diff mbox series

[07/45] xfs: remove need_start_rec parameter from xlog_write()

Message ID 20210305051143.182133-8-david@fromorbit.com (mailing list archive)
State Superseded
Headers show
Series xfs: consolidated log and optimisation changes | expand

Commit Message

Dave Chinner March 5, 2021, 5:11 a.m. UTC 
From: Dave Chinner <dchinner@redhat.com>

The CIL push is the only call to xlog_write that sets this variable
to true. The other callers don't need a start rec, and they tell
xlog_write what to do by passing the type of ophdr they need written
in the flags field. The need_start_rec parameter essentially tells
xlog_write to to write an extra ophdr with a XLOG_START_TRANS type,
so get rid of the variable to do this and pass XLOG_START_TRANS as
the flag value into xlog_write() from the CIL push.

$ size fs/xfs/xfs_log.o*
  text	   data	    bss	    dec	    hex	filename
 27595	    560	      8	  28163	   6e03	fs/xfs/xfs_log.o.orig
 27454	    560	      8	  28022	   6d76	fs/xfs/xfs_log.o.patched

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
---
 fs/xfs/xfs_log.c      | 44 +++++++++++++++++++++----------------------
 fs/xfs/xfs_log_cil.c  |  3 ++-
 fs/xfs/xfs_log_priv.h |  3 +--
 3 files changed, 25 insertions(+), 25 deletions(-)

Comments

Brian Foster March 15, 2021, 2:45 p.m. UTC | #1 
On Fri, Mar 05, 2021 at 04:11:05PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> The CIL push is the only call to xlog_write that sets this variable
> to true. The other callers don't need a start rec, and they tell
> xlog_write what to do by passing the type of ophdr they need written
> in the flags field. The need_start_rec parameter essentially tells
> xlog_write to to write an extra ophdr with a XLOG_START_TRANS type,
> so get rid of the variable to do this and pass XLOG_START_TRANS as
> the flag value into xlog_write() from the CIL push.
> 
> $ size fs/xfs/xfs_log.o*
>   text	   data	    bss	    dec	    hex	filename
>  27595	    560	      8	  28163	   6e03	fs/xfs/xfs_log.o.orig
>  27454	    560	      8	  28022	   6d76	fs/xfs/xfs_log.o.patched
> 
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
> ---
>  fs/xfs/xfs_log.c      | 44 +++++++++++++++++++++----------------------
>  fs/xfs/xfs_log_cil.c  |  3 ++-
>  fs/xfs/xfs_log_priv.h |  3 +--
>  3 files changed, 25 insertions(+), 25 deletions(-)
> 
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index fee76c485727..364694a83de6 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
...
> @@ -2449,13 +2448,15 @@ xlog_write(
>  			 * write a start record. Only do this for the first
>  			 * iclog we write to.
>  			 */
> -			if (need_start_rec) {
> +			if (optype & XLOG_START_TRANS) {
>  				xlog_write_start_rec(ptr, ticket);
>  				xlog_write_adv_cnt(&ptr, &len, &log_offset,
>  						sizeof(struct xlog_op_header));
> +				optype &= ~XLOG_START_TRANS;
> +				wrote_start_rec = true;

I think this overload of optype and op header flags is sufficiently
subtle and fragile that this warrants a comment. E.g., something like:

"Now that we've written the start record, we must clear the flag now so
it doesn't leak into subsequent op headers."

Otherwise, I think it's pretty much a guarantee that somebody will come
along later and attempt to optimize away what looks like an unnecessary
boolean by moving the flag clear further down without realizing why it's
here.

In fact, I think what would have been more clean and simple overall is
to translate the new optype param back into the preexisting flags (as a
local variable) and need_start_rec parameters right after optype is
consumed by xlog_write_calc_vec_length(). Then we wouldn't have to tweak
as much functional logic to accommodate a subtle variable overload
(i.e., basically just removing code changes from this patch) and the
code would be self explanatory. That said, the remaining changes look Ok
to me so long as the above is clearly documented.

