On Wed, Oct 16, 2019 at 11:26:29AM -0400, Brian Foster wrote:
> On Wed, Oct 09, 2019 at 09:48:05AM -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 | 115 +++++++++++++++++++++++++++++++++++++++++++++
> > fs/xfs/libxfs/xfs_btree.h | 43 +++++++++++++++--
> > fs/xfs/xfs_trace.h | 28 +++++++++++
> > 3 files changed, 181 insertions(+), 5 deletions(-)
> >
> >
> > diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
> > index 71de937f9e64..7b18f0fa5e99 100644
> > --- a/fs/xfs/libxfs/xfs_btree.c
> > +++ b/fs/xfs/libxfs/xfs_btree.c
> ...
> > @@ -4930,3 +4932,116 @@ xfs_btree_has_more_records(
> ...
> > +/* Initialize a pointer to the root block from the fakeroot. */
> > +STATIC void
> > +xfs_btree_fakeroot_init_ptr_from_cur(
> > + struct xfs_btree_cur *cur,
> > + union xfs_btree_ptr *ptr)
> > +{
> > + struct xbtree_afakeroot *afake;
> > +
> > + ASSERT(cur->bc_flags & XFS_BTREE_STAGING);
> > +
> > + if (cur->bc_flags & XFS_BTREE_LONG_PTRS) {
> > + ptr->l = cpu_to_be64(0);
>
> Why zero here? Is this just not supported?
<shrug> The only existing longptr btree does this too.
There's no root block so we might as well set the pointer to 0 to catch
incorrect accesses.
> Otherwise this seems straightforward code-wise. I think I get the
> general idea, but it's hard to reason further about the pieces until I
> see the broader context..
Sorry about that. :/
You can skip to the v20 repair series to see how this all gets used in
the kernel, since the two sets in between are cleanups of other common
code. I also have a series to refactor xfs_repair to use btree bulk
loading[1], if that helps.
--D
[1] https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfsprogs-dev.git/log/?h=repair-bulk-load
> Brian
>
> > + } else {
> > + afake = cur->bc_private.a.afake;
> > + ptr->s = cpu_to_be32(afake->af_root);
> > + }
> > +}
> > +
> > +/* Set the root block when our tree has a fakeroot. */
> > +STATIC void
> > +xfs_btree_afakeroot_set_root(
> > + struct xfs_btree_cur *cur,
> > + union xfs_btree_ptr *ptr,
> > + int inc)
> > +{
> > + struct xbtree_afakeroot *afake = cur->bc_private.a.afake;
> > +
> > + ASSERT(cur->bc_flags & XFS_BTREE_STAGING);
> > + afake->af_root = be32_to_cpu(ptr->s);
> > + afake->af_levels += inc;
> > +}
> > +
> > +/*
> > + * Initialize a AG-rooted btree cursor with the given AG @fakeroot, and prepare
> > + * @ops for overriding by duplicating them into @new_ops. The caller can
> > + * replace pointers in @new_ops as necessary once this call completes. Note
> > + * that staging cursors can only be used for bulk loading.
> > + */
> > +void
> > +xfs_btree_stage_afakeroot(
> > + struct xfs_btree_cur *cur,
> > + struct xbtree_afakeroot *afake,
> > + const struct xfs_btree_ops *ops,
> > + struct xfs_btree_ops **new_ops)
> > +{
> > + ASSERT(!(cur->bc_flags & XFS_BTREE_STAGING));
> > + ASSERT(!(cur->bc_flags & XFS_BTREE_ROOT_IN_INODE));
> > +
> > + *new_ops = kmem_alloc(sizeof(struct xfs_btree_ops), KM_NOFS);
> > + memcpy(*new_ops, ops, sizeof(struct xfs_btree_ops));
> > + (*new_ops)->alloc_block = xfs_btree_fakeroot_alloc_block;
> > + (*new_ops)->free_block = xfs_btree_fakeroot_free_block;
> > + (*new_ops)->init_ptr_from_cur = xfs_btree_fakeroot_init_ptr_from_cur;
> > + (*new_ops)->set_root = xfs_btree_afakeroot_set_root;
> > + (*new_ops)->dup_cursor = xfs_btree_fakeroot_dup_cursor;
> > +
> > + cur->bc_private.a.afake = afake;
> > + cur->bc_nlevels = afake->af_levels;
> > + cur->bc_ops = *new_ops;
> > + cur->bc_flags |= XFS_BTREE_STAGING;
> > +}
> > +
> > +/*
> > + * Transform an AG-rooted staging btree cursor back into a regular btree
> > + * cursor. Caller is responsible for logging changes before this.
