Re: [PATCH 012/119] xfs: during btree split, save new block key & ptr for future insertion

Darrick J. Wong
2016-06-27T22:30:37Z

On Tue, Jun 21, 2016 at 09:00:45AM -0400, Brian Foster wrote:
> On Thu, Jun 16, 2016 at 06:19:08PM -0700, Darrick J. Wong wrote:
> > When a btree block has to be split, we pass the new block's ptr from
> > xfs_btree_split() back to xfs_btree_insert() via a pointer parameter;
> > however, we pass the block's key through the cursor's record. It is a
> > little weird to "initialize" a record from a key since the non-key
> > attributes will have garbage values.
> >
> > When we go to add support for interval queries, we have to be able to
> > pass the lowest and highest keys accessible via a pointer. There's no
> > clean way to pass this back through the cursor's record field.
> > Therefore, pass the key directly back to xfs_btree_insert() the same
> > way that we pass the btree_ptr.
> >
> > As a bonus, we no longer need init_rec_from_key and can drop it from the
> > codebase.
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> > fs/xfs/libxfs/xfs_alloc_btree.c | 12 ----------
> > fs/xfs/libxfs/xfs_bmap_btree.c | 12 ----------
> > fs/xfs/libxfs/xfs_btree.c | 44 +++++++++++++++++++-------------------
> > fs/xfs/libxfs/xfs_btree.h | 2 --
> > fs/xfs/libxfs/xfs_ialloc_btree.c | 10 ---------
> > 5 files changed, 22 insertions(+), 58 deletions(-)
> >
> >
> ...
> > diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
> > index 046fbcf..a096539 100644
> > --- a/fs/xfs/libxfs/xfs_btree.c
> > +++ b/fs/xfs/libxfs/xfs_btree.c
> ...
> > @@ -2929,16 +2927,16 @@ xfs_btree_insrec(
> > struct xfs_btree_cur *cur, /* btree cursor */
> > int level, /* level to insert record at */
> > union xfs_btree_ptr *ptrp, /* i/o: block number inserted */
> > - union xfs_btree_rec *recp, /* i/o: record data inserted */
> > + union xfs_btree_key *key, /* i/o: block key for ptrp */
> > struct xfs_btree_cur **curp, /* output: new cursor replacing cur */
> > int *stat) /* success/failure */
> > {
> > struct xfs_btree_block *block; /* btree block */
> > struct xfs_buf *bp; /* buffer for block */
> > - union xfs_btree_key key; /* btree key */
> > union xfs_btree_ptr nptr; /* new block ptr */
> > struct xfs_btree_cur *ncur; /* new btree cursor */
> > - union xfs_btree_rec nrec; /* new record count */
> > + union xfs_btree_key nkey; /* new block key */
> > + union xfs_btree_rec rec; /* record to insert */
> > int optr; /* old key/record index */
> > int ptr; /* key/record index */
> > int numrecs;/* number of records */
> > @@ -2947,8 +2945,14 @@ xfs_btree_insrec(
> > int i;
> > #endif
> >
> > + /* Make a key out of the record data to be inserted, and save it. */
> > + if (level == 0) {
> > + cur->bc_ops->init_rec_from_cur(cur, &rec);
> > + cur->bc_ops->init_key_from_rec(key, &rec);
> > + }
>
> The level == 0 check looks a bit hacky to me. IOW, I think it's cleaner
> that the key is initialized once in the caller rather than check for a
> particular iteration down in xfs_btree_insrec(). That said,
> xfs_btree_insrec() still needs rec initialized in the level == 0 case.
>
> I wonder if we could create an inline xfs_btree_init_key_from_cur()
> helper to combine the above calls, invoke it once in xfs_btree_insert(),
> then push down the ->init_rec_from_cur() calls to the contexts further
> down in this function where rec is actually required. There are only two
> and one of them is DEBUG code. Thoughts?

How about I make btree_insert set both &key and &rec at the start and
pass them both into btree_insrec? That would eliminate the hacky check
above and fix the dummy tracing hook too, in case it ever does anything.

