Re: [PATCH 27/45] xfs: pass lv chain length into xlog_write()

Darrick J. Wong
2021-03-09T02:37:55Z

On Fri, Mar 05, 2021 at 04:11:25PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> The caller of xlog_write() usually has a close accounting of the
> aggregated vector length contained in the log vector chain passed to
> xlog_write(). There is no need to iterate the chain to calculate he
> length of the data in xlog_write_calculate_len() if the caller is
> already iterating that chain to build it.
>
> Passing in the vector length avoids doing an extra chain iteration,
> which can be a significant amount of work given that large CIL
> commits can have hundreds of thousands of vectors attached to the
> chain.
>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
> fs/xfs/xfs_log.c | 37 ++++++-------------------------------
> fs/xfs/xfs_log_cil.c | 18 +++++++++++++-----
> fs/xfs/xfs_log_priv.h | 2 +-
> 3 files changed, 20 insertions(+), 37 deletions(-)
>
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index 412b167d8d0e..22f97914ab99 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
> @@ -858,7 +858,8 @@ xlog_write_unmount_record(
> */
> if (log->l_targ != log->l_mp->m_ddev_targp)
> blkdev_issue_flush(log->l_targ->bt_bdev);
> - return xlog_write(log, &vec, ticket, NULL, NULL, XLOG_UNMOUNT_TRANS);
> + return xlog_write(log, &vec, ticket, NULL, NULL, XLOG_UNMOUNT_TRANS,
> + reg.i_len);
> }
>
> /*
> @@ -1577,7 +1578,8 @@ xlog_commit_record(
>
> /* account for space used by record data */
> ticket->t_curr_res -= reg.i_len;
> - error = xlog_write(log, &vec, ticket, lsn, iclog, XLOG_COMMIT_TRANS);
> + error = xlog_write(log, &vec, ticket, lsn, iclog, XLOG_COMMIT_TRANS,
> + reg.i_len);
> if (error)
> xfs_force_shutdown(log->l_mp, SHUTDOWN_LOG_IO_ERROR);
> return error;
> @@ -2097,32 +2099,6 @@ xlog_print_trans(
> }
> }
>
> -/*
> - * Calculate the potential space needed by the log vector. All regions contain
> - * their own opheaders and they are accounted for in region space so we don't
> - * need to add them to the vector length here.
> - */
> -static int
> -xlog_write_calc_vec_length(
> - struct xlog_ticket *ticket,
> - struct xfs_log_vec *log_vector,
> - uint optype)
> -{
> - struct xfs_log_vec *lv;
> - int len = 0;
> - int i;
> -
> - 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)
> - continue;
> -
> - for (i = 0; i < lv->lv_niovecs; i++)
> - len += lv->lv_iovecp[i].i_len;
> - }
> - return len;
> -}
> -
> static xlog_op_header_t *
> xlog_write_setup_ophdr(
> struct xlog_op_header *ophdr,
> @@ -2285,13 +2261,13 @@ xlog_write(
> struct xlog_ticket *ticket,
> xfs_lsn_t *start_lsn,
> struct xlog_in_core **commit_iclog,
> - uint optype)
> + uint optype,
> + uint32_t len)
> {
> struct xlog_in_core *iclog = NULL;
> struct xfs_log_vec *lv = log_vector;
> struct xfs_log_iovec *vecp = lv->lv_iovecp;
> int index = 0;
> - int len;
> int partial_copy = 0;
> int partial_copy_len = 0;
> int contwr = 0;
> @@ -2306,7 +2282,6 @@ xlog_write(
> xfs_force_shutdown(log->l_mp, SHUTDOWN_LOG_IO_ERROR);
> }
>
> - 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)) {
> diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
> index 7a5e6bdb7876..34abc3bae587 100644
> --- a/fs/xfs/xfs_log_cil.c
> +++ b/fs/xfs/xfs_log_cil.c
> @@ -710,11 +710,12 @@ xlog_cil_build_trans_hdr(
> sizeof(struct xfs_trans_header);
> hdr->lhdr[1].i_type = XLOG_REG_TYPE_TRANSHDR;
>
> - tic->t_curr_res -= hdr->lhdr[0].i_len + hdr->lhdr[1].i_len;
> -
> lvhdr->lv_niovecs = 2;
> lvhdr->lv_iovecp = &hdr->lhdr[0];
> + lvhdr->lv_bytes = hdr->lhdr[0].i_len + hdr->lhdr[1].i_len;

Er... does this code change belong in an earlier patch? Or if not, why
wasn't it important to set lv_bytes here?

> lvhdr->lv_next = ctx->lv_chain;
> +
> + tic->t_curr_res -= lvhdr->lv_bytes;
> }
>
> /*
> @@ -742,7 +743,8 @@ xlog_cil_push_work(
> struct xfs_log_vec *lv;
> struct xfs_cil_ctx *new_ctx;
> struct xlog_in_core *commit_iclog;
> - int num_iovecs;
> + int num_iovecs = 0;
> + int num_bytes = 0;
> int error = 0;
> struct xlog_cil_trans_hdr thdr;
> struct xfs_log_vec lvhdr = { NULL };
> @@ -841,7 +843,6 @@ xlog_cil_push_work(
> * by the flush lock.
> */
> lv = NULL;
> - num_iovecs = 0;
> while (!list_empty(&cil->xc_cil)) {
> struct xfs_log_item *item;
>
> @@ -855,6 +856,10 @@ xlog_cil_push_work(
> lv = item->li_lv;
> item->li_lv = NULL;
> num_iovecs += lv->lv_niovecs;
> +
> + /* we don't write ordered log vectors */
> + if (lv->lv_buf_len != XFS_LOG_VEC_ORDERED)
> + num_bytes += lv->lv_bytes;
> }
>
> /*
> @@ -893,6 +898,9 @@ xlog_cil_push_work(
> * transaction header here as it is not accounted for in xlog_write().
> */
> xlog_cil_build_trans_hdr(ctx, &thdr, &lvhdr, num_iovecs);
> + num_iovecs += lvhdr.lv_niovecs;
> + num_bytes += lvhdr.lv_bytes;
> +
>

No need to have two blank lines here.

--D

> /*
> * Before we format and submit the first iclog, we have to ensure that
> @@ -907,7 +915,7 @@ xlog_cil_push_work(
> * write head.
> */
> error = xlog_write(log, &lvhdr, ctx->ticket, &ctx->start_lsn, NULL,
> - XLOG_START_TRANS);
> + XLOG_START_TRANS, num_bytes);
> if (error)
> goto out_abort_free_ticket;
>
> diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
> index 8ee6a5f74396..003c11653955 100644
> --- a/fs/xfs/xfs_log_priv.h
> +++ b/fs/xfs/xfs_log_priv.h
> @@ -462,7 +462,7 @@ 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 optype);
> + struct xlog_in_core **commit_iclog, uint optype, uint32_t len);
> int xlog_commit_record(struct xlog *log, struct xlog_ticket *ticket,
> struct xlog_in_core **iclog, xfs_lsn_t *lsn);
> void xlog_state_switch_iclogs(struct xlog *log, struct xlog_in_core *iclog,
> --
> 2.28.0
>