On Thu, Oct 01, 2020 at 01:31:42PM -0400, Brian Foster wrote:
> On Tue, Sep 29, 2020 at 10:43:31AM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> >
> > When we replay unfinished intent items that have been recovered from the
> > log, it's possible that the replay will cause the creation of more
> > deferred work items. As outlined in commit 509955823cc9c ("xfs: log
> > recovery should replay deferred ops in order"), later work items have an
> > implicit ordering dependency on earlier work items. Therefore, recovery
> > must replay the items (both recovered and created) in the same order
> > that they would have been during normal operation.
> >
> > For log recovery, we enforce this ordering by using an empty transaction
> > to collect deferred ops that get created in the process of recovering a
> > log intent item to prevent them from being committed before the rest of
> > the recovered intent items. After we finish committing all the
> > recovered log items, we allocate a transaction with an enormous block
> > reservation, splice our huge list of created deferred ops into that
> > transaction, and commit it, thereby finishing all those ops.
> >
> > This is /really/ hokey -- it's the one place in XFS where we allow
> > nested transactions; the splicing of the defer ops list is is inelegant
> > and has to be done twice per recovery function; and the broken way we
> > handle inode pointers and block reservations cause subtle use-after-free
> > and allocator problems that will be fixed by this patch and the two
> > patches after it.
> >
> > Therefore, replace the hokey empty transaction with a structure designed
> > to capture each chain of deferred ops that are created as part of
> > recovering a single unfinished log intent. Finally, refactor the loop
> > that replays those chains to do so using one transaction per chain.
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > ---
> > fs/xfs/libxfs/xfs_defer.c | 89 +++++++++++++++++++++++++++++++--
> > fs/xfs/libxfs/xfs_defer.h | 19 +++++++
> > fs/xfs/xfs_bmap_item.c | 16 +-----
> > fs/xfs/xfs_extfree_item.c | 7 +--
> > fs/xfs/xfs_log_recover.c | 118 +++++++++++++++++++++++++-------------------
> > fs/xfs/xfs_refcount_item.c | 16 +-----
> > fs/xfs/xfs_rmap_item.c | 7 +--
> > fs/xfs/xfs_trans.h | 3 +
> > 8 files changed, 184 insertions(+), 91 deletions(-)
> >
> >
> ...
> > diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
> > index 84f876c6d498..550d0fa8057a 100644
> > --- a/fs/xfs/xfs_log_recover.c
> > +++ b/fs/xfs/xfs_log_recover.c
> > @@ -2434,37 +2434,62 @@ xlog_recover_process_data(
> > /* Take all the collected deferred ops and finish them in order. */
> > static int
> > xlog_finish_defer_ops(
> > - struct xfs_trans *parent_tp)
> > + struct xfs_mount *mp,
> > + struct list_head *capture_list)
> > {
> > - struct xfs_mount *mp = parent_tp->t_mountp;
> > + struct xfs_defer_capture *dfc, *next;
> > struct xfs_trans *tp;
> > int64_t freeblks;
> > - uint resblks;
> > - int error;
> > + uint64_t resblks;
> > + int error = 0;
> >
> > - /*
> > - * We're finishing the defer_ops that accumulated as a result of
> > - * recovering unfinished intent items during log recovery. We
> > - * reserve an itruncate transaction because it is the largest
> > - * permanent transaction type. Since we're the only user of the fs
> > - * right now, take 93% (15/16) of the available free blocks. Use
> > - * weird math to avoid a 64-bit division.
> > - */
> > - freeblks = percpu_counter_sum(&mp->m_fdblocks);
> > - if (freeblks <= 0)
> > - return -ENOSPC;
> > - resblks = min_t(int64_t, UINT_MAX, freeblks);
> > - resblks = (resblks * 15) >> 4;
> > - error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, resblks,
> > - 0, XFS_TRANS_RESERVE, &tp);
> > - if (error)
> > - return error;
> > - /* transfer all collected dfops to this transaction */
> > - xfs_defer_move(tp, parent_tp);
> > + list_for_each_entry_safe(dfc, next, capture_list, dfc_list) {
> > + /*
> > + * We're finishing the defer_ops that accumulated as a result
> > + * of recovering unfinished intent items during log recovery.
> > + * We reserve an itruncate transaction because it is the
> > + * largest permanent transaction type. Since we're the only
> > + * user of the fs right now, take 93% (15/16) of the available
> > + * free blocks. Use weird math to avoid a 64-bit division.
