From: Darrick J. Wong <djwong@xxxxxxxxxx>
Calculate the maximum number of CoW staging extents that can be reaped
in a single transaction chain. The rough calculation here is:
nr_extents = (logres - reservation used by any one step) /
(space used by intents per extent +
space used for a few buffer invalidations)
Signed-off-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
---
fs/xfs/scrub/trace.h | 1 +
fs/xfs/scrub/reap.c | 88 +++++++++++++++++++++++++++++++++++++++++++++++---
2 files changed, 84 insertions(+), 5 deletions(-)
diff --git a/fs/xfs/scrub/trace.h b/fs/xfs/scrub/trace.h
index d39da0e67024fb..a9da22f50534cb 100644
--- a/fs/xfs/scrub/trace.h
+++ b/fs/xfs/scrub/trace.h
@@ -2041,6 +2041,7 @@ DEFINE_EVENT(xrep_reap_limits_class, name, \
unsigned int max_deferred), \
TP_ARGS(tp, per_binval, max_binval, step_size, per_intent, max_deferred))
DEFINE_REPAIR_REAP_LIMITS_EVENT(xreap_agextent_limits);
+DEFINE_REPAIR_REAP_LIMITS_EVENT(xreap_agcow_limits);
DECLARE_EVENT_CLASS(xrep_reap_find_class,
TP_PROTO(const struct xfs_group *xg, xfs_agblock_t agbno,
diff --git a/fs/xfs/scrub/reap.c b/fs/xfs/scrub/reap.c
index 929ea3c453d313..aaef7e6771a045 100644
--- a/fs/xfs/scrub/reap.c
+++ b/fs/xfs/scrub/reap.c
@@ -443,7 +443,7 @@ xreap_agextent_iter(
if (rs->oinfo == &XFS_RMAP_OINFO_COW) {
/*
- * If we're unmapping CoW staging extents, remove the
+ * t0: Unmapping CoW staging extents, remove the
* records from the refcountbt, which will remove the
* rmap record as well.
*/
@@ -475,7 +475,7 @@ xreap_agextent_iter(
}
/*
- * If we're getting rid of CoW staging extents, use deferred work items
+ * t2: To get rid of CoW staging extents, use deferred work items
* to remove the refcountbt records (which removes the rmap records)
* and free the extent. We're not worried about the system going down
* here because log recovery walks the refcount btree to clean out the
@@ -626,6 +626,84 @@ xreap_configure_agextent_limits(
step_size, per_intent, rs->max_deferred);
}
+/*
+ * Compute the maximum number of intent items that reaping can attach to the
+ * scrub transaction given the worst case log overhead of the intent items
+ * needed to reap a single CoW staging extent. This is not for freeing
+ * metadata blocks.
+ */
+STATIC void
+xreap_configure_agcow_limits(
+ struct xreap_state *rs)
+{
+ struct xfs_scrub *sc = rs->sc;
+ struct xfs_mount *mp = sc->mp;
+
+ /*
+ * In the worst case, relogging an intent item causes both an intent
+ * item and a done item to be attached to a transaction for each extent
+ * that we'd like to process.
+ */
+ const unsigned int efi = xfs_efi_log_space(1) +
+ xfs_efd_log_space(1);
+ const unsigned int rui = xfs_rui_log_space(1) +
+ xfs_rud_log_space();
+ const unsigned int cui = xfs_cui_log_space(1) +
+ xfs_cud_log_space();
+
+ /*
+ * Various things can happen when reaping non-CoW metadata blocks:
+ *
+ * t0: Unmapping crosslinked CoW blocks: deferred removal of refcount
+ * record, which defers removal of rmap record
+ *
+ * t2: Freeing CoW blocks: deferred removal of refcount record, which
+ * defers removal of rmap record; and deferred removal of the space
+ *
+ * For simplicity, we'll use the worst-case intents size to determine
+ * the maximum number of deferred extents before we have to finish the
+ * whole chain. If we're trying to reap a btree larger than this size,
+ * a crash midway through reaping can result in leaked blocks.
+ */
+ const unsigned int t0 = cui + rui;
+ const unsigned int t2 = cui + rui + efi;
+ const unsigned int per_intent = max(t0, t2);
+
+ /*
+ * For each transaction in a reap chain, we must be able to take one
+ * step in the defer item chain, which should only consist of CUI, EFI,
+ * or RUI items.
+ */
+ const unsigned int f1 = xfs_calc_finish_efi_reservation(mp, 1);
+ const unsigned int f2 = xfs_calc_finish_rui_reservation(mp, 1);
+ const unsigned int f3 = xfs_calc_finish_cui_reservation(mp, 1);
+ const unsigned int step_size = max3(f1, f2, f3);
+
+ /* Largest buffer size (in fsblocks) that can be invalidated. */
+ const unsigned int max_binval = xrep_binval_max_fsblocks(mp);
+
+ /* Overhead of invalidating one buffer */
+ const unsigned int per_binval =
+ xfs_buf_inval_log_space(1, XFS_B_TO_FSBT(mp, max_binval));
+
+ /*
+ * For each transaction in a reap chain, we can delete some number of
+ * extents and invalidate some number of blocks. We assume that CoW
+ * staging extents are usually more than 1 fsblock, and that there
+ * shouldn't be any buffers for those blocks. From the assumptions,
+ * set the number of deferrals to use as much of the reservation as
+ * it can, but leave space to invalidate 1/8th that number of buffers.
+ */
+ const unsigned int variable_overhead = per_intent +
+ (per_binval / 8);
+
+ xreap_configure_limits(rs, step_size, variable_overhead, per_intent,
+ per_binval);
+
+ trace_xreap_agcow_limits(sc->tp, per_binval, rs->max_binval, step_size,
+ per_intent, rs->max_deferred);
+}
+
/*
* Break an AG metadata extent into sub-extents by fate (crosslinked, not
* crosslinked), and dispose of each sub-extent separately.
@@ -800,15 +878,15 @@ xrep_reap_fsblocks(
.sc = sc,
.oinfo = oinfo,
.resv = XFS_AG_RESV_NONE,
- .max_binval = XREAP_MAX_BINVAL,
- .max_deferred = XREAP_MAX_DEFER_CHAIN,
};
int error;
ASSERT(xfs_has_rmapbt(sc->mp));
ASSERT(sc->ip != NULL);
- if (oinfo != &XFS_RMAP_OINFO_COW)
+ if (oinfo == &XFS_RMAP_OINFO_COW)
+ xreap_configure_agcow_limits(&rs);
+ else
xreap_configure_agextent_limits(&rs);
error = xfsb_bitmap_walk(bitmap, xreap_fsmeta_extent, &rs);
if (error)