>
> > +
> > XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
> > - XFS_BTREE_TRACE_ARGIPR(cur, level, *ptrp, recp);
> > + XFS_BTREE_TRACE_ARGIPR(cur, level, *ptrp, &rec);
> >
>
> So these look like unimplemented dummy tracing hooks. It sounds like
> previously rec could have a junk value after a btree split, but now it
> looks like rec is junk for every non-zero level. Kind of annoying, I
> wonder if we can just kill these.. :/

<shrug> I have no opinion either way. :)

--D
>
> Brian
>
> > ncur = NULL;
> >
> > @@ -2973,9 +2977,6 @@ xfs_btree_insrec(
> > return 0;
> > }
> >
> > - /* Make a key out of the record data to be inserted, and save it. */
> > - cur->bc_ops->init_key_from_rec(&key, recp);
> > -
> > optr = ptr;
> >
> > XFS_BTREE_STATS_INC(cur, insrec);
> > @@ -2992,10 +2993,10 @@ xfs_btree_insrec(
> > /* Check that the new entry is being inserted in the right place. */
> > if (ptr <= numrecs) {
> > if (level == 0) {
> > - ASSERT(cur->bc_ops->recs_inorder(cur, recp,
> > + ASSERT(cur->bc_ops->recs_inorder(cur, &rec,
> > xfs_btree_rec_addr(cur, ptr, block)));
> > } else {
> > - ASSERT(cur->bc_ops->keys_inorder(cur, &key,
> > + ASSERT(cur->bc_ops->keys_inorder(cur, key,
> > xfs_btree_key_addr(cur, ptr, block)));
> > }
> > }
> > @@ -3008,7 +3009,7 @@ xfs_btree_insrec(
> > xfs_btree_set_ptr_null(cur, &nptr);
> > if (numrecs == cur->bc_ops->get_maxrecs(cur, level)) {
> > error = xfs_btree_make_block_unfull(cur, level, numrecs,
> > - &optr, &ptr, &nptr, &ncur, &nrec, stat);
> > + &optr, &ptr, &nptr, &ncur, &nkey, stat);
> > if (error || *stat == 0)
> > goto error0;
> > }
> > @@ -3058,7 +3059,7 @@ xfs_btree_insrec(
> > #endif
> >
> > /* Now put the new data in, bump numrecs and log it. */
> > - xfs_btree_copy_keys(cur, kp, &key, 1);
> > + xfs_btree_copy_keys(cur, kp, key, 1);
> > xfs_btree_copy_ptrs(cur, pp, ptrp, 1);
> > numrecs++;
> > xfs_btree_set_numrecs(block, numrecs);
> > @@ -3079,7 +3080,7 @@ xfs_btree_insrec(
> > xfs_btree_shift_recs(cur, rp, 1, numrecs - ptr + 1);
> >
> > /* Now put the new data in, bump numrecs and log it. */
> > - xfs_btree_copy_recs(cur, rp, recp, 1);
> > + xfs_btree_copy_recs(cur, rp, &rec, 1);
> > xfs_btree_set_numrecs(block, ++numrecs);
> > xfs_btree_log_recs(cur, bp, ptr, numrecs);
> > #ifdef DEBUG
> > @@ -3095,7 +3096,7 @@ xfs_btree_insrec(
> >
> > /* If we inserted at the start of a block, update the parents' keys. */
> > if (optr == 1) {
> > - error = xfs_btree_updkey(cur, &key, level + 1);
> > + error = xfs_btree_updkey(cur, key, level + 1);
> > if (error)
> > goto error0;
> > }
> > @@ -3105,7 +3106,7 @@ xfs_btree_insrec(
> > * we are at the far right edge of the tree, update it.
> > */
> > if (xfs_btree_is_lastrec(cur, block, level)) {
> > - cur->bc_ops->update_lastrec(cur, block, recp,
> > + cur->bc_ops->update_lastrec(cur, block, &rec,
> > ptr, LASTREC_INSREC);
> > }
> >
> > @@ -3115,7 +3116,7 @@ xfs_btree_insrec(
> > */
> > *ptrp = nptr;
> > if (!xfs_btree_ptr_is_null(cur, &nptr)) {
> > - *recp = nrec;
> > + *key = nkey;
> > *curp = ncur;
> > }
> >
