On Fri, Mar 13, 2020 at 10:47:12AM -0400, Brian Foster wrote:
> On Wed, Mar 11, 2020 at 08:45:37PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> >
> > Create an in-core fake root for AG-rooted btree types so that callers
> > can generate a whole new btree using the upcoming btree bulk load
> > function without making the new tree accessible from the rest of the
> > filesystem. It is up to the individual btree type to provide a function
> > to create a staged cursor (presumably with the appropriate callouts to
> > update the fakeroot) and then commit the staged root back into the
> > filesystem.
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > ---
> > fs/xfs/libxfs/xfs_btree.c | 168 +++++++++++++++++++++++++++++++++++++++++++++
> > fs/xfs/libxfs/xfs_btree.h | 30 ++++++++
> > fs/xfs/xfs_trace.h | 28 ++++++++
> > 3 files changed, 225 insertions(+), 1 deletion(-)
> >
> >
> > diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
> > index 4ef9f0b42c7f..085bc070e804 100644
> > --- a/fs/xfs/libxfs/xfs_btree.c
> > +++ b/fs/xfs/libxfs/xfs_btree.c
> ...
> > @@ -4908,3 +4910,169 @@ xfs_btree_has_more_records(
> > else
> > return block->bb_u.s.bb_rightsib != cpu_to_be32(NULLAGBLOCK);
> > }
> > +
> ...
> > +/*
> > + * Initialize a AG-rooted btree cursor with the given AG btree fake root. The
> > + * btree cursor's bc_ops will be overridden as needed to make the staging
> > + * functionality work. If new_ops is not NULL, these new ops will be passed
> > + * out to the caller for further overriding.
> > + */
> > +void
> > +xfs_btree_stage_afakeroot(
> > + struct xfs_btree_cur *cur,
> > + struct xbtree_afakeroot *afake,
> > + struct xfs_btree_ops **new_ops)
> > +{
> > + struct xfs_btree_ops *nops;
> > +
> > + ASSERT(!(cur->bc_flags & XFS_BTREE_STAGING));
> > + ASSERT(!(cur->bc_flags & XFS_BTREE_ROOT_IN_INODE));
> > + ASSERT(cur->bc_tp == NULL);
> > +
> > + nops = kmem_alloc(sizeof(struct xfs_btree_ops), KM_NOFS);
> > + memcpy(nops, cur->bc_ops, sizeof(struct xfs_btree_ops));
> > + nops->alloc_block = xfs_btree_fakeroot_alloc_block;
> > + nops->free_block = xfs_btree_fakeroot_free_block;
> > + nops->init_ptr_from_cur = xfs_btree_fakeroot_init_ptr_from_cur;
> > + nops->set_root = xfs_btree_afakeroot_set_root;
> > + nops->dup_cursor = xfs_btree_fakeroot_dup_cursor;
> > +
> > + cur->bc_ag.afake = afake;
> > + cur->bc_nlevels = afake->af_levels;
> > + cur->bc_ops = nops;
> > + cur->bc_flags |= XFS_BTREE_STAGING;
> > +
> > + if (new_ops)
> > + *new_ops = nops;
>
> Curious why we have new_ops if the caller unconditionally assigns
> ->bc_ops to the same value..? That aside:
The callers don't assign bc_ops anymore, though the benefit of hindsight
is that nobody uses *new_ops here so perhaps it makes more sense to drop
the parameter for _afakeroot.
--D
> Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
>
> > +}
> > +
> > +/*
> > + * Transform an AG-rooted staging btree cursor back into a regular cursor by
> > + * substituting a real btree root for the fake one and restoring normal btree
> > + * cursor ops. The caller must log the btree root change prior to calling
> > + * this.
