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diff --git a/fs/xfs/scrub/health.c b/fs/xfs/scrub/health.c
new file mode 100644
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+++ b/fs/xfs/scrub/health.c
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+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2019 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 "xfs_defer.h"
+#include "xfs_btree.h"
+#include "xfs_bit.h"
+#include "xfs_log_format.h"
+#include "xfs_trans.h"
+#include "xfs_sb.h"
+#include "xfs_inode.h"
+#include "xfs_health.h"
+#include "scrub/scrub.h"
+#include "scrub/health.h"
+
+/*
+ * Scrub and In-Core Filesystem Health Assessments
+ * ===============================================
+ *
+ * Online scrub and repair have the time and the ability to perform stronger
+ * checks than we can do from the metadata verifiers, because they can
+ * cross-reference records between data structures.  Therefore, scrub is in a
+ * good position to update the online filesystem health assessments to reflect
+ * the good/bad state of the data structure.
+ *
+ * We therefore extend scrub in the following ways to achieve this:
+ *
+ * 1. Create a "sick_mask" field in the scrub context.  When we're setting up a
+ * scrub call, set this to the default XFS_SICK_* flag(s) for the selected
+ * scrub type (call it A).  Scrub and repair functions can override the default
+ * sick_mask value if they choose.
+ *
+ * 2. If the scrubber returns a runtime error code, we exit making no changes
+ * to the incore sick state.
+ *
+ * 3. If the scrubber finds that A is clean, use sick_mask to clear the incore
+ * sick flags before exiting.
+ *
+ * 4. If the scrubber finds that A is corrupt, use sick_mask to set the incore
+ * sick flags.  If the user didn't want to repair then we exit, leaving the
+ * metadata structure unfixed and the sick flag set.
+ *
+ * 5. Now we know that A is corrupt and the user wants to repair, so run the
+ * repairer.  If the repairer returns an error code, we exit with that error
+ * code, having made no further changes to the incore sick state.
+ *
+ * 6. If repair rebuilds A correctly and the subsequent re-scrub of A is clean,
+ * use sick_mask to clear the incore sick flags.  This should have the effect
+ * that A is no longer marked sick.
+ *
+ * 7. If repair rebuilds A incorrectly, the re-scrub will find it corrupt and
+ * use sick_mask to set the incore sick flags.  This should have no externally
+ * visible effect since we already set them in step (4).
+ *
+ * There are some complications to this story, however.  For certain types of
+ * complementary metadata indices (e.g. inobt/finobt), it is easier to rebuild
+ * both structures at the same time.  The following principles apply to this
+ * type of repair strategy:
+ *
+ * 8. Any repair function that rebuilds multiple structures should update
+ * sick_mask_visible to reflect whatever other structures are rebuilt, and
+ * verify that all the rebuilt structures can pass a scrub check.  The outcomes
+ * of 5-7 still apply, but with a sick_mask that covers everything being
+ * rebuilt.
+ */
+
+/* Map our scrub type to a sick mask and a set of health update functions. */
+
+enum xchk_health_group {
+	XHG_FS = 1,
+	XHG_RT,
+	XHG_AG,
+	XHG_INO,
+};
+
+struct xchk_health_map {
+	enum xchk_health_group	group;
+	unsigned int		sick_mask;
+};
+
+static const struct xchk_health_map type_to_health_flag[XFS_SCRUB_TYPE_NR] = {
+	[XFS_SCRUB_TYPE_SB]		= { XHG_AG,  XFS_SICK_AG_SB },
+	[XFS_SCRUB_TYPE_AGF]		= { XHG_AG,  XFS_SICK_AG_AGF },
+	[XFS_SCRUB_TYPE_AGFL]		= { XHG_AG,  XFS_SICK_AG_AGFL },
+	[XFS_SCRUB_TYPE_AGI]		= { XHG_AG,  XFS_SICK_AG_AGI },
+	[XFS_SCRUB_TYPE_BNOBT]		= { XHG_AG,  XFS_SICK_AG_BNOBT },
+	[XFS_SCRUB_TYPE_CNTBT]		= { XHG_AG,  XFS_SICK_AG_CNTBT },
+	[XFS_SCRUB_TYPE_INOBT]		= { XHG_AG,  XFS_SICK_AG_INOBT },
+	[XFS_SCRUB_TYPE_FINOBT]		= { XHG_AG,  XFS_SICK_AG_FINOBT },
+	[XFS_SCRUB_TYPE_RMAPBT]		= { XHG_AG,  XFS_SICK_AG_RMAPBT },
+	[XFS_SCRUB_TYPE_REFCNTBT]	= { XHG_AG,  XFS_SICK_AG_REFCNTBT },
+	[XFS_SCRUB_TYPE_INODE]		= { XHG_INO, XFS_SICK_INO_CORE },
+	[XFS_SCRUB_TYPE_BMBTD]		= { XHG_INO, XFS_SICK_INO_BMBTD },
+	[XFS_SCRUB_TYPE_BMBTA]		= { XHG_INO, XFS_SICK_INO_BMBTA },
+	[XFS_SCRUB_TYPE_BMBTC]		= { XHG_INO, XFS_SICK_INO_BMBTC },
+	[XFS_SCRUB_TYPE_DIR]		= { XHG_INO, XFS_SICK_INO_DIR },
+	[XFS_SCRUB_TYPE_XATTR]		= { XHG_INO, XFS_SICK_INO_XATTR },
+	[XFS_SCRUB_TYPE_SYMLINK]	= { XHG_INO, XFS_SICK_INO_SYMLINK },
+	[XFS_SCRUB_TYPE_PARENT]		= { XHG_INO, XFS_SICK_INO_PARENT },
+	[XFS_SCRUB_TYPE_RTBITMAP]	= { XHG_RT,  XFS_SICK_RT_BITMAP },
+	[XFS_SCRUB_TYPE_RTSUM]		= { XHG_RT,  XFS_SICK_RT_SUMMARY },
+	[XFS_SCRUB_TYPE_UQUOTA]		= { XHG_FS,  XFS_SICK_FS_UQUOTA },
+	[XFS_SCRUB_TYPE_GQUOTA]		= { XHG_FS,  XFS_SICK_FS_GQUOTA },
+	[XFS_SCRUB_TYPE_PQUOTA]		= { XHG_FS,  XFS_SICK_FS_PQUOTA },
+	[XFS_SCRUB_TYPE_FSCOUNTERS]	= { XHG_FS,  XFS_SICK_FS_COUNTERS },
+};
+
+/* Return the health status mask for this scrub type. */
+unsigned int
+xchk_health_mask_for_scrub_type(
+	__u32			scrub_type)
+{
+	return type_to_health_flag[scrub_type].sick_mask;
+}
+
+/*
+ * Update filesystem health assessments based on what we found and did.
