xfs: introduce fake roots for inode-rooted btrees

Create an in-core fake root for inode-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@oracle.com>

3 files changed, 154 insertions, 13 deletions

diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
index 24fd8357a39c..851590f2b16e 100644
--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -646,6 +646,17 @@ xfs_btree_ptr_addr(
 		((char *)block + xfs_btree_ptr_offset(cur, n, level));
 }
 
+struct xfs_ifork *
+xfs_btree_ifork_ptr(
+	struct xfs_btree_cur	*cur)
+{
+	ASSERT(cur->bc_flags & XFS_BTREE_ROOT_IN_INODE);
+
+	if (cur->bc_flags & XFS_BTREE_STAGING)
+		return cur->bc_private.b.ifake->if_fork;
+	return XFS_IFORK_PTR(cur->bc_private.b.ip, cur->bc_private.b.whichfork);
+}
+
 /*
  * Get the root block which is stored in the inode.
  *
@@ -656,9 +667,8 @@ STATIC struct xfs_btree_block *
 xfs_btree_get_iroot(
 	struct xfs_btree_cur	*cur)
 {
-	struct xfs_ifork	*ifp;
+	struct xfs_ifork	*ifp = xfs_btree_ifork_ptr(cur);
 
-	ifp = XFS_IFORK_PTR(cur->bc_private.b.ip, cur->bc_private.b.whichfork);
 	return (struct xfs_btree_block *)ifp->if_broot;
 }
 
@@ -4980,8 +4990,17 @@ xfs_btree_fakeroot_init_ptr_from_cur(
 
 	ASSERT(cur->bc_flags & XFS_BTREE_STAGING);
 
-	afake = cur->bc_private.a.afake;
-	ptr->s = cpu_to_be32(afake->af_root);
+	if (cur->bc_flags & XFS_BTREE_ROOT_IN_INODE) {
+		/*
+		 * The root block lives in the inode core, so we zero the
+		 * pointer (like the bmbt code does) to make it obvious if
+		 * anyone ever tries to use this pointer.
+		 */
+		ptr->l = cpu_to_be64(0);
+	} 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. */
@@ -5053,3 +5072,58 @@ xfs_btree_commit_afakeroot(
 	cur->bc_ops = ops;
 	cur->bc_flags &= ~XFS_BTREE_STAGING;
 }
+/*
+ * Initialize an inode-rooted btree cursor with the given inode 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_ifakeroot(
+	struct xfs_btree_cur		*cur,
+	struct xbtree_ifakeroot		*ifake,
+	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);
+
+	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->dup_cursor = xfs_btree_fakeroot_dup_cursor;
+
+	cur->bc_private.b.ifake = ifake;
+	cur->bc_nlevels = ifake->if_levels;
+	cur->bc_ops = nops;
+	cur->bc_flags |= XFS_BTREE_STAGING;
+
+	if (new_ops)
+		*new_ops = nops;
+}
+
+/*
+ * Transform an inode-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_ifakeroot(
+	struct xfs_btree_cur		*cur,
+	int				whichfork,
+	const struct xfs_btree_ops	*ops)
+{
+	ASSERT(cur->bc_flags & XFS_BTREE_STAGING);
+
+	trace_xfs_btree_commit_ifakeroot(cur);
+
+	kmem_free((void *)cur->bc_ops);
+	cur->bc_private.b.ifake = NULL;
+	cur->bc_private.b.whichfork = whichfork;
+	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 39ca3f0a3bf8..d1df48d3d1ee 100644
--- a/fs/xfs/libxfs/xfs_btree.h
+++ b/fs/xfs/libxfs/xfs_btree.h
@@ -10,6 +10,7 @@ struct xfs_buf;
 struct xfs_inode;
 struct xfs_mount;
 struct xfs_trans;
+struct xfs_ifork;
 
 extern kmem_zone_t	*xfs_btree_cur_zone;
 
@@ -195,6 +196,18 @@ struct xfs_btree_priv_ag {			/* needed for BNO, CNT, INO */
 	union xfs_btree_cur_private	priv;
 };
 
