permission to use log-assisted atomic exchange of file extents.
+ *
+ * Callers must not be running any transactions or hold any inode locks, and
+ * they must release the permission by calling xlog_drop_incompat_feat
+ * when they're done.
+ */
+int
+xfs_attr_use_log_assist(
+	struct xfs_mount	*mp)
+{
+	int			error = 0;
+
+	/*
+	 * Protect ourselves from an idle log clearing the logged xattrs log
+	 * incompat feature bit.
+	 */
+	xlog_use_incompat_feat(mp->m_log);
+
+	/*
+	 * If log-assisted xattrs are already enabled, the caller can use the
+	 * log assisted swap functions with the log-incompat reference we got.
+	 */
+	if (xfs_sb_version_haslogxattrs(&mp->m_sb))
+		return 0;
+
+	/* Enable log-assisted xattrs. */
+	error = xfs_add_incompat_log_feature(mp,
+			XFS_SB_FEAT_INCOMPAT_LOG_XATTRS);
+	if (error)
+		goto drop_incompat;
+
+	xfs_warn_once(mp,
+"EXPERIMENTAL logged extended attributes feature added. Use at your own risk!");
+
+	return 0;
+drop_incompat:
+	xlog_drop_incompat_feat(mp->m_log);
+	return error;
+}

fs/xfs/xfs_log.h

@@ -153,5 +153,6 @@ bool	  xlog_force_shutdown(struct xlog *log, uint32_t shutdown_flags);
 
 void xlog_use_incompat_feat(struct xlog *log);
 void xlog_drop_incompat_feat(struct xlog *log);
+int xfs_attr_use_log_assist(struct xfs_mount *mp);
 
 #endif	/* __XFS_LOG_H__ */