+ *
+ * If the scrubber finds errors, we mark sick whatever's mentioned in
+ * sick_mask, no matter whether this is a first scan or an
+ * evaluation of repair effectiveness.
+ *
+ * Otherwise, no direct corruption was found, so mark whatever's in
+ * sick_mask as healthy.
+ */
+void
+xchk_update_health(
+	struct xfs_scrub	*sc)
+{
+	struct xfs_perag	*pag;
+	bool			bad;
+
+	if (!sc->sick_mask)
+		return;
+
+	bad = (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT);
+	switch (type_to_health_flag[sc->sm->sm_type].group) {
+	case XHG_AG:
+		pag = xfs_perag_get(sc->mp, sc->sm->sm_agno);
+		if (bad)
+			xfs_ag_mark_sick(pag, sc->sick_mask);
+		else
+			xfs_ag_mark_healthy(pag, sc->sick_mask);
+		xfs_perag_put(pag);
+		break;
+	case XHG_INO:
+		if (!sc->ip)
+			return;
+		if (bad)
+			xfs_inode_mark_sick(sc->ip, sc->sick_mask);
+		else
+			xfs_inode_mark_healthy(sc->ip, sc->sick_mask);
+		break;
+	case XHG_FS:
+		if (bad)
+			xfs_fs_mark_sick(sc->mp, sc->sick_mask);
+		else
+			xfs_fs_mark_healthy(sc->mp, sc->sick_mask);
+		break;
+	case XHG_RT:
+		if (bad)
+			xfs_rt_mark_sick(sc->mp, sc->sick_mask);
+		else
+			xfs_rt_mark_healthy(sc->mp, sc->sick_mask);
+		break;
+	default:
+		ASSERT(0);
+		break;
+	}
+}
+
+/* Is the given per-AG btree healthy enough for scanning? */
+bool
+xchk_ag_btree_healthy_enough(
+	struct xfs_scrub	*sc,
+	struct xfs_perag	*pag,
+	xfs_btnum_t		btnum)
+{
+	unsigned int		mask = 0;
+
+	/*
+	 * We always want the cursor if it's the same type as whatever we're
+	 * scrubbing, even if we already know the structure is corrupt.
+	 *
+	 * Otherwise, we're only interested in the btree for cross-referencing.
+	 * If we know the btree is bad then don't bother, just set XFAIL.
+	 */
+	switch (btnum) {
+	case XFS_BTNUM_BNO:
+		if (sc->sm->sm_type == XFS_SCRUB_TYPE_BNOBT)
+			return true;
+		mask = XFS_SICK_AG_BNOBT;
+		break;
+	case XFS_BTNUM_CNT:
+		if (sc->sm->sm_type == XFS_SCRUB_TYPE_CNTBT)
+			return true;
+		mask = XFS_SICK_AG_CNTBT;
+		break;
+	case XFS_BTNUM_INO:
+		if (sc->sm->sm_type == XFS_SCRUB_TYPE_INOBT)
+			return true;
+		mask = XFS_SICK_AG_INOBT;
+		break;
+	case XFS_BTNUM_FINO:
+		if (sc->sm->sm_type == XFS_SCRUB_TYPE_FINOBT)
+			return true;
+		mask = XFS_SICK_AG_FINOBT;
+		break;
+	case XFS_BTNUM_RMAP:
+		if (sc->sm->sm_type == XFS_SCRUB_TYPE_RMAPBT)
+			return true;
+		mask = XFS_SICK_AG_RMAPBT;
+		break;
+	case XFS_BTNUM_REFC:
+		if (sc->sm->sm_type == XFS_SCRUB_TYPE_REFCNTBT)
+			return true;
+		mask = XFS_SICK_AG_REFCNTBT;
+		break;
+	default:
+		ASSERT(0);
+		return true;
+	}
+
+	if (xfs_ag_has_sickness(pag, mask)) {
+		sc->sm->sm_flags |= XFS_SCRUB_OFLAG_XFAIL;
+		return false;
+	}
+
+	return true;
+}