xfs: remove xfs_btree_cur private firstblock field

The bmbt cursor private structure has a firstblock field that is
used to maintain locking order on bmbt allocations. The field holds
an actual firstblock value (as opposed to a pointer), so it is
initialized on cursor creation, updated on allocation and then the
value is transferred back to the source before the cursor is
destroyed.

This value is always transferred from and back to the ->t_firstblock
field. Since xfs_btree_cur already carries a reference to the
transaction, we can remove this field from xfs_btree_cur and the
associated copying. The bmbt allocations will update the value in
the transaction directly.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/libxfs/xfs_bmap.c

@@ -688,7 +688,6 @@ xfs_bmap_extents_to_btree(
 	 * Need a cursor.  Can't allocate until bb_level is filled in.
 	 */
 	cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
-	cur->bc_private.b.firstblock = tp->t_firstblock;
 	cur->bc_private.b.flags = wasdel ? XFS_BTCUR_BPRV_WASDEL : 0;
 	/*
 	 * Convert to a btree with two levels, one record in root.
@@ -732,7 +731,7 @@ xfs_bmap_extents_to_btree(
 	 */
 	ASSERT(tp->t_firstblock == NULLFSBLOCK ||
 	       args.agno >= XFS_FSB_TO_AGNO(mp, tp->t_firstblock));
-	tp->t_firstblock = cur->bc_private.b.firstblock = args.fsbno;
+	tp->t_firstblock = args.fsbno;
 	cur->bc_private.b.allocated++;
 	ip->i_d.di_nblocks++;
 	xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_BCOUNT, 1L);
@@ -925,7 +924,6 @@ xfs_bmap_add_attrfork_btree(
 		*flags |= XFS_ILOG_DBROOT;
 	else {
 		cur = xfs_bmbt_init_cursor(mp, tp, ip, XFS_DATA_FORK);
-		cur->bc_private.b.firstblock = tp->t_firstblock;
 		error = xfs_bmbt_lookup_first(cur, &stat);
 		if (error)
 			goto error0;
@@ -937,7 +935,6 @@ xfs_bmap_add_attrfork_btree(
 			xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
 			return -ENOSPC;
 		}
-		tp->t_firstblock = cur->bc_private.b.firstblock;
 		cur->bc_private.b.allocated = 0;
 		xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
 	}
@@ -4058,14 +4055,10 @@ xfs_bmapi_allocate(
 	if (error)
 		return error;
 
-	if (bma->cur)
-		bma->cur->bc_private.b.firstblock = bma->tp->t_firstblock;
 	if (bma->blkno == NULLFSBLOCK)
 		return 0;
-	if ((ifp->if_flags & XFS_IFBROOT) && !bma->cur) {
+	if ((ifp->if_flags & XFS_IFBROOT) && !bma->cur)
 		bma->cur = xfs_bmbt_init_cursor(mp, bma->tp, bma->ip, whichfork);
-		bma->cur->bc_private.b.firstblock = bma->tp->t_firstblock;
-	}
 	/*
 	 * Bump the number of extents we've allocated
 	 * in this call.
@@ -4151,7 +4144,6 @@ xfs_bmapi_convert_unwritten(
 	if ((ifp->if_flags & XFS_IFBROOT) && !bma->cur) {
 		bma->cur = xfs_bmbt_init_cursor(bma->ip->i_mount, bma->tp,
 					bma->ip, whichfork);
-		bma->cur->bc_private.b.firstblock = bma->tp->t_firstblock;
 	}
 	mval->br_state = (mval->br_state == XFS_EXT_UNWRITTEN)
 				? XFS_EXT_NORM : XFS_EXT_UNWRITTEN;
@@ -4458,13 +4450,6 @@ xfs_bmapi_write(
 		xfs_trans_log_inode(tp, ip, bma.logflags);
 
 	if (bma.cur) {
-		if (!error) {
-			ASSERT(tp->t_firstblock == NULLFSBLOCK ||
-			       XFS_FSB_TO_AGNO(mp, tp->t_firstblock) <=
-			       XFS_FSB_TO_AGNO(mp,
-				       bma.cur->bc_private.b.firstblock));
-			tp->t_firstblock = bma.cur->bc_private.b.firstblock;
-		}
 		xfs_btree_del_cursor(bma.cur,
 			error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
 	}
@@ -4528,7 +4513,6 @@ xfs_bmapi_remap(
 
 	if (ifp->if_flags & XFS_IFBROOT) {
 		cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
-		cur->bc_private.b.firstblock = tp->t_firstblock;
 		cur->bc_private.b.flags = 0;
 	}
 