Brian

>  			}
>  
> -			ophdr = xlog_write_setup_ophdr(log, ptr, ticket, flags);
> +			ophdr = xlog_write_setup_ophdr(log, ptr, ticket, optype);
>  			if (!ophdr)
>  				return -EIO;
>  
> @@ -2486,14 +2487,13 @@ xlog_write(
>  			}
>  			copy_len += sizeof(struct xlog_op_header);
>  			record_cnt++;
> -			if (need_start_rec) {
> +			if (wrote_start_rec) {
>  				copy_len += sizeof(struct xlog_op_header);
>  				record_cnt++;
> -				need_start_rec = false;
>  			}
>  			data_cnt += contwr ? copy_len : 0;
>  
> -			error = xlog_write_copy_finish(log, iclog, flags,
> +			error = xlog_write_copy_finish(log, iclog, optype,
>  						       &record_cnt, &data_cnt,
>  						       &partial_copy,
>  						       &partial_copy_len,
> @@ -2537,7 +2537,7 @@ xlog_write(
>  	spin_lock(&log->l_icloglock);
>  	xlog_state_finish_copy(log, iclog, record_cnt, data_cnt);
>  	if (commit_iclog) {
> -		ASSERT(flags & XLOG_COMMIT_TRANS);
> +		ASSERT(optype & XLOG_COMMIT_TRANS);
>  		*commit_iclog = iclog;
>  	} else {
>  		error = xlog_state_release_iclog(log, iclog);
> diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
> index b4cdb8b6c4c3..c04d5d37a3a2 100644
> --- a/fs/xfs/xfs_log_cil.c
> +++ b/fs/xfs/xfs_log_cil.c
> @@ -829,7 +829,8 @@ xlog_cil_push_work(
>  	 */
>  	wait_for_completion(&bdev_flush);
>  
> -	error = xlog_write(log, &lvhdr, tic, &ctx->start_lsn, NULL, 0, true);
> +	error = xlog_write(log, &lvhdr, tic, &ctx->start_lsn, NULL,
> +				XLOG_START_TRANS);
>  	if (error)
>  		goto out_abort_free_ticket;
>  
> diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
> index ee7786b33da9..56e1942c47df 100644
> --- a/fs/xfs/xfs_log_priv.h
> +++ b/fs/xfs/xfs_log_priv.h
> @@ -480,8 +480,7 @@ void	xlog_print_tic_res(struct xfs_mount *mp, struct xlog_ticket *ticket);
>  void	xlog_print_trans(struct xfs_trans *);
>  int	xlog_write(struct xlog *log, struct xfs_log_vec *log_vector,
>  		struct xlog_ticket *tic, xfs_lsn_t *start_lsn,
> -		struct xlog_in_core **commit_iclog, uint flags,
> -		bool need_start_rec);
> +		struct xlog_in_core **commit_iclog, uint optype);
>  int	xlog_commit_record(struct xlog *log, struct xlog_ticket *ticket,
>  		struct xlog_in_core **iclog, xfs_lsn_t *lsn);
>  void	xfs_log_ticket_ungrant(struct xlog *log, struct xlog_ticket *ticket);
> -- 
> 2.28.0
>
Christoph Hellwig March 16, 2021, 2:15 p.m. UTC | #2 
> @@ -818,9 +818,7 @@ xlog_wait_on_iclog(
>  static int
>  xlog_write_unmount_record(
>  	struct xlog		*log,
> -	struct xlog_ticket	*ticket,
> -	xfs_lsn_t		*lsn,
> -	uint			flags)
> +	struct xlog_ticket	*ticket)
>  {
>  	struct xfs_unmount_log_format ulf = {
>  		.magic = XLOG_UNMOUNT_TYPE,
> @@ -837,7 +835,7 @@ xlog_write_unmount_record(
>  
>  	/* account for space used by record data */
>  	ticket->t_curr_res -= sizeof(ulf);
> -	return xlog_write(log, &vec, ticket, lsn, NULL, flags, false);
> +	return xlog_write(log, &vec, ticket, NULL, NULL, XLOG_UNMOUNT_TRANS);