> > + */
> > +void
> > +xfs_btree_commit_afakeroot(
> > + struct xfs_btree_cur *cur,
> > + struct xfs_trans *tp,
> > + struct xfs_buf *agbp,
> > + const struct xfs_btree_ops *ops)
> > +{
> > + ASSERT(cur->bc_flags & XFS_BTREE_STAGING);
> > + ASSERT(cur->bc_tp == NULL);
> > +
> > + trace_xfs_btree_commit_afakeroot(cur);
> > +
> > + kmem_free((void *)cur->bc_ops);
> > + cur->bc_ag.agbp = agbp;
> > + cur->bc_ops = ops;
> > + cur->bc_flags &= ~XFS_BTREE_STAGING;
> > + cur->bc_tp = tp;
> > +}
> > diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h
> > index 0d10bbd5223a..aa4a7bd40023 100644
> > --- a/fs/xfs/libxfs/xfs_btree.h
> > +++ b/fs/xfs/libxfs/xfs_btree.h
> > @@ -179,7 +179,10 @@ union xfs_btree_irec {
> >
> > /* Per-AG btree information. */
> > struct xfs_btree_cur_ag {
> > - struct xfs_buf *agbp;
> > + union {
> > + struct xfs_buf *agbp;
> > + struct xbtree_afakeroot *afake; /* fake ag header root */
> > + };
> > xfs_agnumber_t agno;
> > union {
> > struct {
> > @@ -235,6 +238,12 @@ typedef struct xfs_btree_cur
> > #define XFS_BTREE_LASTREC_UPDATE (1<<2) /* track last rec externally */
> > #define XFS_BTREE_CRC_BLOCKS (1<<3) /* uses extended btree blocks */
> > #define XFS_BTREE_OVERLAPPING (1<<4) /* overlapping intervals */
> > +/*
> > + * The root of this btree is a fakeroot structure so that we can stage a btree
> > + * rebuild without leaving it accessible via primary metadata. The ops struct
> > + * is dynamically allocated and must be freed when the cursor is deleted.
> > + */
> > +#define XFS_BTREE_STAGING (1<<5)
> >
> >
> > #define XFS_BTREE_NOERROR 0
> > @@ -515,4 +524,23 @@ xfs_btree_islastblock(
> > return block->bb_u.s.bb_rightsib == cpu_to_be32(NULLAGBLOCK);
> > }
> >
> > +/* Fake root for an AG-rooted btree. */
> > +struct xbtree_afakeroot {
> > + /* AG block number of the new btree root. */
> > + xfs_agblock_t af_root;
> > +
> > + /* Height of the new btree. */
> > + unsigned int af_levels;
> > +
> > + /* Number of blocks used by the btree. */
> > + unsigned int af_blocks;
> > +};
> > +
> > +/* Cursor interactions with with fake roots for AG-rooted btrees. */
> > +void xfs_btree_stage_afakeroot(struct xfs_btree_cur *cur,
> > + struct xbtree_afakeroot *afake,
> > + struct xfs_btree_ops **new_ops);
> > +void xfs_btree_commit_afakeroot(struct xfs_btree_cur *cur, struct xfs_trans *tp,
> > + struct xfs_buf *agbp, const struct xfs_btree_ops *ops);
> > +
> > #endif /* __XFS_BTREE_H__ */
> > diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
> > index 059c3098a4a0..d8c229492973 100644
> > --- a/fs/xfs/xfs_trace.h
> > +++ b/fs/xfs/xfs_trace.h
> > @@ -3605,6 +3605,34 @@ TRACE_EVENT(xfs_check_new_dalign,
> > __entry->calc_rootino)
> > )
> >
> > +TRACE_EVENT(xfs_btree_commit_afakeroot,
> > + TP_PROTO(struct xfs_btree_cur *cur),
> > + TP_ARGS(cur),
> > + TP_STRUCT__entry(
> > + __field(dev_t, dev)
> > + __field(xfs_btnum_t, btnum)
> > + __field(xfs_agnumber_t, agno)
> > + __field(xfs_agblock_t, agbno)
> > + __field(unsigned int, levels)
> > + __field(unsigned int, blocks)
> > + ),
> > + TP_fast_assign(
> > + __entry->dev = cur->bc_mp->m_super->s_dev;
> > + __entry->btnum = cur->bc_btnum;
> > + __entry->agno = cur->bc_ag.agno;
> > + __entry->agbno = cur->bc_ag.afake->af_root;
> > + __entry->levels = cur->bc_ag.afake->af_levels;
> > + __entry->blocks = cur->bc_ag.afake->af_blocks;
> > + ),
> > + TP_printk("dev %d:%d btree %s ag %u levels %u blocks %u root %u",
> > + MAJOR(__entry->dev), MINOR(__entry->dev),
> > + __print_symbolic(__entry->btnum, XFS_BTNUM_STRINGS),
> > + __entry->agno,
> > + __entry->levels,
> > + __entry->blocks,
> > + __entry->agbno)
> > +)
> > +
> > #endif /* _TRACE_XFS_H */
> >
> > #undef TRACE_INCLUDE_PATH
> >
>