> > + */
> > +void
> > +xfs_btree_commit_afakeroot(
> > + struct xfs_btree_cur *cur,
> > + struct xfs_buf *agbp,
> > + const struct xfs_btree_ops *ops)
> > +{
> > + ASSERT(cur->bc_flags & XFS_BTREE_STAGING);
> > +
> > + trace_xfs_btree_commit_afakeroot(cur);
> > +
> > + kmem_free((void *)cur->bc_ops);
> > + cur->bc_private.a.agbp = agbp;
> > + cur->bc_ops = ops;
> > + cur->bc_flags &= ~XFS_BTREE_STAGING;
> > +}
> > diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h
> > index ced1e65d1483..453de8a49e96 100644
> > --- a/fs/xfs/libxfs/xfs_btree.h
> > +++ b/fs/xfs/libxfs/xfs_btree.h
> > @@ -185,6 +185,16 @@ union xfs_btree_cur_private {
> > } refc;
> > };
> >
> > +/* Private information for a AG-rooted btree. */
> > +struct xfs_btree_priv_ag { /* needed for BNO, CNT, INO */
> > + union {
> > + struct xfs_buf *agbp; /* agf/agi buffer pointer */
> > + struct xbtree_afakeroot *afake; /* fake ag header root */
> > + };
> > + xfs_agnumber_t agno; /* ag number */
> > + union xfs_btree_cur_private priv;
> > +};
> > +
> > /*
> > * Btree cursor structure.
> > * This collects all information needed by the btree code in one place.
> > @@ -206,11 +216,7 @@ typedef struct xfs_btree_cur
> > xfs_btnum_t bc_btnum; /* identifies which btree type */
> > int bc_statoff; /* offset of btre stats array */
> > union {
> > - struct { /* needed for BNO, CNT, INO */
> > - struct xfs_buf *agbp; /* agf/agi buffer pointer */
> > - xfs_agnumber_t agno; /* ag number */
> > - union xfs_btree_cur_private priv;
> > - } a;
> > + struct xfs_btree_priv_ag a;
> > struct { /* needed for BMAP */
> > struct xfs_inode *ip; /* pointer to our inode */
> > int allocated; /* count of alloced */
> > @@ -229,6 +235,12 @@ 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
> > @@ -514,4 +526,25 @@ int xfs_btree_has_record(struct xfs_btree_cur *cur, union xfs_btree_irec *low,
> > union xfs_btree_irec *high, bool *exists);
> > bool xfs_btree_has_more_records(struct xfs_btree_cur *cur);
> >
> > +/* 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,
> > + const struct xfs_btree_ops *ops,
> > + struct xfs_btree_ops **new_ops);
> > +void xfs_btree_commit_afakeroot(struct xfs_btree_cur *cur,
> > + 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 eaae275ed430..e04ed5324696 100644
> > --- a/fs/xfs/xfs_trace.h
> > +++ b/fs/xfs/xfs_trace.h
> > @@ -3609,6 +3609,34 @@ DEFINE_KMEM_EVENT(kmem_alloc_large);
> > DEFINE_KMEM_EVENT(kmem_realloc);
> > DEFINE_KMEM_EVENT(kmem_zone_alloc);
> >
> > +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_private.a.agno;
> > + __entry->agbno = cur->bc_private.a.afake->af_root;
> > + __entry->levels = cur->bc_private.a.afake->af_levels;
> > + __entry->blocks = cur->bc_private.a.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
> >
