[RFC v6 PATCH 03/10] xfs: extra runtime reservation overhead for relog transactions

Brian Foster
2020-04-06T12:36:40Z

Every transaction reservation includes runtime overhead on top of
the reservation calculated in the struct xfs_trans_res. This
overhead is required for things like the CIL context ticket, log
headers, etc., that are stolen from individual transactions. Since
reservation for the relog transaction is entirely contributed by
regular transactions, this runtime reservation overhead must be
contributed as well. This means that a transaction that relogs one
or more items must include overhead for the current transaction as
well as for the relog transaction.

Define a new transaction flag to indicate that a transaction is
relog enabled. Plumb this state down to the log ticket allocation
and use it to bump the worst case overhead included in the
transaction. The overhead will eventually be transferred to the
relog system as needed for individual log items.

Signed-off-by: Brian Foster <bfoster@redhat.com>
---
fs/xfs/libxfs/xfs_shared.h | 1 +
fs/xfs/xfs_log.c | 12 +++++++++---
fs/xfs/xfs_log.h | 3 ++-
fs/xfs/xfs_log_cil.c | 2 +-
fs/xfs/xfs_log_priv.h | 1 +
fs/xfs/xfs_trans.c | 3 ++-
6 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_shared.h b/fs/xfs/libxfs/xfs_shared.h
index c45acbd3add9..1ede1e720a5c 100644
--- a/fs/xfs/libxfs/xfs_shared.h
+++ b/fs/xfs/libxfs/xfs_shared.h
@@ -65,6 +65,7 @@ void xfs_log_get_max_trans_res(struct xfs_mount *mp,
#define XFS_TRANS_DQ_DIRTY 0x10 /* at least one dquot in trx dirty */
#define XFS_TRANS_RESERVE 0x20 /* OK to use reserved data blocks */
#define XFS_TRANS_NO_WRITECOUNT 0x40 /* do not elevate SB writecount */
+#define XFS_TRANS_RELOG 0x80 /* requires extra relog overhead */
/*
* LOWMODE is used by the allocator to activate the lowspace algorithm - when
* free space is running low the extent allocator may choose to allocate an
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index d6b63490a78b..b55abde6c142 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -418,7 +418,8 @@ xfs_log_reserve(
int cnt,
struct xlog_ticket **ticp,
uint8_t client,
- bool permanent)
+ bool permanent,
+ bool relog)
{
struct xlog *log = mp->m_log;
struct xlog_ticket *tic;
@@ -433,7 +434,8 @@ xfs_log_reserve(
XFS_STATS_INC(mp, xs_try_logspace);

ASSERT(*ticp == NULL);
- tic = xlog_ticket_alloc(log, unit_bytes, cnt, client, permanent, 0);
+ tic = xlog_ticket_alloc(log, unit_bytes, cnt, client, permanent, relog,
+ 0);
*ticp = tic;

xlog_grant_push_ail(log, tic->t_cnt ? tic->t_unit_res * tic->t_cnt
@@ -831,7 +833,7 @@ xlog_unmount_write(
uint flags = XLOG_UNMOUNT_TRANS;
int error;

- error = xfs_log_reserve(mp, 600, 1, &tic, XFS_LOG, 0);
+ error = xfs_log_reserve(mp, 600, 1, &tic, XFS_LOG, false, false);
if (error)
goto out_err;

@@ -3421,6 +3423,7 @@ xlog_ticket_alloc(
int cnt,
char client,
bool permanent,
+ bool relog,
xfs_km_flags_t alloc_flags)
{
struct xlog_ticket *tic;
@@ -3431,6 +3434,9 @@ xlog_ticket_alloc(
return NULL;

unit_res = xfs_log_calc_unit_res(log->l_mp, unit_bytes);
+ /* double the overhead for the relog transaction */
+ if (relog)
+ unit_res += (unit_res - unit_bytes);

atomic_set(&tic->t_ref, 1);
tic->t_task = current;
diff --git a/fs/xfs/xfs_log.h b/fs/xfs/xfs_log.h
index 6d2f30f42245..f1089a4b299c 100644
--- a/fs/xfs/xfs_log.h
+++ b/fs/xfs/xfs_log.h
@@ -123,7 +123,8 @@ int xfs_log_reserve(struct xfs_mount *mp,
int count,
struct xlog_ticket **ticket,
uint8_t clientid,
- bool permanent);
+ bool permanent,
+ bool relog);
int xfs_log_regrant(struct xfs_mount *mp, struct xlog_ticket *tic);
void xfs_log_ungrant_bytes(struct xfs_mount *mp, int bytes);
void xfs_log_unmount(struct xfs_mount *mp);
diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
index b43f0e8f43f2..1c48e95402aa 100644
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c
@@ -37,7 +37,7 @@ xlog_cil_ticket_alloc(
{
struct xlog_ticket *tic;

- tic = xlog_ticket_alloc(log, 0, 1, XFS_TRANSACTION, 0,
+ tic = xlog_ticket_alloc(log, 0, 1, XFS_TRANSACTION, false, false,
KM_NOFS);

/*
diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index ec22c7a3867f..08d8ff9bce1a 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -465,6 +465,7 @@ xlog_ticket_alloc(
int count,
char client,
bool permanent,
+ bool relog,
xfs_km_flags_t alloc_flags);

diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index 4fbe11485bbb..1b25980315bd 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -177,6 +177,7 @@ xfs_trans_reserve(
*/
if (resp->tr_logres > 0) {
bool permanent = false;
+ bool relog = (tp->t_flags & XFS_TRANS_RELOG);

ASSERT(tp->t_log_res == 0 ||
tp->t_log_res == resp->tr_logres);
@@ -199,7 +200,7 @@ xfs_trans_reserve(
resp->tr_logres,
resp->tr_logcount,
&tp->t_ticket, XFS_TRANSACTION,
- permanent);
+ permanent, relog);
}

if (error)
--
2.21.1