The removal of the lsn argument from xlog_write_unmount_record and
making optional of the start_lsn argument to xlog_write is not
documented anywhere.  I still it would be best to split such tiny
argument passing cleanups from a more complicated and not quite trivial
one, but at very least it needs to be clearly documented.
diff mbox series

Patch

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index fee76c485727..364694a83de6 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -818,9 +818,7 @@  xlog_wait_on_iclog(
 static int
 xlog_write_unmount_record(
 	struct xlog		*log,
-	struct xlog_ticket	*ticket,
-	xfs_lsn_t		*lsn,
-	uint			flags)
+	struct xlog_ticket	*ticket)
 {
 	struct xfs_unmount_log_format ulf = {
 		.magic = XLOG_UNMOUNT_TYPE,
@@ -837,7 +835,7 @@  xlog_write_unmount_record(
 
 	/* account for space used by record data */
 	ticket->t_curr_res -= sizeof(ulf);
-	return xlog_write(log, &vec, ticket, lsn, NULL, flags, false);
+	return xlog_write(log, &vec, ticket, NULL, NULL, XLOG_UNMOUNT_TRANS);
 }
 
 /*
@@ -851,15 +849,13 @@  xlog_unmount_write(
 	struct xfs_mount	*mp = log->l_mp;
 	struct xlog_in_core	*iclog;
 	struct xlog_ticket	*tic = NULL;
-	xfs_lsn_t		lsn;
-	uint			flags = XLOG_UNMOUNT_TRANS;
 	int			error;
 
 	error = xfs_log_reserve(mp, 600, 1, &tic, XFS_LOG, 0);
 	if (error)
 		goto out_err;
 
-	error = xlog_write_unmount_record(log, tic, &lsn, flags);
+	error = xlog_write_unmount_record(log, tic);
 	/*
 	 * At this point, we're umounting anyway, so there's no point in
 	 * transitioning log state to IOERROR. Just continue...
@@ -1551,8 +1547,7 @@  xlog_commit_record(
 	if (XLOG_FORCED_SHUTDOWN(log))
 		return -EIO;
 
-	error = xlog_write(log, &vec, ticket, lsn, iclog, XLOG_COMMIT_TRANS,
-			   false);
+	error = xlog_write(log, &vec, ticket, lsn, iclog, XLOG_COMMIT_TRANS);
 	if (error)
 		xfs_force_shutdown(log->l_mp, SHUTDOWN_LOG_IO_ERROR);
 	return error;
@@ -2149,13 +2144,16 @@  static int
 xlog_write_calc_vec_length(
 	struct xlog_ticket	*ticket,
 	struct xfs_log_vec	*log_vector,
-	bool			need_start_rec)
+	uint			optype)
 {
 	struct xfs_log_vec	*lv;
-	int			headers = need_start_rec ? 1 : 0;
+	int			headers = 0;
 	int			len = 0;
 	int			i;
 
+	if (optype & XLOG_START_TRANS)
+		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)
@@ -2375,8 +2373,7 @@  xlog_write(
 	struct xlog_ticket	*ticket,
 	xfs_lsn_t		*start_lsn,
 	struct xlog_in_core	**commit_iclog,
-	uint			flags,
-	bool			need_start_rec)
+	uint			optype)
 {
 	struct xlog_in_core	*iclog = NULL;
 	struct xfs_log_vec	*lv = log_vector;
@@ -2404,8 +2401,9 @@  xlog_write(
 		xfs_force_shutdown(log->l_mp, SHUTDOWN_LOG_IO_ERROR);
 	}
 
-	len = xlog_write_calc_vec_length(ticket, log_vector, need_start_rec);
-	*start_lsn = 0;
+	len = xlog_write_calc_vec_length(ticket, log_vector, optype);
+	if (start_lsn)
+		*start_lsn = 0;
 	while (lv && (!lv->lv_niovecs || index < lv->lv_niovecs)) {
 		void		*ptr;
 		int		log_offset;
@@ -2419,7 +2417,7 @@  xlog_write(
 		ptr = iclog->ic_datap + log_offset;
 
