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authorDarrick J. Wong <darrick.wong@oracle.com>2020-09-27 16:18:13 -0700
committerDarrick J. Wong <darrick.wong@oracle.com>2020-10-07 08:40:28 -0700
commit4e919af7827a6adfc28e82cd6c4ffcfcc3dd6118 (patch)
tree289d32e2f0a16fdf8838bf33557ec91650b5359c /fs/xfs/xfs_trans.h
parent27dada070d59c28a441f1907d2cec891b17dcb26 (diff)
xfs: periodically relog deferred intent items
There's a subtle design flaw in the deferred log item code that can lead to pinning the log tail. Taking up the defer ops chain examples from the previous commit, we can get trapped in sequences like this: Caller hands us a transaction t0 with D0-D3 attached. The defer ops chain will look like the following if the transaction rolls succeed: t1: D0(t0), D1(t0), D2(t0), D3(t0) t2: d4(t1), d5(t1), D1(t0), D2(t0), D3(t0) t3: d5(t1), D1(t0), D2(t0), D3(t0) ... t9: d9(t7), D3(t0) t10: D3(t0) t11: d10(t10), d11(t10) t12: d11(t10) In transaction 9, we finish d9 and try to roll to t10 while holding onto an intent item for D3 that we logged in t0. The previous commit changed the order in which we place new defer ops in the defer ops processing chain to reduce the maximum chain length. Now make xfs_defer_finish_noroll capable of relogging the entire chain periodically so that we can always move the log tail forward. Most chains will never get relogged, except for operations that generate very long chains (large extents containing many blocks with different sharing levels) or are on filesystems with small logs and a lot of ongoing metadata updates. Callers are now required to ensure that the transaction reservation is large enough to handle logging done items and new intent items for the maximum possible chain length. Most callers are careful to keep the chain lengths low, so the overhead should be minimal. The decision to relog an intent item is made based on whether the intent was logged in a previous checkpoint, since there's no point in relogging an intent into the same checkpoint. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Brian Foster <bfoster@redhat.com>
Diffstat (limited to 'fs/xfs/xfs_trans.h')
-rw-r--r--fs/xfs/xfs_trans.h10
1 files changed, 10 insertions, 0 deletions
diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
index 186e77d08cc1..084658946cc8 100644
--- a/fs/xfs/xfs_trans.h
+++ b/fs/xfs/xfs_trans.h
@@ -75,6 +75,8 @@ struct xfs_item_ops {
int (*iop_recover)(struct xfs_log_item *lip,
struct list_head *capture_list);
bool (*iop_match)(struct xfs_log_item *item, uint64_t id);
+ struct xfs_log_item *(*iop_relog)(struct xfs_log_item *intent,
+ struct xfs_trans *tp);
};
/* Is this log item a deferred action intent? */
@@ -258,4 +260,12 @@ void xfs_trans_buf_copy_type(struct xfs_buf *dst_bp,
extern kmem_zone_t *xfs_trans_zone;
+static inline struct xfs_log_item *
+xfs_trans_item_relog(
+ struct xfs_log_item *lip,
+ struct xfs_trans *tp)
+{
+ return lip->li_ops->iop_relog(lip, tp);
+}
+
#endif /* __XFS_TRANS_H__ */