Re: [RFC v5 PATCH 7/9] xfs: buffer relogging support prototype

Brian Foster
2020-02-28T14:04:50Z

On Thu, Feb 27, 2020 at 04:33:26PM -0700, Allison Collins wrote:
> On 2/27/20 6:43 AM, Brian Foster wrote:
> > Add a quick and dirty implementation of buffer relogging support.
> > There is currently no use case for buffer relogging. This is for
> > experimental use only and serves as an example to demonstrate the
> > ability to relog arbitrary items in the future, if necessary.
> >
> > Add a hook to enable relogging a buffer in a transaction, update the
> > buffer log item handlers to support relogged BLIs and update the
> > relog handler to join the relogged buffer to the relog transaction.
> >
> Alrighty, thanks for the example! It sounds like it's meant more to be a
> demo than to really be applied though?
>

Yeah, I just wanted to include something that demonstrates how this can
be used for something other than intents, because that concern was
raised on previous versions...

Brian

> Allison
>
> > Signed-off-by: Brian Foster <bfoster@redhat.com>
> > ---
> > fs/xfs/xfs_buf_item.c | 5 +++++
> > fs/xfs/xfs_trans.h | 1 +
> > fs/xfs/xfs_trans_ail.c | 19 ++++++++++++++++---
> > fs/xfs/xfs_trans_buf.c | 22 ++++++++++++++++++++++
> > 4 files changed, 44 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
> > index 663810e6cd59..4ef2725fa8ce 100644
> > --- a/fs/xfs/xfs_buf_item.c
> > +++ b/fs/xfs/xfs_buf_item.c
> > @@ -463,6 +463,7 @@ xfs_buf_item_unpin(
> > list_del_init(&bp->b_li_list);
> > bp->b_iodone = NULL;
> > } else {
> > + xfs_trans_relog_item_cancel(lip, false);
> > spin_lock(&ailp->ail_lock);
> > xfs_trans_ail_delete(ailp, lip, SHUTDOWN_LOG_IO_ERROR);
> > xfs_buf_item_relse(bp);
> > @@ -528,6 +529,9 @@ xfs_buf_item_push(
> > return XFS_ITEM_LOCKED;
> > }
> > + if (test_bit(XFS_LI_RELOG, &lip->li_flags))
> > + return XFS_ITEM_RELOG;
> > +
> > ASSERT(!(bip->bli_flags & XFS_BLI_STALE));
> > trace_xfs_buf_item_push(bip);
> > @@ -956,6 +960,7 @@ STATIC void
> > xfs_buf_item_free(
> > struct xfs_buf_log_item *bip)
> > {
> > + ASSERT(!test_bit(XFS_LI_RELOG, &bip->bli_item.li_flags));
> > xfs_buf_item_free_format(bip);
> > kmem_free(bip->bli_item.li_lv_shadow);
> > kmem_cache_free(xfs_buf_item_zone, bip);
> > diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
> > index 1637df32c64c..81cb42f552d9 100644
> > --- a/fs/xfs/xfs_trans.h
> > +++ b/fs/xfs/xfs_trans.h
> > @@ -226,6 +226,7 @@ void xfs_trans_inode_buf(xfs_trans_t *, struct xfs_buf *);
> > void xfs_trans_stale_inode_buf(xfs_trans_t *, struct xfs_buf *);
> > bool xfs_trans_ordered_buf(xfs_trans_t *, struct xfs_buf *);
> > void xfs_trans_dquot_buf(xfs_trans_t *, struct xfs_buf *, uint);
> > +bool xfs_trans_relog_buf(struct xfs_trans *, struct xfs_buf *);
> > void xfs_trans_inode_alloc_buf(xfs_trans_t *, struct xfs_buf *);
> > void xfs_trans_ichgtime(struct xfs_trans *, struct xfs_inode *, int);
> > void xfs_trans_ijoin(struct xfs_trans *, struct xfs_inode *, uint);
> > diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
> > index 71a47faeaae8..103ab62e61be 100644
> > --- a/fs/xfs/xfs_trans_ail.c
> > +++ b/fs/xfs/xfs_trans_ail.c
> > @@ -18,6 +18,7 @@
> > #include "xfs_error.h"
> > #include "xfs_log.h"
> > #include "xfs_log_priv.h"
> > +#include "xfs_buf_item.h"
> > #ifdef DEBUG
> > /*
> > @@ -187,9 +188,21 @@ xfs_ail_relog(
> > xfs_log_ticket_put(ailp->ail_relog_tic);
> > spin_unlock(&ailp->ail_lock);
> > - xfs_trans_add_item(tp, lip);
> > - set_bit(XFS_LI_DIRTY, &lip->li_flags);
> > - tp->t_flags |= XFS_TRANS_DIRTY;
> > + /*
> > + * TODO: Ideally, relog transaction management would be pushed
> > + * down into the ->iop_push() callbacks rather than playing
> > + * games with ->li_trans and looking at log item types here.
> > + */
> > + if (lip->li_type == XFS_LI_BUF) {
> > + struct xfs_buf_log_item *bli = (struct xfs_buf_log_item *) lip;
> > + xfs_buf_hold(bli->bli_buf);
> > + xfs_trans_bjoin(tp, bli->bli_buf);
> > + xfs_trans_dirty_buf(tp, bli->bli_buf);
> > + } else {
> > + xfs_trans_add_item(tp, lip);
> > + set_bit(XFS_LI_DIRTY, &lip->li_flags);
> > + tp->t_flags |= XFS_TRANS_DIRTY;
> > + }
> > /* XXX: include ticket owner task fix */
> > error = xfs_trans_roll(&tp);
> > ASSERT(!error);
> > diff --git a/fs/xfs/xfs_trans_buf.c b/fs/xfs/xfs_trans_buf.c
> > index 08174ffa2118..e17715ac23fc 100644
> > --- a/fs/xfs/xfs_trans_buf.c
> > +++ b/fs/xfs/xfs_trans_buf.c
> > @@ -787,3 +787,25 @@ xfs_trans_dquot_buf(
> > xfs_trans_buf_set_type(tp, bp, type);
> > }
> > +
> > +/*
> > + * Enable automatic relogging on a buffer. This essentially pins a dirty buffer
> > + * in-core until relogging is disabled. Note that the buffer must not already be
> > + * queued for writeback.
> > + */
> > +bool
> > +xfs_trans_relog_buf(
> > + struct xfs_trans *tp,
> > + struct xfs_buf *bp)
> > +{
> > + struct xfs_buf_log_item *bip = bp->b_log_item;
> > +
> > + ASSERT(tp->t_flags & XFS_TRANS_RELOG);
> > + ASSERT(xfs_buf_islocked(bp));
> > +
> > + if (bp->b_flags & _XBF_DELWRI_Q)
> > + return false;
> > +
> > + xfs_trans_relog_item(&bip->bli_item);
> > + return true;
> > +}
> >
>