 		/* start_lsn is the first lsn written to. That's all we need. */
-		if (!*start_lsn)
+		if (start_lsn && !*start_lsn)
 			*start_lsn = be64_to_cpu(iclog->ic_header.h_lsn);
 
 		/*
@@ -2432,6 +2430,7 @@  xlog_write(
 			int			copy_len;
 			int			copy_off;
 			bool			ordered = false;
+			bool			wrote_start_rec = false;
 
 			/* ordered log vectors have no regions to write */
 			if (lv->lv_buf_len == XFS_LOG_VEC_ORDERED) {
@@ -2449,13 +2448,15 @@  xlog_write(
 			 * write a start record. Only do this for the first
 			 * iclog we write to.
 			 */
-			if (need_start_rec) {
+			if (optype & XLOG_START_TRANS) {
 				xlog_write_start_rec(ptr, ticket);
 				xlog_write_adv_cnt(&ptr, &len, &log_offset,
 						sizeof(struct xlog_op_header));
+				optype &= ~XLOG_START_TRANS;
+				wrote_start_rec = true;
 			}
 
-			ophdr = xlog_write_setup_ophdr(log, ptr, ticket, flags);
+			ophdr = xlog_write_setup_ophdr(log, ptr, ticket, optype);
 			if (!ophdr)
 				return -EIO;
 
@@ -2486,14 +2487,13 @@  xlog_write(
 			}
 			copy_len += sizeof(struct xlog_op_header);
 			record_cnt++;
-			if (need_start_rec) {
+			if (wrote_start_rec) {
 				copy_len += sizeof(struct xlog_op_header);
 				record_cnt++;
-				need_start_rec = false;
 			}
 			data_cnt += contwr ? copy_len : 0;
 
-			error = xlog_write_copy_finish(log, iclog, flags,
+			error = xlog_write_copy_finish(log, iclog, optype,
 						       &record_cnt, &data_cnt,
 						       &partial_copy,
 						       &partial_copy_len,
@@ -2537,7 +2537,7 @@  xlog_write(
 	spin_lock(&log->l_icloglock);
 	xlog_state_finish_copy(log, iclog, record_cnt, data_cnt);
 	if (commit_iclog) {
-		ASSERT(flags & XLOG_COMMIT_TRANS);
+		ASSERT(optype & XLOG_COMMIT_TRANS);
 		*commit_iclog = iclog;
 	} else {
 		error = xlog_state_release_iclog(log, iclog);
diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
index b4cdb8b6c4c3..c04d5d37a3a2 100644
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c
@@ -829,7 +829,8 @@  xlog_cil_push_work(
 	 */
 	wait_for_completion(&bdev_flush);
 
-	error = xlog_write(log, &lvhdr, tic, &ctx->start_lsn, NULL, 0, true);
+	error = xlog_write(log, &lvhdr, tic, &ctx->start_lsn, NULL,
+				XLOG_START_TRANS);
 	if (error)
 		goto out_abort_free_ticket;
 
diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index ee7786b33da9..56e1942c47df 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -480,8 +480,7 @@  void	xlog_print_tic_res(struct xfs_mount *mp, struct xlog_ticket *ticket);
 void	xlog_print_trans(struct xfs_trans *);
 int	xlog_write(struct xlog *log, struct xfs_log_vec *log_vector,
 		struct xlog_ticket *tic, xfs_lsn_t *start_lsn,
-		struct xlog_in_core **commit_iclog, uint flags,
-		bool need_start_rec);
+		struct xlog_in_core **commit_iclog, uint optype);
 int	xlog_commit_record(struct xlog *log, struct xlog_ticket *ticket,
 		struct xlog_in_core **iclog, xfs_lsn_t *lsn);
 void	xfs_log_ticket_ungrant(struct xlog *log, struct xlog_ticket *ticket);