Re: [PATCH v2 2/2] xfs: clean up calculation of LR header blocks

Brian Foster
2020-09-04T11:27:23Z

On Fri, Sep 04, 2020 at 04:25:16PM +0800, Gao Xiang wrote:
> Let's use DIV_ROUND_UP() to calculate log record header
> blocks as what did in xlog_get_iclog_buffer_size() and
> wrap up common helpers for log recovery.
>
> Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
> ---
> v1: https://lore.kernel.org/r/20200902140923.24392-1-hsiangkao@redhat.com
>
> changes since v1:
> - add another helper xlog_logrec_hblks() for the cases with
> xfs_sb_version_haslogv2(), and use xlog_logrecv2_hblks()
> for the case of xlog_do_recovery_pass() since it has more
> complex logic other than just calculate hblks...
>
> fs/xfs/xfs_log.c | 4 +--
> fs/xfs/xfs_log_recover.c | 53 ++++++++++++++++------------------------
> 2 files changed, 22 insertions(+), 35 deletions(-)
>
...
> diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
> index 28d952794bfa..c6163065f6e0 100644
> --- a/fs/xfs/xfs_log_recover.c
> +++ b/fs/xfs/xfs_log_recover.c
> @@ -397,6 +397,23 @@ xlog_find_verify_cycle(
> return error;
> }
>
> +static inline int xlog_logrecv2_hblks(struct xlog_rec_header *rh)
> +{
> + int h_size = be32_to_cpu(rh->h_size);
> +
> + if ((be32_to_cpu(rh->h_version) & XLOG_VERSION_2) &&
> + h_size > XLOG_HEADER_CYCLE_SIZE)
> + return DIV_ROUND_UP(h_size, XLOG_HEADER_CYCLE_SIZE);
> + return 1;
> +}
> +
> +static inline int xlog_logrec_hblks(struct xlog *log, xlog_rec_header_t *rh)
> +{
> + if (!xfs_sb_version_haslogv2(&log->l_mp->m_sb))
> + return 1;
> + return xlog_logrecv2_hblks(rh);
> +}
> +

h_version is assigned based on xfs_sb_version_haslogv2() in the first
place so I'm not sure I see the need for multiple helpers like this, at
least with the current code. I can't really speak to why some code
checks the feature bit and/or the record header version and not the
other way around, but perhaps there's some historical reason I'm not
aware of. Regardless, is there ever a case where
xfs_sb_version_haslogv2() == true and h_version != 2? That strikes me as
more of a corruption scenario than anything..

Brian

> /*
> * Potentially backup over partial log record write.
> *
> @@ -489,15 +506,7 @@ xlog_find_verify_log_record(
> * reset last_blk. Only when last_blk points in the middle of a log
> * record do we update last_blk.
> */
> - if (xfs_sb_version_haslogv2(&log->l_mp->m_sb)) {
> - uint h_size = be32_to_cpu(head->h_size);
> -
> - xhdrs = h_size / XLOG_HEADER_CYCLE_SIZE;
> - if (h_size % XLOG_HEADER_CYCLE_SIZE)
> - xhdrs++;
> - } else {
> - xhdrs = 1;
> - }
> + xhdrs = xlog_logrec_hblks(log, head);
>
> if (*last_blk - i + extra_bblks !=
> BTOBB(be32_to_cpu(head->h_len)) + xhdrs)
> @@ -1184,22 +1193,7 @@ xlog_check_unmount_rec(
> * below. We won't want to clear the unmount record if there is one, so
> * we pass the lsn of the unmount record rather than the block after it.
> */
> - if (xfs_sb_version_haslogv2(&log->l_mp->m_sb)) {
> - int h_size = be32_to_cpu(rhead->h_size);
> - int h_version = be32_to_cpu(rhead->h_version);
> -
> - if ((h_version & XLOG_VERSION_2) &&
> - (h_size > XLOG_HEADER_CYCLE_SIZE)) {
> - hblks = h_size / XLOG_HEADER_CYCLE_SIZE;
> - if (h_size % XLOG_HEADER_CYCLE_SIZE)
> - hblks++;
> - } else {
> - hblks = 1;
> - }
> - } else {
> - hblks = 1;
> - }
> -
> + hblks = xlog_logrec_hblks(log, rhead);
> after_umount_blk = xlog_wrap_logbno(log,
> rhead_blk + hblks + BTOBB(be32_to_cpu(rhead->h_len)));
>
> @@ -3024,15 +3018,10 @@ xlog_do_recovery_pass(
> if (error)
> goto bread_err1;
>
> - if ((be32_to_cpu(rhead->h_version) & XLOG_VERSION_2) &&
> - (h_size > XLOG_HEADER_CYCLE_SIZE)) {
> - hblks = h_size / XLOG_HEADER_CYCLE_SIZE;
> - if (h_size % XLOG_HEADER_CYCLE_SIZE)
> - hblks++;
> + hblks = xlog_logrecv2_hblks(rhead);
> + if (hblks != 1) {
> kmem_free(hbp);
> hbp = xlog_alloc_buffer(log, hblks);
> - } else {
> - hblks = 1;
> }
> } else {
> ASSERT(log->l_sectBBsize == 1);
> --
> 2.18.1
>