@@ -983,6 +983,9 @@ xfs_log_item_init(
item->li_type = type;
item->li_ops = ops;
item->li_lv = NULL;
+#ifdef DEBUG
+ atomic64_set(&item->li_relog_res, 0);
+#endif
INIT_LIST_HEAD(&item->li_ail);
INIT_LIST_HEAD(&item->li_cil);
@@ -20,6 +20,7 @@
#include "xfs_trace.h"
#include "xfs_error.h"
#include "xfs_defer.h"
+#include "xfs_log_priv.h"
kmem_zone_t *xfs_trans_zone;
@@ -657,9 +658,19 @@ xfs_trans_relog_item(
struct xfs_trans *tp,
struct xfs_log_item *lip)
{
+ int nbytes;
+
+ ASSERT(tp->t_flags & XFS_TRANS_RELOG);
+
if (test_and_set_bit(XFS_LI_RELOG, &lip->li_flags))
return;
trace_xfs_relog_item(lip);
+
+ nbytes = xfs_relog_calc_res(lip);
+
+ tp->t_ticket->t_curr_res -= nbytes;
+ xfs_relog_res_account(lip, nbytes);
+ tp->t_flags |= XFS_TRANS_DIRTY;
}
void
@@ -667,9 +678,18 @@ xfs_trans_relog_item_cancel(
struct xfs_trans *tp,
struct xfs_log_item *lip)
{
+ int res;
+
if (!test_and_clear_bit(XFS_LI_RELOG, &lip->li_flags))
return;
trace_xfs_relog_item_cancel(lip);
+
+ res = xfs_relog_calc_res(lip);
+ if (tp)
+ tp->t_ticket->t_curr_res += res;
+ else
+ xfs_log_ungrant_bytes(lip->li_mountp, res);
+ xfs_relog_res_account(lip, -res);
}
/* Detach and unlock all of the items in a transaction */
@@ -48,6 +48,9 @@ struct xfs_log_item {
struct xfs_log_vec *li_lv; /* active log vector */
struct xfs_log_vec *li_lv_shadow; /* standby vector */
xfs_lsn_t li_seq; /* CIL commit seq */
+#ifdef DEBUG
+ atomic64_t li_relog_res; /* automatic relog log res */
+#endif
};
/*
@@ -216,6 +219,34 @@ xfs_trans_read_buf(
flags, bpp, ops);
}
+/*
+ * Calculate the log reservation required to enable relogging of a log item.
+ */
+static inline int
+xfs_relog_calc_res(
+ struct xfs_log_item *lip)
+{
+ int niovecs = 0;
+ int nbytes = 0;
+
+ /*
+ * The reservation consumed by a transaction at commit time consists of
+ * the total size of the formatted log vectors of the items dirtied by
+ * the transaction, an op header for each iovec in the log vectors, the
+ * unit reservation of the CIL context ticket, and extra iclog and op
+ * headers if the CIL context spans multiple iclogs (i.e. split
+ * reservation). The CIL ticket and split reservation are included by
+ * xfs_log_calc_unit_res().
+ */
+ lip->li_ops->iop_size(lip, &niovecs, &nbytes);
+ ASSERT(niovecs == 1);
+
+ nbytes += niovecs * sizeof(xlog_op_header_t);
+ nbytes = xfs_log_calc_unit_res(lip->li_mountp, nbytes);
+
+ return nbytes;
+}
+
struct xfs_buf *xfs_trans_getsb(xfs_trans_t *, struct xfs_mount *);
void xfs_trans_brelse(xfs_trans_t *, struct xfs_buf *);
@@ -894,6 +894,7 @@ xfs_trans_ail_init(
spin_lock_init(&ailp->ail_lock);
INIT_LIST_HEAD(&ailp->ail_buf_list);
init_waitqueue_head(&ailp->ail_empty);
+ atomic64_set(&ailp->ail_relog_res, 0);
ailp->ail_task = kthread_run(xfsaild, ailp, "xfsaild/%s",
ailp->ail_mount->m_super->s_id);
@@ -914,6 +915,7 @@ xfs_trans_ail_destroy(
{
struct xfs_ail *ailp = mp->m_ail;
+ ASSERT(atomic64_read(&ailp->ail_relog_res) == 0);
kthread_stop(ailp->ail_task);
kmem_free(ailp);
}
@@ -63,6 +63,7 @@ struct xfs_ail {
int ail_log_flush;
struct list_head ail_buf_list;
wait_queue_head_t ail_empty;
+ atomic64_t ail_relog_res;
};
/*
@@ -169,4 +170,17 @@ xfs_set_li_failed(
}
}
+static inline int64_t
+xfs_relog_res_account(
+ struct xfs_log_item *lip,
+ int64_t bytes)
+{
+#ifdef DEBUG
+ int64_t res;
+
+ res = atomic64_add_return(bytes, &lip->li_relog_res);
+ ASSERT(res == bytes || (bytes < 0 && res == 0));
+#endif
+ return atomic64_add_return(bytes, &lip->li_ailp->ail_relog_res);
+}
#endif /* __XFS_TRANS_PRIV_H__ */
The transaction that eventually commits relog enabled log items requires log reservation like any other transaction. It is not safe to acquire reservation on-demand because relogged items aren't processed until they are likely at the tail of the log and require movement in order to free up space in the log. As such, a relog transaction that blocks on log reservation is a likely deadlock vector. To address this problem, implement a model where relog reservation is contributed by the transaction that enables relogging on a particular item. Update the relog helper to transfer reservation from the transaction to the relog pool. The relog pool holds outstanding reservation such that it can be used to commit the item in an otherwise empty transaction. The upcoming relog mechanism is responsible to replenish the relog reservation as items are relogged. When relog is cancelled on a log item, transfer the outstanding relog reservation to the current transaction (if provided) for eventual release or otherwise release it directly to the grant heads. Note that this approach has several caveats: - Log reservation calculations for transactions that relog items must be increased accordingly. - The currently per-transaction overhead reservation (i.e. for things like the CIL ticket) must be included for each reloggable item because said items can be relogged in arbitrary combinations. - Relog reservation must be based on the worst case requirement for a log item. This is not a concern for fixed size log items, such as most intents. Items with more granular logging capability, such as buffers, can have additional ranges dirtied after relogging has been enabled and the relog subsystem must have enough reservation to accommodate. Signed-off-by: Brian Foster <bfoster@redhat.com> --- fs/xfs/xfs_log.c | 3 +++ fs/xfs/xfs_trans.c | 20 ++++++++++++++++++++ fs/xfs/xfs_trans.h | 31 +++++++++++++++++++++++++++++++ fs/xfs/xfs_trans_ail.c | 2 ++ fs/xfs/xfs_trans_priv.h | 14 ++++++++++++++ 5 files changed, 70 insertions(+)