xfs: create bmbt update intent log items

Create bmbt update intent/done log items to record redo information in
the log.  Because we roll transactions multiple times for reflink
operations, we also have to track the status of the metadata updates
that will be recorded in the post-roll transactions in case we crash
before committing the final transaction.  This mechanism enables log
recovery to finish what was already started.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 97 insertions, 0 deletions

diff --git a/fs/xfs/xfs_bmap_item.h b/fs/xfs/xfs_bmap_item.h
new file mode 100644
index 000000000000..57c13d3a9b03
--- /dev/null
+++ b/fs/xfs/xfs_bmap_item.h
@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2016 Oracle.  All Rights Reserved.
+ *
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+#ifndef	__XFS_BMAP_ITEM_H__
+#define	__XFS_BMAP_ITEM_H__
+
+/*
+ * There are (currently) two pairs of bmap btree redo item types: map & unmap.
+ * The common abbreviations for these are BUI (bmap update intent) and BUD
+ * (bmap update done).  The redo item type is encoded in the flags field of
+ * each xfs_map_extent.
+ *
+ * *I items should be recorded in the *first* of a series of rolled
+ * transactions, and the *D items should be recorded in the same transaction
+ * that records the associated bmbt updates.
+ *
+ * Should the system crash after the commit of the first transaction but
+ * before the commit of the final transaction in a series, log recovery will
+ * use the redo information recorded by the intent items to replay the
+ * bmbt metadata updates in the non-first transaction.
+ */
+
+/* kernel only BUI/BUD definitions */
+
+struct xfs_mount;
+struct kmem_zone;
+
+/*
+ * Max number of extents in fast allocation path.
+ */
+#define	XFS_BUI_MAX_FAST_EXTENTS	1
+
+/*
+ * Define BUI flag bits. Manipulated by set/clear/test_bit operators.
+ */
+#define	XFS_BUI_RECOVERED		1
+
+/*
+ * This is the "bmap update intent" log item.  It is used to log the fact that
+ * some reverse mappings need to change.  It is used in conjunction with the
+ * "bmap update done" log item described below.
+ *
+ * These log items follow the same rules as struct xfs_efi_log_item; see the
+ * comments about that structure (in xfs_extfree_item.h) for more details.
+ */
+struct xfs_bui_log_item {
+	struct xfs_log_item		bui_item;
+	atomic_t			bui_refcount;
+	atomic_t			bui_next_extent;
+	unsigned long			bui_flags;	/* misc flags */
+	struct xfs_bui_log_format	bui_format;
+};
+
+static inline size_t
+xfs_bui_log_item_sizeof(
+	unsigned int		nr)
+{
+	return offsetof(struct xfs_bui_log_item, bui_format) +
+			xfs_bui_log_format_sizeof(nr);
+}
+
+/*
+ * This is the "bmap update done" log item.  It is used to log the fact that
+ * some bmbt updates mentioned in an earlier bui item have been performed.
+ */
+struct xfs_bud_log_item {
+	struct xfs_log_item		bud_item;
+	struct xfs_bui_log_item		*bud_buip;
+	struct xfs_bud_log_format	bud_format;
+};
+
+extern struct kmem_zone	*xfs_bui_zone;
+extern struct kmem_zone	*xfs_bud_zone;
+
+struct xfs_bui_log_item *xfs_bui_init(struct xfs_mount *);
+struct xfs_bud_log_item *xfs_bud_init(struct xfs_mount *,
+		struct xfs_bui_log_item *);
+void xfs_bui_item_free(struct xfs_bui_log_item *);
+void xfs_bui_release(struct xfs_bui_log_item *);
+
+#endif	/* __XFS_BMAP_ITEM_H__ */