@@ -5189,7 +5173,6 @@ __xfs_bunmapi(
 	if (ifp->if_flags & XFS_IFBROOT) {
 		ASSERT(XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_BTREE);
 		cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
-		cur->bc_private.b.firstblock = tp->t_firstblock;
 		cur->bc_private.b.flags = 0;
 	} else
 		cur = NULL;
@@ -5457,10 +5440,8 @@ __xfs_bunmapi(
 	if (logflags)
 		xfs_trans_log_inode(tp, ip, logflags);
 	if (cur) {
-		if (!error) {
-			tp->t_firstblock = cur->bc_private.b.firstblock;
+		if (!error)
 			cur->bc_private.b.allocated = 0;
-		}
 		xfs_btree_del_cursor(cur,
 			error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
 	}
@@ -5676,7 +5657,6 @@ xfs_bmap_collapse_extents(
 
 	if (ifp->if_flags & XFS_IFBROOT) {
 		cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
-		cur->bc_private.b.firstblock = tp->t_firstblock;
 		cur->bc_private.b.flags = 0;
 	}
 
@@ -5796,7 +5776,6 @@ xfs_bmap_insert_extents(
 
 	if (ifp->if_flags & XFS_IFBROOT) {
 		cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
-		cur->bc_private.b.firstblock = tp->t_firstblock;
 		cur->bc_private.b.flags = 0;
 	}
 
@@ -5918,7 +5897,6 @@ xfs_bmap_split_extent_at(
 
 	if (ifp->if_flags & XFS_IFBROOT) {
 		cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
-		cur->bc_private.b.firstblock = tp->t_firstblock;
 		cur->bc_private.b.flags = 0;
 		error = xfs_bmbt_lookup_eq(cur, &got, &i);
 		if (error)

fs/xfs/libxfs/xfs_bmap_btree.c

@@ -175,7 +175,6 @@ xfs_bmbt_dup_cursor(
 	 * Copy the firstblock, dfops, and flags values,
 	 * since init cursor doesn't get them.
 	 */
-	new->bc_private.b.firstblock = cur->bc_private.b.firstblock;
 	new->bc_private.b.flags = cur->bc_private.b.flags;
 
 	return new;
@@ -186,11 +185,11 @@ xfs_bmbt_update_cursor(
 	struct xfs_btree_cur	*src,
 	struct xfs_btree_cur	*dst)
 {
-	ASSERT((dst->bc_private.b.firstblock != NULLFSBLOCK) ||
+	ASSERT((dst->bc_tp->t_firstblock != NULLFSBLOCK) ||
 	       (dst->bc_private.b.ip->i_d.di_flags & XFS_DIFLAG_REALTIME));
 
 	dst->bc_private.b.allocated += src->bc_private.b.allocated;
-	dst->bc_private.b.firstblock = src->bc_private.b.firstblock;
+	dst->bc_tp->t_firstblock = src->bc_tp->t_firstblock;
 
 	src->bc_private.b.allocated = 0;
 }
@@ -208,7 +207,7 @@ xfs_bmbt_alloc_block(
 	memset(&args, 0, sizeof(args));
 	args.tp = cur->bc_tp;
 	args.mp = cur->bc_mp;
-	args.fsbno = cur->bc_private.b.firstblock;
+	args.fsbno = cur->bc_tp->t_firstblock;
 	args.firstblock = args.fsbno;
 	xfs_rmap_ino_bmbt_owner(&args.oinfo, cur->bc_private.b.ip->i_ino,
 			cur->bc_private.b.whichfork);
@@ -263,7 +262,7 @@ xfs_bmbt_alloc_block(
 	}
 
 	ASSERT(args.len == 1);
-	cur->bc_private.b.firstblock = args.fsbno;
+	cur->bc_tp->t_firstblock = args.fsbno;
 	cur->bc_private.b.allocated++;
 	cur->bc_private.b.ip->i_d.di_nblocks++;
 	xfs_trans_log_inode(args.tp, cur->bc_private.b.ip, XFS_ILOG_CORE);
@@ -562,7 +561,6 @@ xfs_bmbt_init_cursor(
 
 	cur->bc_private.b.forksize = XFS_IFORK_SIZE(ip, whichfork);
 	cur->bc_private.b.ip = ip;
-	cur->bc_private.b.firstblock = NULLFSBLOCK;
 	cur->bc_private.b.allocated = 0;
 	cur->bc_private.b.flags = 0;
 	cur->bc_private.b.whichfork = whichfork;

fs/xfs/libxfs/xfs_btree.h

@@ -214,7 +214,6 @@ typedef struct xfs_btree_cur
 		} a;
 		struct {			/* needed for BMAP */
 			struct xfs_inode *ip;	/* pointer to our inode */
-			xfs_fsblock_t	firstblock;	/* 1st blk allocated */
 			int		allocated;	/* count of alloced */
 			short		forksize;	/* fork's inode space */
 			char		whichfork;	/* data or attr fork */