> > + */
> > + freeblks = percpu_counter_sum(&mp->m_fdblocks);
> > + if (freeblks <= 0)
> > + return -ENOSPC;
> >
> > - return xfs_trans_commit(tp);
> > + resblks = min_t(uint64_t, UINT_MAX, freeblks);
> > + resblks = (resblks * 15) >> 4;
> > + error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, resblks,
> > + 0, XFS_TRANS_RESERVE, &tp);
> > + if (error)
> > + return error;
> > +
> > + /* Transfer all collected dfops to this transaction. */
>
> This old comment is a little misleading now that we have per-intent
> capture lists. That nit aside, this looks good to me and the updated
> factoring is easier to follow:
I'll change it to:
/*
* Transfer to this new transaction all the dfops we captured
* from recovering a single intent item.
*/
> Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
Thanks for the review!
--D
>
> > + list_del_init(&dfc->dfc_list);
> > + xfs_defer_ops_continue(dfc, tp);
> > +
> > + error = xfs_trans_commit(tp);
> > + if (error)
> > + return error;
> > + }
> > +
> > + ASSERT(list_empty(capture_list));
> > + return 0;
> > }
> >
> > +/* Release all the captured defer ops and capture structures in this list. */
> > +static void
> > +xlog_abort_defer_ops(
> > + struct xfs_mount *mp,
> > + struct list_head *capture_list)
> > +{
> > + struct xfs_defer_capture *dfc;
> > + struct xfs_defer_capture *next;
> > +
> > + list_for_each_entry_safe(dfc, next, capture_list, dfc_list) {
> > + list_del_init(&dfc->dfc_list);
> > + xfs_defer_ops_release(mp, dfc);
> > + }
> > +}
> > /*
> > * When this is called, all of the log intent items which did not have
> > * corresponding log done items should be in the AIL. What we do now
> > @@ -2485,35 +2510,23 @@ STATIC int
> > xlog_recover_process_intents(
> > struct xlog *log)
> > {
> > - struct xfs_trans *parent_tp;
> > + LIST_HEAD(capture_list);
> > struct xfs_ail_cursor cur;
> > struct xfs_log_item *lip;
> > struct xfs_ail *ailp;
> > - int error;
> > + int error = 0;
> > #if defined(DEBUG) || defined(XFS_WARN)
> > xfs_lsn_t last_lsn;
> > #endif
> >
> > - /*
> > - * The intent recovery handlers commit transactions to complete recovery
> > - * for individual intents, but any new deferred operations that are
> > - * queued during that process are held off until the very end. The
> > - * purpose of this transaction is to serve as a container for deferred
> > - * operations. Each intent recovery handler must transfer dfops here
> > - * before its local transaction commits, and we'll finish the entire
> > - * list below.
> > - */
> > - error = xfs_trans_alloc_empty(log->l_mp, &parent_tp);
> > - if (error)
> > - return error;
> > -
> > ailp = log->l_ailp;
> > spin_lock(&ailp->ail_lock);
> > - lip = xfs_trans_ail_cursor_first(ailp, &cur, 0);
> > #if defined(DEBUG) || defined(XFS_WARN)
> > last_lsn = xlog_assign_lsn(log->l_curr_cycle, log->l_curr_block);
> > #endif
> > - while (lip != NULL) {
> > + for (lip = xfs_trans_ail_cursor_first(ailp, &cur, 0);
> > + lip != NULL;
> > + lip = xfs_trans_ail_cursor_next(ailp, &cur)) {
> > /*
> > * We're done when we see something other than an intent.
> > * There should be no intents left in the AIL now.
> > @@ -2535,24 +2548,29 @@ xlog_recover_process_intents(
> >
> > /*
> > * NOTE: If your intent processing routine can create more
> > - * deferred ops, you /must/ attach them to the transaction in
> > - * this routine or else those subsequent intents will get
> > + * deferred ops, you /must/ attach them to the capture list in
> > + * the recover routine or else those subsequent intents will be
> > * replayed in the wrong order!
