On Wed, May 19, 2021 at 10:12:52PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
> Remove another case where xlog_write() has to prepend an opheader to
> a log transaction. The unmount record + ophdr is smaller than the
> minimum amount of space guaranteed to be free in an iclog (2 *
> sizeof(ophdr)) and so we don't have to care about an unmount record
> being split across 2 iclogs.
>
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
I love me some BUILD_BUG_ON, so
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
--D
> ---
> fs/xfs/xfs_log.c | 39 ++++++++++++++++++++++++++++-----------
> 1 file changed, 28 insertions(+), 11 deletions(-)
>
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index 981cd6f8f0ff..e7a135ffa66f 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
> @@ -800,12 +800,22 @@ xlog_write_unmount_record(
> struct xlog *log,
> struct xlog_ticket *ticket)
> {
> - struct xfs_unmount_log_format ulf = {
> - .magic = XLOG_UNMOUNT_TYPE,
> + struct {
> + struct xlog_op_header ophdr;
> + struct xfs_unmount_log_format ulf;
> + } unmount_rec = {
> + .ophdr = {
> + .oh_clientid = XFS_LOG,
> + .oh_tid = cpu_to_be32(ticket->t_tid),
> + .oh_flags = XLOG_UNMOUNT_TRANS,
> + },
> + .ulf = {
> + .magic = XLOG_UNMOUNT_TYPE,
> + },
> };
> struct xfs_log_iovec reg = {
> - .i_addr = &ulf,
> - .i_len = sizeof(ulf),
> + .i_addr = &unmount_rec,
> + .i_len = sizeof(unmount_rec),
> .i_type = XLOG_REG_TYPE_UNMOUNT,
> };
> struct xfs_log_vec vec = {
> @@ -813,8 +823,12 @@ xlog_write_unmount_record(
> .lv_iovecp = ®,
> };
>
> + BUILD_BUG_ON((sizeof(struct xlog_op_header) +
> + sizeof(struct xfs_unmount_log_format)) !=
> + sizeof(unmount_rec));
> +
> /* account for space used by record data */
> - ticket->t_curr_res -= sizeof(ulf);
> + ticket->t_curr_res -= sizeof(unmount_rec);
>
> /*
> * For external log devices, we need to flush the data device cache
> @@ -2145,6 +2159,8 @@ xlog_write_calc_vec_length(
>
> /* Don't account for regions with embedded ophdrs */
> if (optype && headers > 0) {
> + if (optype & XLOG_UNMOUNT_TRANS)
> + headers--;
> if (optype & XLOG_START_TRANS) {
> ASSERT(headers >= 2);
> headers -= 2;
> @@ -2359,12 +2375,11 @@ xlog_write(
>
> /*
> * 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 or unmount header that gets written. Hence we always have
> - * to account for an extra xlog_op_header here for commit and unmount
> - * records.
> + * 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 | XLOG_UNMOUNT_TRANS))
> + 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,
> @@ -2424,6 +2439,8 @@ xlog_write(
> 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);
> @@ -2454,7 +2471,7 @@ xlog_write(
> /*
> * Copy region.
> *
> - * Commit and unmount records just log an opheader, so
> + * Commit records just log an opheader, so
> * we can have empty payloads with no data region to
> * copy. Hence we only copy the payload if the vector
> * says it has data to copy.
> --
> 2.31.1
>
