[PATCH 01/11] xfs: don't try to write a start record into every iclog

Dave Chinner
2020-03-04T07:54:09Z

From: Dave Chinner <dchinner@redhat.com>

The xlog_write() function iterates over iclogs until it completes
writing all the log vectors passed in. The ticket tracks whether
a start record has been written or not, so only the first iclog gets
a start record. We only ever pass single use tickets to
xlog_write() we only ever need to write a start record once per
xlog_write() call.

Hence we don't need to store whether we should write a start record
in the ticket as the callers provide all the information we need to
determine if a start record should be written. For the moment, we
have to ensure that we clear the XLOG_TIC_INITED appropriately so
the code in xfs_log_done() still works correctly for committing
transactions.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
fs/xfs/xfs_log.c | 68 +++++++++++++++++++++++++-----------------------
1 file changed, 35 insertions(+), 33 deletions(-)

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index f6006d94a581..5b0568a86c07 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -2148,23 +2148,21 @@ xlog_print_trans(
}

/*
- * Calculate the potential space needed by the log vector. Each region gets
- * its own xlog_op_header_t and may need to be double word aligned.
+ * Calculate the potential space needed by the log vector. We may need a
+ * start record, and each region gets its own xlog_op_header_t and may need to
+ * be double word aligned.
*/
static int
xlog_write_calc_vec_length(
struct xlog_ticket *ticket,
- struct xfs_log_vec *log_vector)
+ struct xfs_log_vec *log_vector,
+ bool need_start_rec)
{
struct xfs_log_vec *lv;
- int headers = 0;
+ int headers = need_start_rec ? 1 : 0;
int len = 0;
int i;

- /* acct for start rec of xact */
- if (ticket->t_flags & XLOG_TIC_INITED)
- headers++;
-
for (lv = log_vector; lv; lv = lv->lv_next) {
/* we don't write ordered log vectors */
if (lv->lv_buf_len == XFS_LOG_VEC_ORDERED)
@@ -2186,27 +2184,16 @@ xlog_write_calc_vec_length(
return len;
}

-/*
- * If first write for transaction, insert start record We can't be trying to
- * commit if we are inited. We can't have any "partial_copy" if we are inited.
- */
-static int
+static void
xlog_write_start_rec(
struct xlog_op_header *ophdr,
struct xlog_ticket *ticket)
{
- if (!(ticket->t_flags & XLOG_TIC_INITED))
- return 0;
-
ophdr->oh_tid = cpu_to_be32(ticket->t_tid);
ophdr->oh_clientid = ticket->t_clientid;
ophdr->oh_len = 0;
ophdr->oh_flags = XLOG_START_TRANS;
ophdr->oh_res2 = 0;
-
- ticket->t_flags &= ~XLOG_TIC_INITED;
-
- return sizeof(struct xlog_op_header);
}

static xlog_op_header_t *
@@ -2404,25 +2391,29 @@ xlog_write(
int record_cnt = 0;
int data_cnt = 0;
int error = 0;
+ int start_rec_size = sizeof(struct xlog_op_header);

*start_lsn = 0;

- len = xlog_write_calc_vec_length(ticket, log_vector);

/*
* Region headers and bytes are already accounted for.
* We only need to take into account start records and
* split regions in this function.
*/
- if (ticket->t_flags & XLOG_TIC_INITED)
+ if (ticket->t_flags & XLOG_TIC_INITED) {
ticket->t_curr_res -= sizeof(xlog_op_header_t);
+ ticket->t_flags &= ~XLOG_TIC_INITED;
+ }

/*
* Commit record headers need to be accounted for. These
* come in as separate writes so are easy to detect.
*/
- if (flags & (XLOG_COMMIT_TRANS | XLOG_UNMOUNT_TRANS))
+ if (flags & (XLOG_COMMIT_TRANS | XLOG_UNMOUNT_TRANS)) {
ticket->t_curr_res -= sizeof(xlog_op_header_t);
+ start_rec_size = 0;
+ }

if (ticket->t_curr_res < 0) {
xfs_alert_tag(log->l_mp, XFS_PTAG_LOGRES,
@@ -2431,6 +2422,8 @@ xlog_write(
xfs_force_shutdown(log->l_mp, SHUTDOWN_LOG_IO_ERROR);
}

+ len = xlog_write_calc_vec_length(ticket, log_vector, start_rec_size);
+
index = 0;
lv = log_vector;
vecp = lv->lv_iovecp;
@@ -2446,9 +2439,20 @@ xlog_write(
ASSERT(log_offset <= iclog->ic_size - 1);
ptr = iclog->ic_datap + log_offset;

- /* start_lsn is the first lsn written to. That's all we need. */
+ /*
+ * Before we start formatting log vectors, we need to write a
+ * start record and record the lsn of the iclog that we write
+ * the start record into. Only do this for the first iclog we
+ * write to.
+ */
if (!*start_lsn)
*start_lsn = be64_to_cpu(iclog->ic_header.h_lsn);
+ if (start_rec_size) {
+ xlog_write_start_rec(ptr, ticket);
+ xlog_write_adv_cnt(&ptr, &len, &log_offset,
+ start_rec_size);
+ record_cnt++;
+ }

/*
* This loop writes out as many regions as can fit in the amount
@@ -2457,7 +2461,6 @@ xlog_write(
while (lv && (!lv->lv_niovecs || index < lv->lv_niovecs)) {
struct xfs_log_iovec *reg;
struct xlog_op_header *ophdr;
- int start_rec_copy;
int copy_len;
int copy_off;
bool ordered = false;
@@ -2473,13 +2476,6 @@ xlog_write(
ASSERT(reg->i_len % sizeof(int32_t) == 0);
ASSERT((unsigned long)ptr % sizeof(int32_t) == 0);

- start_rec_copy = xlog_write_start_rec(ptr, ticket);
- if (start_rec_copy) {
- record_cnt++;
- xlog_write_adv_cnt(&ptr, &len, &log_offset,
- start_rec_copy);
- }
-
ophdr = xlog_write_setup_ophdr(log, ptr, ticket, flags);
if (!ophdr)
return -EIO;
@@ -2509,10 +2505,15 @@ xlog_write(
xlog_write_adv_cnt(&ptr, &len, &log_offset,
copy_len);
}
- copy_len += start_rec_copy + sizeof(xlog_op_header_t);
+ copy_len += sizeof(xlog_op_header_t);
record_cnt++;
data_cnt += contwr ? copy_len : 0;

+ if (start_rec_size) {
+ copy_len += start_rec_size;
+ start_rec_size = 0;
+ }
+
error = xlog_write_copy_finish(log, iclog, flags,
&record_cnt, &data_cnt,
&partial_copy,
@@ -2550,6 +2551,7 @@ xlog_write(
break;
}
}
+ start_rec_size = 0;
}

ASSERT(len == 0);
--
2.24.0.rc0