> > */
> > spin_unlock(&ailp->ail_lock);
> > - error = lip->li_ops->iop_recover(lip, parent_tp);
> > + error = lip->li_ops->iop_recover(lip, &capture_list);
> > spin_lock(&ailp->ail_lock);
> > if (error)
> > - goto out;
> > - lip = xfs_trans_ail_cursor_next(ailp, &cur);
> > + break;
> > }
> > -out:
> > +
> > xfs_trans_ail_cursor_done(&cur);
> > spin_unlock(&ailp->ail_lock);
> > - if (!error)
> > - error = xlog_finish_defer_ops(parent_tp);
> > - xfs_trans_cancel(parent_tp);
> > + if (error)
> > + goto err;
> >
> > + error = xlog_finish_defer_ops(log->l_mp, &capture_list);
> > + if (error)
> > + goto err;
> > +
> > + return 0;
> > +err:
> > + xlog_abort_defer_ops(log->l_mp, &capture_list);
> > return error;
> > }
> >
> > diff --git a/fs/xfs/xfs_refcount_item.c b/fs/xfs/xfs_refcount_item.c
> > index 3e34b7662361..0478374add64 100644
> > --- a/fs/xfs/xfs_refcount_item.c
> > +++ b/fs/xfs/xfs_refcount_item.c
> > @@ -424,7 +424,7 @@ const struct xfs_defer_op_type xfs_refcount_update_defer_type = {
> > STATIC int
> > xfs_cui_item_recover(
> > struct xfs_log_item *lip,
> > - struct xfs_trans *parent_tp)
> > + struct list_head *capture_list)
> > {
> > struct xfs_bmbt_irec irec;
> > struct xfs_cui_log_item *cuip = CUI_ITEM(lip);
> > @@ -432,7 +432,7 @@ xfs_cui_item_recover(
> > struct xfs_cud_log_item *cudp;
> > struct xfs_trans *tp;
> > struct xfs_btree_cur *rcur = NULL;
> > - struct xfs_mount *mp = parent_tp->t_mountp;
> > + struct xfs_mount *mp = lip->li_mountp;
> > xfs_fsblock_t startblock_fsb;
> > xfs_fsblock_t new_fsb;
> > xfs_extlen_t new_len;
> > @@ -487,12 +487,7 @@ xfs_cui_item_recover(
> > mp->m_refc_maxlevels * 2, 0, XFS_TRANS_RESERVE, &tp);
> > if (error)
> > return error;
> > - /*
> > - * Recovery stashes all deferred ops during intent processing and
> > - * finishes them on completion. Transfer current dfops state to this
> > - * transaction and transfer the result back before we return.
> > - */
> > - xfs_defer_move(tp, parent_tp);
> > +
> > cudp = xfs_trans_get_cud(tp, cuip);
> >
> > for (i = 0; i < cuip->cui_format.cui_nextents; i++) {
> > @@ -549,13 +544,10 @@ xfs_cui_item_recover(
> > }
> >
> > xfs_refcount_finish_one_cleanup(tp, rcur, error);
> > - xfs_defer_capture(parent_tp, tp);
> > - error = xfs_trans_commit(tp);
> > - return error;
> > + return xfs_defer_ops_capture_and_commit(tp, capture_list);
> >
> > abort_error:
> > xfs_refcount_finish_one_cleanup(tp, rcur, error);
> > - xfs_defer_move(parent_tp, tp);
> > xfs_trans_cancel(tp);
> > return error;
> > }
> > diff --git a/fs/xfs/xfs_rmap_item.c b/fs/xfs/xfs_rmap_item.c
> > index e38ec5d736be..0d8fa707f079 100644
> > --- a/fs/xfs/xfs_rmap_item.c
> > +++ b/fs/xfs/xfs_rmap_item.c
> > @@ -467,14 +467,14 @@ const struct xfs_defer_op_type xfs_rmap_update_defer_type = {
> > STATIC int
> > xfs_rui_item_recover(
> > struct xfs_log_item *lip,
> > - struct xfs_trans *parent_tp)
> > + struct list_head *capture_list)
> > {
> > struct xfs_rui_log_item *ruip = RUI_ITEM(lip);
> > struct xfs_map_extent *rmap;
> > struct xfs_rud_log_item *rudp;
> > struct xfs_trans *tp;
> > struct xfs_btree_cur *rcur = NULL;
> > - struct xfs_mount *mp = parent_tp->t_mountp;
> > + struct xfs_mount *mp = lip->li_mountp;
> > xfs_fsblock_t startblock_fsb;
> > enum xfs_rmap_intent_type type;
> > xfs_exntst_t state;
> > @@ -567,8 +567,7 @@ xfs_rui_item_recover(
> > }
> >
> > xfs_rmap_finish_one_cleanup(tp, rcur, error);
> > - error = xfs_trans_commit(tp);
> > - return error;
> > + return xfs_defer_ops_capture_and_commit(tp, capture_list);
> >
> > abort_error:
> > xfs_rmap_finish_one_cleanup(tp, rcur, error);
> > diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
> > index ced62a35a62b..186e77d08cc1 100644
> > --- a/fs/xfs/xfs_trans.h
> > +++ b/fs/xfs/xfs_trans.h
> > @@ -72,7 +72,8 @@ struct xfs_item_ops {
> > void (*iop_committing)(struct xfs_log_item *, xfs_lsn_t commit_lsn);
> > void (*iop_release)(struct xfs_log_item *);
> > xfs_lsn_t (*iop_committed)(struct xfs_log_item *, xfs_lsn_t);
> > - int (*iop_recover)(struct xfs_log_item *lip, struct xfs_trans *tp);
> > + int (*iop_recover)(struct xfs_log_item *lip,
> > + struct list_head *capture_list);
> > bool (*iop_match)(struct xfs_log_item *item, uint64_t id);
> > };
> >
> >
>
