xfs: move the repair extent list into its own file

Move the xrep_extent_list code into a separate file.  Logically, this
data structure is really just a clumsy bitmap, and in the next patch
we'll make this more obvious.  No functional changes.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>

fs/xfs/Makefile

@@ -158,6 +158,7 @@ xfs-$(CONFIG_XFS_QUOTA)		+= scrub/quota.o
 ifeq ($(CONFIG_XFS_ONLINE_REPAIR),y)
 xfs-y				+= $(addprefix scrub/, \
 				   agheader_repair.o \
+				   bitmap.o \
 				   repair.o \
 				   )
 endif

fs/xfs/scrub/bitmap.c

@@ -0,0 +1,208 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2018 Oracle.  All Rights Reserved.
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ */
+#include "xfs.h"
+#include "xfs_fs.h"
+#include "xfs_shared.h"
+#include "xfs_format.h"
+#include "xfs_trans_resv.h"
+#include "xfs_mount.h"
+#include "scrub/xfs_scrub.h"
+#include "scrub/scrub.h"
+#include "scrub/common.h"
+#include "scrub/trace.h"
+#include "scrub/repair.h"
+#include "scrub/bitmap.h"
+
+/* Collect a dead btree extent for later disposal. */
+int
+xrep_collect_btree_extent(
+	struct xfs_scrub	*sc,
+	struct xrep_extent_list	*exlist,
+	xfs_fsblock_t		fsbno,
+	xfs_extlen_t		len)
+{
+	struct xrep_extent	*rex;
+
+	trace_xrep_collect_btree_extent(sc->mp,
+			XFS_FSB_TO_AGNO(sc->mp, fsbno),
+			XFS_FSB_TO_AGBNO(sc->mp, fsbno), len);
+
+	rex = kmem_alloc(sizeof(struct xrep_extent), KM_MAYFAIL);
+	if (!rex)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&rex->list);
+	rex->fsbno = fsbno;
+	rex->len = len;
+	list_add_tail(&rex->list, &exlist->list);
+
+	return 0;
+}
+
+/*
+ * An error happened during the rebuild so the transaction will be cancelled.
+ * The fs will shut down, and the administrator has to unmount and run repair.
+ * Therefore, free all the memory associated with the list so we can die.
+ */
+void
+xrep_cancel_btree_extents(
+	struct xfs_scrub	*sc,
+	struct xrep_extent_list	*exlist)
+{
+	struct xrep_extent	*rex;
+	struct xrep_extent	*n;
+
+	for_each_xrep_extent_safe(rex, n, exlist) {
+		list_del(&rex->list);
+		kmem_free(rex);
+	}
+}
+
+/* Compare two btree extents. */
+static int
+xrep_btree_extent_cmp(
+	void			*priv,
+	struct list_head	*a,
+	struct list_head	*b)
+{
+	struct xrep_extent	*ap;
+	struct xrep_extent	*bp;
+
+	ap = container_of(a, struct xrep_extent, list);
+	bp = container_of(b, struct xrep_extent, list);
+
+	if (ap->fsbno > bp->fsbno)
+		return 1;
+	if (ap->fsbno < bp->fsbno)
+		return -1;
+	return 0;
+}
+
+/*
+ * Remove all the blocks mentioned in @sublist from the extents in @exlist.
+ *
+ * The intent is that callers will iterate the rmapbt for all of its records
+ * for a given owner to generate @exlist; and iterate all the blocks of the
+ * metadata structures that are not being rebuilt and have the same rmapbt
+ * owner to generate @sublist.  This routine subtracts all the extents
+ * mentioned in sublist from all the extents linked in @exlist, which leaves
+ * @exlist as the list of blocks that are not accounted for, which we assume
+ * are the dead blocks of the old metadata structure.  The blocks mentioned in
+ * @exlist can be reaped.
+ */
+#define LEFT_ALIGNED	(1 << 0)
+#define RIGHT_ALIGNED	(1 << 1)
+int
+xrep_subtract_extents(
+	struct xfs_scrub	*sc,
+	struct xrep_extent_list	*exlist,
+	struct xrep_extent_list	*sublist)
+{
+	struct list_head	*lp;
+	struct xrep_extent	*ex;
+	struct xrep_extent	*newex;
+	struct xrep_extent	*subex;
+	xfs_fsblock_t		sub_fsb;
+	xfs_extlen_t		sub_len;
+	int			state;
+	int			error = 0;
+
+	if (list_empty(&exlist->list) || list_empty(&sublist->list))
+		return 0;
+	ASSERT(!list_empty(&sublist->list));
+
+	list_sort(NULL, &exlist->list, xrep_btree_extent_cmp);
+	list_sort(NULL, &sublist->list, xrep_btree_extent_cmp);
+
+	/*
+	 * Now that we've sorted both lists, we iterate exlist once, rolling
+	 * forward through sublist and/or exlist as necessary until we find an
+	 * overlap or reach the end of either list.  We do not reset lp to the
+	 * head of exlist nor do we reset subex to the head of sublist.  The
+	 * list traversal is similar to merge sort, but we're deleting
+	 * instead.  In this manner we avoid O(n^2) operations.
+	 */
+	subex = list_first_entry(&sublist->list, struct xrep_extent,
+			list);
+	lp = exlist->list.next;
+	while (lp != &exlist->list) {
+		ex = list_entry(lp, struct xrep_extent, list);
+
+		/*
+		 * Advance subex and/or ex until we find a pair that
+		 * intersect or we run out of extents.
+		 */
+		while (subex->fsbno + subex->len <= ex->fsbno) {
+			if (list_is_last(&subex->list, &sublist->list))
+				goto out;
+			subex = list_next_entry(subex, list);
+		}
+		if (subex->fsbno >= ex->fsbno + ex->len) {
+			lp = lp->next;
+			continue;
+		}
+
+		/* trim subex to fit the extent we have */
+		sub_fsb = subex->fsbno;
+		sub_len = subex->len;
+		if (subex->fsbno < ex->fsbno) {
+			sub_len -= ex->fsbno - subex->fsbno;
+			sub_fsb = ex->fsbno;
+		}
+		if (sub_len > ex->len)
+			sub_len = ex->len;
+
+		state = 0;
+		if (sub_fsb == ex->fsbno)
+			state |= LEFT_ALIGNED;
+		if (sub_fsb + sub_len == ex->fsbno + ex->len)
+			state |= RIGHT_ALIGNED;
+		switch (state) {
+		case LEFT_ALIGNED:
+			/* Coincides with only the left. */
+			ex->fsbno += sub_len;
+			ex->len -= sub_len;
+			break;
+		case RIGHT_ALIGNED:
+			/* Coincides with only the right. */
+			ex->len -= sub_len;
+			lp = lp->next;
+			break;
+		case LEFT_ALIGNED | RIGHT_ALIGNED:
+			/* Total overlap, just delete ex. */
+			lp = lp->next;
+			list_del(&ex->list);
+			kmem_free(ex);
+			break;
+		case 0:
+			/*
+			 * Deleting from the middle: add the new right extent
+			 * and then shrink the left extent.
+			 */
+			newex = kmem_alloc(sizeof(struct xrep_extent),
+					KM_MAYFAIL);
+			if (!newex) {
+				error = -ENOMEM;
+				goto out;
+			}
+			INIT_LIST_HEAD(&newex->list);
+			newex->fsbno = sub_fsb + sub_len;
+			newex->len = ex->fsbno + ex->len - newex->fsbno;
+			list_add(&newex->list, &ex->list);
+			ex->len = sub_fsb - ex->fsbno;
+			lp = lp->next;
+			break;
+		default:
+			ASSERT(0);
+			break;
+		}
+	}
+
+out:
+	return error;
+}
+#undef LEFT_ALIGNED
+#undef RIGHT_ALIGNED