+/* Private information for an inode-rooted btree. */
+struct xfs_btree_priv_inode {			/* needed for BMAP */
+	struct xfs_inode	*ip;		/* pointer to our inode */
+	struct xbtree_ifakeroot	*ifake;		/* fake inode fork */
+	int			allocated;	/* count of alloced */
+	short			forksize;	/* fork's inode space */
+	char			whichfork;	/* data or attr fork */
+	char			flags;		/* flags */
+#define	XFS_BTCUR_BPRV_WASDEL		(1<<0)	/* was delayed */
+#define	XFS_BTCUR_BPRV_INVALID_OWNER	(1<<1)	/* for ext swap */
+};
+
 /*
  * Btree cursor structure.
  * This collects all information needed by the btree code in one place.
@@ -217,15 +230,7 @@ typedef struct xfs_btree_cur
 	int		bc_statoff;	/* offset of btre stats array */
 	union {
 		struct xfs_btree_priv_ag a;
-		struct {			/* needed for BMAP */
-			struct xfs_inode *ip;	/* pointer to our inode */
-			int		allocated;	/* count of alloced */
-			short		forksize;	/* fork's inode space */
-			char		whichfork;	/* data or attr fork */
-			char		flags;		/* flags */
-#define	XFS_BTCUR_BPRV_WASDEL		(1<<0)		/* was delayed */
-#define	XFS_BTCUR_BPRV_INVALID_OWNER	(1<<1)		/* for ext swap */
-		} b;
+		struct xfs_btree_priv_inode b;
 	}		bc_private;	/* per-btree type data */
 } xfs_btree_cur_t;
 
@@ -532,6 +537,7 @@ union xfs_btree_key *xfs_btree_high_key_from_key(struct xfs_btree_cur *cur,
 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);
+struct xfs_ifork *xfs_btree_ifork_ptr(struct xfs_btree_cur *cur);
 
 /* Fake root for an AG-rooted btree. */
 struct xbtree_afakeroot {
@@ -553,4 +559,32 @@ void xfs_btree_commit_afakeroot(struct xfs_btree_cur *cur,
 		struct xfs_buf *agbp,
 		const struct xfs_btree_ops *ops);
 
+/* Fake root for an inode-rooted btree. */
+struct xbtree_ifakeroot {
+	/* Fake inode fork. */
+	struct xfs_ifork	*if_fork;
+
+	/* Number of blocks used by the btree. */
+	int64_t			if_blocks;
+
+	/* Height of the new btree. */
+	unsigned int		if_levels;
+
+	/* Number of bytes available for this fork in the inode. */
+	unsigned int		if_fork_size;
+
+	/* Fork format. */
+	unsigned int		if_format;
+
+	/* Number of records. */
+	unsigned int		if_extents;
+};
+
+/* Cursor interactions with with fake roots for inode-rooted btrees. */
+void xfs_btree_stage_ifakeroot(struct xfs_btree_cur *cur,
+		struct xbtree_ifakeroot *ifake,
+		struct xfs_btree_ops **new_ops);
+void xfs_btree_commit_ifakeroot(struct xfs_btree_cur *cur, int whichfork,
+		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 e04ed5324696..a78055521fcd 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -3637,6 +3637,39 @@ TRACE_EVENT(xfs_btree_commit_afakeroot,
 		  __entry->agbno)
 )
 
+TRACE_EVENT(xfs_btree_commit_ifakeroot,
+	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_agino_t, agino)
+		__field(unsigned int, levels)
+		__field(unsigned int, blocks)
+		__field(int, whichfork)
+	),
+	TP_fast_assign(
+		__entry->dev = cur->bc_mp->m_super->s_dev;
+		__entry->btnum = cur->bc_btnum;
+		__entry->agno = XFS_INO_TO_AGNO(cur->bc_mp,
+					cur->bc_private.b.ip->i_ino);
+		__entry->agino = XFS_INO_TO_AGINO(cur->bc_mp,
+					cur->bc_private.b.ip->i_ino);
+		__entry->levels = cur->bc_private.b.ifake->if_levels;
+		__entry->blocks = cur->bc_private.b.ifake->if_blocks;
+		__entry->whichfork = cur->bc_private.b.whichfork;
+	),
+	TP_printk("dev %d:%d btree %s ag %u agino %u whichfork %s levels %u blocks %u",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __print_symbolic(__entry->btnum, XFS_BTNUM_STRINGS),
+		  __entry->agno,
+		  __entry->agino,
+		  __entry->whichfork == XFS_ATTR_FORK ? "attr" : "data",
+		  __entry->levels,
+		  __entry->blocks)
+)
+
 #endif /* _TRACE_XFS_H */
 
 #undef TRACE_INCLUDE_PATH