xfs: disable reaping in fscounters scrub

The fscounters scrub code doesn't work properly because it cannot
quiesce updates to the percpu counters in the filesystem, hence it
returns false corruption reports.  This has been fixed properly in
one of the online repair patchsets that are under review by replacing
the xchk_disable_reaping calls with an exclusive filesystem freeze.
Disabling background gc isn't sufficient to fix the problem.

In other words, scrub doesn't need to call xfs_inodegc_stop, which is
just as well since it wasn't correct to allow scrub to call
xfs_inodegc_start when something else could be calling xfs_inodegc_stop
(e.g. trying to freeze the filesystem).

Neuter the scrubber for now, and remove the xchk_*_reaping functions.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/scrub/common.c

@@ -1164,32 +1164,6 @@ xchk_metadata_inode_forks(
 	return 0;
 }
 
-/* Pause background reaping of resources. */
-void
-xchk_stop_reaping(
-	struct xfs_scrub	*sc)
-{
-	sc->flags |= XCHK_REAPING_DISABLED;
-	xfs_blockgc_stop(sc->mp);
-	xfs_inodegc_stop(sc->mp);
-}
-
-/* Restart background reaping of resources. */
-void
-xchk_start_reaping(
-	struct xfs_scrub	*sc)
-{
-	/*
-	 * Readonly filesystems do not perform inactivation or speculative
-	 * preallocation, so there's no need to restart the workers.
-	 */
-	if (!xfs_is_readonly(sc->mp)) {
-		xfs_inodegc_start(sc->mp);
-		xfs_blockgc_start(sc->mp);
-	}
-	sc->flags &= ~XCHK_REAPING_DISABLED;
-}
-
 /*
  * Enable filesystem hooks (i.e. runtime code patching) before starting a scrub
  * operation.  Callers must not hold any locks that intersect with the CPU

fs/xfs/scrub/common.h

@@ -156,8 +156,6 @@ static inline bool xchk_skip_xref(struct xfs_scrub_metadata *sm)
 }
 
 int xchk_metadata_inode_forks(struct xfs_scrub *sc);
-void xchk_stop_reaping(struct xfs_scrub *sc);
-void xchk_start_reaping(struct xfs_scrub *sc);
 
 /*
  * Setting up a hook to wait for intents to drain is costly -- we have to take

fs/xfs/scrub/fscounters.c

@@ -150,13 +150,6 @@ xchk_setup_fscounters(
 	if (error)
 		return error;
 
-	/*
-	 * Pause background reclaim while we're scrubbing to reduce the
-	 * likelihood of background perturbations to the counters throwing off
-	 * our calculations.
-	 */
-	xchk_stop_reaping(sc);
-
 	return xchk_trans_alloc(sc, 0);
 }
 
@@ -453,6 +446,12 @@ xchk_fscounters(
 	if (frextents > mp->m_sb.sb_rextents)
 		xchk_set_corrupt(sc);
 
+	/*
+	 * XXX: We can't quiesce percpu counter updates, so exit early.
+	 * This can be re-enabled when we gain exclusive freeze functionality.
+	 */
+	return 0;
+
 	/*
 	 * If ifree exceeds icount by more than the minimum variance then
 	 * something's probably wrong with the counters.

fs/xfs/scrub/scrub.c

@@ -186,8 +186,6 @@ xchk_teardown(
 	}
 	if (sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR)
 		mnt_drop_write_file(sc->file);
-	if (sc->flags & XCHK_REAPING_DISABLED)
-		xchk_start_reaping(sc);
 	if (sc->buf) {
 		if (sc->buf_cleanup)
 			sc->buf_cleanup(sc->buf);

fs/xfs/scrub/scrub.h

@@ -106,7 +106,6 @@ struct xfs_scrub {
 
 /* XCHK state flags grow up from zero, XREP state flags grown down from 2^31 */
 #define XCHK_TRY_HARDER		(1 << 0)  /* can't get resources, try again */
-#define XCHK_REAPING_DISABLED	(1 << 1)  /* background block reaping paused */
 #define XCHK_FSGATES_DRAIN	(1 << 2)  /* defer ops draining enabled */
 #define XCHK_NEED_DRAIN		(1 << 3)  /* scrub needs to drain defer ops */
 #define XREP_ALREADY_FIXED	(1 << 31) /* checking our repair work */

fs/xfs/scrub/trace.h

@@ -98,7 +98,6 @@ TRACE_DEFINE_ENUM(XFS_SCRUB_TYPE_FSCOUNTERS);
 
 #define XFS_SCRUB_STATE_STRINGS \
 	{ XCHK_TRY_HARDER,			"try_harder" }, \
-	{ XCHK_REAPING_DISABLED,		"reaping_disabled" }, \
 	{ XCHK_FSGATES_DRAIN,			"fsgates_drain" }, \
 	{ XCHK_NEED_DRAIN,			"need_drain" }, \
 	{ XREP_ALREADY_FIXED,			"already_fixed" }