Re: [PATCH 1/2] xfs: number the cache flushes submitted to each buftarg

[Brian Foster <bfoster@redhat.com>]

On Thu, Nov 05, 2026 at 11:49:12AM +0900, Daejun Park via B4 Relay wrote:
> From: Daejun Park <daejun7.park@samsung.com>
> 
> fsync can only skip its own cache flush when its log force wrote out
> the iclog. It cannot tell whether a flush that another task submitted
> covers its data.
> 
> Number the cache flushes that the log code submits to each buftarg,
> and record the highest number that completed without error. Nothing
> reads the numbers yet.
> 
> Signed-off-by: Daejun Park <daejun7.park@samsung.com>
> ---
>  fs/xfs/xfs_buf.c      | 13 +++++++++++++
>  fs/xfs/xfs_buf.h      | 21 +++++++++++++++++++++
>  fs/xfs/xfs_log.c      | 25 +++++++++++++++++++------
>  fs/xfs/xfs_log_priv.h |  1 +
>  4 files changed, 54 insertions(+), 6 deletions(-)
> 
...
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index 74b324f915a..734daa4e99b 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
...
> @@ -1688,6 +1698,9 @@ xlog_write_iclog(
>  		iclog->ic_bio.bi_opf |= REQ_PREFLUSH;
>  	if (iclog->ic_flags & XLOG_ICL_NEED_FUA)
>  		iclog->ic_bio.bi_opf |= REQ_FUA;
> +	iclog->ic_flush_seq = 0;
> +	if (iclog->ic_bio.bi_opf & REQ_PREFLUSH)
> +		iclog->ic_flush_seq = xfs_buftarg_flush_start(log->l_targ);

Bit of a nit, but it looks like this would be cleaner if we moved both
of these a bit further up. I.e., zero ->ic_flush_seq right after where
we init the iclog->ic_bio fields, and then move the assignment under the
same block where we set the PREFLUSH flag. Hm?

Brian

>  
>  	iclog->ic_flags &= ~(XLOG_ICL_NEED_FLUSH | XLOG_ICL_NEED_FLUSH_LOG |
>  			     XLOG_ICL_NEED_FUA);
> diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
> index 529720a4984..df0f13c4e04 100644
> --- a/fs/xfs/xfs_log_priv.h
> +++ b/fs/xfs/xfs_log_priv.h
> @@ -222,6 +222,7 @@ struct xlog_in_core {
>  #endif
>  	struct semaphore	ic_sema;
>  	struct work_struct	ic_end_io_work;
> +	s64			ic_flush_seq;	/* buftarg flush number */
>  	struct bio		ic_bio;
>  	struct bio_vec		ic_bvec[];
>  };
> 
> -- 
> 2.43.0
> 
> 
>