[Linux-cachefs] [PATCH v11 3/4] xfs: refactor the usage around xfs_trans_context_{set, clear}

[Yafang Shao]

On Wed, Dec 9, 2020 at 2:59 AM Darrick J. Wong <darrick.wong at oracle.com> wrote:
>
> On Tue, Dec 08, 2020 at 08:28:23PM +0800, Yafang Shao wrote:
> > The xfs_trans context should be active after it is allocated, and
> > deactive when it is freed.
> >
> > So these two helpers are refactored as,
> > - xfs_trans_context_set()
> >   Used in xfs_trans_alloc()
> > - xfs_trans_context_clear()
> >   Used in xfs_trans_free()
> >
> > This patch is based on Darrick's work to fix the issue in xfs/141 in the
> > earlier version. [1]
> >
> > 1. https://lore.kernel.org/linux-xfs/20201104001649.GN7123@magnolia
> >
> > Cc: Darrick J. Wong <darrick.wong at oracle.com>
> > Cc: Matthew Wilcox (Oracle) <willy at infradead.org>
> > Cc: Christoph Hellwig <hch at lst.de>
> > Cc: Dave Chinner <david at fromorbit.com>
> > Signed-off-by: Yafang Shao <laoar.shao at gmail.com>
> > ---
> >  fs/xfs/xfs_trans.c | 20 +++++++-------------
> >  1 file changed, 7 insertions(+), 13 deletions(-)
> >
> > diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
> > index 11d390f0d3f2..fe20398a214e 100644
> > --- a/fs/xfs/xfs_trans.c
> > +++ b/fs/xfs/xfs_trans.c
> > @@ -67,6 +67,9 @@ xfs_trans_free(
> >       xfs_extent_busy_sort(&tp->t_busy);
> >       xfs_extent_busy_clear(tp->t_mountp, &tp->t_busy, false);
> >
> > +     /* Detach the transaction from this thread. */
> > +     xfs_trans_context_clear(tp);
>
> Don't you need to check if tp is still the current transaction before
> you clear PF_MEMALLOC_NOFS, now that the NOFS is bound to the lifespan
> of the transaction itself instead of the reservation?
>

The current->journal_info is always the same with tp here in my verification.
I don't know in which case they are different. It would be better if
you could explain in detail.
Anyway I can add the check with your comment in the next version.


>
> > +
> >       trace_xfs_trans_free(tp, _RET_IP_);
> >       if (!(tp->t_flags & XFS_TRANS_NO_WRITECOUNT))
> >               sb_end_intwrite(tp->t_mountp->m_super);
> > @@ -153,9 +156,6 @@ xfs_trans_reserve(
> >       int                     error = 0;
> >       bool                    rsvd = (tp->t_flags & XFS_TRANS_RESERVE) != 0;
> >
> > -     /* Mark this thread as being in a transaction */
> > -     xfs_trans_context_set(tp);
> > -
> >       /*
> >        * Attempt to reserve the needed disk blocks by decrementing
> >        * the number needed from the number available.  This will
> > @@ -163,10 +163,9 @@ xfs_trans_reserve(
> >        */
> >       if (blocks > 0) {
> >               error = xfs_mod_fdblocks(mp, -((int64_t)blocks), rsvd);
> > -             if (error != 0) {
> > -                     xfs_trans_context_clear(tp);
> > +             if (error != 0)
> >                       return -ENOSPC;
> > -             }
> > +
> >               tp->t_blk_res += blocks;
> >       }
> >
> > @@ -241,8 +240,6 @@ xfs_trans_reserve(
> >               tp->t_blk_res = 0;
> >       }
> >
> > -     xfs_trans_context_clear(tp);
> > -
> >       return error;
> >  }
> >
> > @@ -284,6 +281,8 @@ xfs_trans_alloc(
> >       INIT_LIST_HEAD(&tp->t_dfops);
> >       tp->t_firstblock = NULLFSBLOCK;
> >
> > +     /* Mark this thread as being in a transaction */
> > +     xfs_trans_context_set(tp);
> >       error = xfs_trans_reserve(tp, resp, blocks, rtextents);
> >       if (error) {
> >               xfs_trans_cancel(tp);
> > @@ -878,7 +877,6 @@ __xfs_trans_commit(
> >
> >       xfs_log_commit_cil(mp, tp, &commit_lsn, regrant);
> >
> > -     xfs_trans_context_clear(tp);
> >       xfs_trans_free(tp);
> >
> >       /*
> > @@ -911,7 +909,6 @@ __xfs_trans_commit(
> >               tp->t_ticket = NULL;
> >       }
> >
> > -     xfs_trans_context_clear(tp);
> >       xfs_trans_free_items(tp, !!error);
> >       xfs_trans_free(tp);
> >
> > @@ -971,9 +968,6 @@ xfs_trans_cancel(
> >               tp->t_ticket = NULL;
> >       }
> >
> > -     /* mark this thread as no longer being in a transaction */
> > -     xfs_trans_context_clear(tp);
> > -
> >       xfs_trans_free_items(tp, dirty);
> >       xfs_trans_free(tp);
> >  }
> > --
> > 2.18.4
> >



-- 
Thanks
Yafang