fs/xfs/scrub/bitmap.h

@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2018 Oracle.  All Rights Reserved.
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ */
+#ifndef __XFS_SCRUB_BITMAP_H__
+#define __XFS_SCRUB_BITMAP_H__
+
+struct xrep_extent {
+	struct list_head	list;
+	xfs_fsblock_t		fsbno;
+	xfs_extlen_t		len;
+};
+
+struct xrep_extent_list {
+	struct list_head	list;
+};
+
+static inline void
+xrep_init_extent_list(
+	struct xrep_extent_list		*exlist)
+{
+	INIT_LIST_HEAD(&exlist->list);
+}
+
+#define for_each_xrep_extent_safe(rbe, n, exlist) \
+	list_for_each_entry_safe((rbe), (n), &(exlist)->list, list)
+int xrep_collect_btree_extent(struct xfs_scrub *sc,
+		struct xrep_extent_list *btlist, xfs_fsblock_t fsbno,
+		xfs_extlen_t len);
+void xrep_cancel_btree_extents(struct xfs_scrub *sc,
+		struct xrep_extent_list *btlist);
+int xrep_subtract_extents(struct xfs_scrub *sc,
+		struct xrep_extent_list *exlist,
+		struct xrep_extent_list *sublist);
+
+#endif	/* __XFS_SCRUB_BITMAP_H__ */