[04/16] xfs: embed the xlog_op_header in the commit record

Commit Message

Dave Chinner Nov. 9, 2021, 1:50 a.m. UTC

Remove the final case where xlog_write() has to prepend an opheader
to a log transaction. Similar to the start record, the commit record
is just an empty opheader with a XLOG_COMMIT_TRANS type, so we can
just make this the payload for the region being passed to
xlog_write() and remove the special handling in xlog_write() for
the commit record.

Signed-off-by: Dave Chinner <[e-mail]>
Reviewed-by: Darrick J. Wong <[e-mail]>
---
 fs/xfs/xfs_log.c     | 22 ++++++----------------
 fs/xfs/xfs_log_cil.c | 11 +++++++++--
 2 files changed, 15 insertions(+), 18 deletions(-)

Comments

Christoph Hellwig Nov. 11, 2021, 8 a.m. UTC | #1

On Tue, Nov 09, 2021 at 12:50:43PM +1100, Dave Chinner wrote:
> -			if (optype & XLOG_START_TRANS) {
> +			if (optype) {

Shouldn't this explicitly check for XLOG_START_TRANS or
XLOG_UNMOUNT_TRANS?  The cont flags can't really happen here, so it
won't make a functional difference, but it would document the intent
much better.

Otherwise looks good:

Reviewed-by: Christoph Hellwig <[e-mail]>

Dave Chinner Nov. 18, 2021, 4:43 a.m. UTC | #2

On Thu, Nov 11, 2021 at 12:00:04AM -0800, Christoph Hellwig wrote:
> On Tue, Nov 09, 2021 at 12:50:43PM +1100, Dave Chinner wrote:
> > -			if (optype & XLOG_START_TRANS) {
> > +			if (optype) {
> 
> Shouldn't this explicitly check for XLOG_START_TRANS or
> XLOG_UNMOUNT_TRANS?  The cont flags can't really happen here, so it
> won't make a functional difference, but it would document the intent
> much better.

This scaffolding disappears completely in a couple of patches time,
so it's not worth the effort to polishing it to perfection.

> Otherwise looks good:
> 
> Reviewed-by: Christoph Hellwig <[e-mail]>

Thanks!

Patch

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index e5515d0c85c4..f789acd2f755 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -2281,11 +2281,10 @@  xlog_write_calc_vec_length(
 
 	/* Don't account for regions with embedded ophdrs */
 	if (optype && headers > 0) {
-		if (optype & XLOG_UNMOUNT_TRANS)
-			headers--;
+		headers--;
 		if (optype & XLOG_START_TRANS) {
-			ASSERT(headers >= 2);
-			headers -= 2;
+			ASSERT(headers >= 1);
+			headers--;
 		}
 	}
 
@@ -2486,14 +2485,6 @@  xlog_write(
 	int			data_cnt = 0;
 	int			error = 0;
 
-	/*
-	 * If this is a commit or unmount transaction, we don't need a start
-	 * record to be written.  We do, however, have to account for the commit
-	 * header that gets written. Hence we always have to account for an
-	 * extra xlog_op_header here for commit records.
-	 */
-	if (optype & XLOG_COMMIT_TRANS)
-		ticket->t_curr_res -= sizeof(struct xlog_op_header);
 	if (ticket->t_curr_res < 0) {
 		xfs_alert_tag(log->l_mp, XFS_PTAG_LOGRES,
 		     "ctx ticket reservation ran out. Need to up reservation");
@@ -2550,14 +2541,13 @@  xlog_write(
 			/*
 			 * The XLOG_START_TRANS has embedded ophdrs for the
 			 * start record and transaction header. They will always
-			 * be the first two regions in the lv chain.
+			 * be the first two regions in the lv chain. Commit and
+			 * unmount records also have embedded ophdrs.
 			 */
-			if (optype & XLOG_START_TRANS) {
+			if (optype) {
 				ophdr = reg->i_addr;
 				if (index)
 					optype &= ~XLOG_START_TRANS;
-			} else if (optype & XLOG_UNMOUNT_TRANS) {
-				ophdr = reg->i_addr;
 			} else {
 				ophdr = xlog_write_setup_ophdr(log, ptr,
 							ticket, optype);
diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
index 560af08d81dc..56c456263639 100644
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c
@@ -810,9 +810,14 @@  xlog_cil_write_commit_record(
 	struct xfs_cil_ctx	*ctx)
 {
 	struct xlog		*log = ctx->cil->xc_log;
+	struct xlog_op_header	ophdr = {
+		.oh_clientid = XFS_TRANSACTION,
+		.oh_tid = cpu_to_be32(ctx->ticket->t_tid),
+		.oh_flags = XLOG_COMMIT_TRANS,
+	};
 	struct xfs_log_iovec	reg = {
-		.i_addr = NULL,
-		.i_len = 0,
+		.i_addr = &ophdr,
+		.i_len = sizeof(struct xlog_op_header),
 		.i_type = XLOG_REG_TYPE_COMMIT,
 	};
 	struct xfs_log_vec	vec = {
@@ -828,6 +833,8 @@  xlog_cil_write_commit_record(
 	if (error)
 		return error;
 
+	/* account for space used by record data */
+	ctx->ticket->t_curr_res -= reg.i_len;
 	error = xlog_write(log, ctx, &vec, ctx->ticket, XLOG_COMMIT_TRANS);
 	if (error)
 		xfs_force_shutdown(log->l_mp, SHUTDOWN_LOG_IO_ERROR);