Re: [PATCH RFC 2/2] xfs: don't log dirty ranges for ordered buffers

Darrick J. Wong
2017-08-16T17:15:07Z

On Mon, Aug 14, 2017 at 12:54:51PM -0400, Brian Foster wrote:
> Ordered buffers are attached to transactions and pushed through the
> logging infrastructure just like normal buffers with the exception
> that they are not actually written to the log. Therefore, we don't
> need to log dirty ranges of ordered buffers. xfs_trans_log_buf() is
> called on ordered buffers to set up all of the dirty state on the
> transaction, buffer and log item and prepare the buffer for I/O.
>
> Now that xfs_trans_dirty_buf() is available, call it from
> xfs_trans_ordered_buf() so the latter is now mutually exclusive with
> xfs_trans_log_buf(). This reflects the implementation of ordered
> buffers and helps eliminate confusion over the need to log ranges of
> ordered buffers just to set up internal log state.
>
> Signed-off-by: Brian Foster <bfoster@redhat.com>
> ---
> fs/xfs/libxfs/xfs_btree.c | 3 ++-
> fs/xfs/libxfs/xfs_ialloc.c | 2 --
> fs/xfs/xfs_trans_buf.c | 25 +++++++++++++------------
> 3 files changed, 15 insertions(+), 15 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
> index e0bcc4a..9c97896 100644
> --- a/fs/xfs/libxfs/xfs_btree.c
> +++ b/fs/xfs/libxfs/xfs_btree.c
> @@ -4466,7 +4466,8 @@ xfs_btree_block_change_owner(
> if (bp) {
> if (cur->bc_tp) {
> xfs_trans_ordered_buf(cur->bc_tp, bp);
> - xfs_btree_log_block(cur, bp, XFS_BB_OWNER);
> + /*xfs_trans_buf_set_type(cur->bc_tp, bp,
> + XFS_BLFT_BTREE_BUF);*/

I don't see the point of this, but maybe you've already dropped it anyway. :)

> } else {
> xfs_buf_delwri_queue(bp, bbcoi->buffer_list);
> }
> diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
> index ffd5a15..12c0452 100644
> --- a/fs/xfs/libxfs/xfs_ialloc.c
> +++ b/fs/xfs/libxfs/xfs_ialloc.c
> @@ -378,8 +378,6 @@ xfs_ialloc_inode_init(
> * transaction and pin the log appropriately.
> */
> xfs_trans_ordered_buf(tp, fbuf);
> - xfs_trans_log_buf(tp, fbuf, 0,
> - BBTOB(fbuf->b_length) - 1);
> }
> } else {
> fbuf->b_flags |= XBF_DONE;
> diff --git a/fs/xfs/xfs_trans_buf.c b/fs/xfs/xfs_trans_buf.c
> index 58818a0..3a358cb 100644
> --- a/fs/xfs/xfs_trans_buf.c
> +++ b/fs/xfs/xfs_trans_buf.c
> @@ -560,16 +560,12 @@ xfs_trans_log_buf(
> struct xfs_buf_log_item *bip = bp->b_fspriv;
>
> ASSERT(first <= last && last < BBTOB(bp->b_length));
> + ASSERT(!(bip->bli_flags & XFS_BLI_ORDERED));
>
> xfs_trans_dirty_buf(tp, bp);
>
> - /*
> - * If we have an ordered buffer we are not logging any dirty range but
> - * it still needs to be marked dirty and that it has been logged.
> - */
> trace_xfs_trans_log_buf(bip);
> - if (!(bip->bli_flags & XFS_BLI_ORDERED))
> - xfs_buf_item_log(bip, first, last);
> + xfs_buf_item_log(bip, first, last);
> }
>
>
> @@ -722,12 +718,11 @@ xfs_trans_inode_alloc_buf(
> }
>
> /*
> - * Mark the buffer as ordered for this transaction. This means
> - * that the contents of the buffer are not recorded in the transaction
> - * but it is tracked in the AIL as though it was. This allows us
> - * to record logical changes in transactions rather than the physical
> - * changes we make to the buffer without changing writeback ordering
> - * constraints of metadata buffers.
> + * Mark the buffer as ordered for this transaction. This means that the contents
> + * of the buffer are not recorded in the transaction but it is tracked in the
> + * AIL as though it was. This allows us to record logical changes in
> + * transactions rather than the physical changes we make to the buffer without
> + * changing writeback ordering constraints of metadata buffers.

Did the text of this comment change? AFAICT the only difference is
where we line wrap?

(If that's the case, why bother?)

> */
> void
> xfs_trans_ordered_buf(
> @@ -742,6 +737,12 @@ xfs_trans_ordered_buf(
>
> bip->bli_flags |= XFS_BLI_ORDERED;
> trace_xfs_buf_item_ordered(bip);
> +
> + /*
> + * We don't log a dirty range of an ordered buffer but it still needs
> + * to be marked dirty and that it has been logged.
> + */
> + xfs_trans_dirty_buf(tp, bp);

Otherwise looks ok to me...

--D

> }
>
> /*
> --
> 2.9.4
>
> --
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