> > @@ -3146,14 +3147,13 @@ xfs_btree_insert(
> > union xfs_btree_ptr nptr; /* new block number (split result) */
> > struct xfs_btree_cur *ncur; /* new cursor (split result) */
> > struct xfs_btree_cur *pcur; /* previous level's cursor */
> > - union xfs_btree_rec rec; /* record to insert */
> > + union xfs_btree_key key; /* key of block to insert */
> >
> > level = 0;
> > ncur = NULL;
> > pcur = cur;
> >
> > xfs_btree_set_ptr_null(cur, &nptr);
> > - cur->bc_ops->init_rec_from_cur(cur, &rec);
> >
> > /*
> > * Loop going up the tree, starting at the leaf level.
> > @@ -3165,7 +3165,7 @@ xfs_btree_insert(
> > * Insert nrec/nptr into this level of the tree.
> > * Note if we fail, nptr will be null.
> > */
> > - error = xfs_btree_insrec(pcur, level, &nptr, &rec, &ncur, &i);
> > + error = xfs_btree_insrec(pcur, level, &nptr, &key, &ncur, &i);
> > if (error) {
> > if (pcur != cur)
> > xfs_btree_del_cursor(pcur, XFS_BTREE_ERROR);
> > diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h
> > index b955e5d..b99c018 100644
> > --- a/fs/xfs/libxfs/xfs_btree.h
> > +++ b/fs/xfs/libxfs/xfs_btree.h
> > @@ -158,8 +158,6 @@ struct xfs_btree_ops {
> > /* init values of btree structures */
> > void (*init_key_from_rec)(union xfs_btree_key *key,
> > union xfs_btree_rec *rec);
> > - void (*init_rec_from_key)(union xfs_btree_key *key,
> > - union xfs_btree_rec *rec);
> > void (*init_rec_from_cur)(struct xfs_btree_cur *cur,
> > union xfs_btree_rec *rec);
> > void (*init_ptr_from_cur)(struct xfs_btree_cur *cur,
> > diff --git a/fs/xfs/libxfs/xfs_ialloc_btree.c b/fs/xfs/libxfs/xfs_ialloc_btree.c
> > index 89c21d7..88da2ad 100644
> > --- a/fs/xfs/libxfs/xfs_ialloc_btree.c
> > +++ b/fs/xfs/libxfs/xfs_ialloc_btree.c
> > @@ -146,14 +146,6 @@ xfs_inobt_init_key_from_rec(
> > }
> >
> > STATIC void
> > -xfs_inobt_init_rec_from_key(
> > - union xfs_btree_key *key,
> > - union xfs_btree_rec *rec)
> > -{
> > - rec->inobt.ir_startino = key->inobt.ir_startino;
> > -}
> > -
> > -STATIC void
> > xfs_inobt_init_rec_from_cur(
> > struct xfs_btree_cur *cur,
> > union xfs_btree_rec *rec)
> > @@ -314,7 +306,6 @@ static const struct xfs_btree_ops xfs_inobt_ops = {
> > .get_minrecs = xfs_inobt_get_minrecs,
> > .get_maxrecs = xfs_inobt_get_maxrecs,
> > .init_key_from_rec = xfs_inobt_init_key_from_rec,
> > - .init_rec_from_key = xfs_inobt_init_rec_from_key,
> > .init_rec_from_cur = xfs_inobt_init_rec_from_cur,
> > .init_ptr_from_cur = xfs_inobt_init_ptr_from_cur,
> > .key_diff = xfs_inobt_key_diff,
> > @@ -336,7 +327,6 @@ static const struct xfs_btree_ops xfs_finobt_ops = {
> > .get_minrecs = xfs_inobt_get_minrecs,
> > .get_maxrecs = xfs_inobt_get_maxrecs,
> > .init_key_from_rec = xfs_inobt_init_key_from_rec,
> > - .init_rec_from_key = xfs_inobt_init_rec_from_key,
> > .init_rec_from_cur = xfs_inobt_init_rec_from_cur,
> > .init_ptr_from_cur = xfs_finobt_init_ptr_from_cur,
> > .key_diff = xfs_inobt_key_diff,
> >
> > _______________________________________________
> > xfs mailing list
> > xfs@oss.sgi.com
> > http://oss.sgi.com/mailman/listinfo/xfs