xfs: simplify the xfs_bmap_btree_to_extents calling conventions

Move boilerplate code from the callers into xfs_bmap_btree_to_extents:

 - exit early without failure if we don't need to convert to the
   extent format
 - assert that we have a btree cursor
 - don't reinitialize the passed in logflags argument
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
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

@@ -577,42 +577,44 @@ __xfs_bmap_add_free(
  */
 
 /*
- * Transform a btree format file with only one leaf node, where the
- * extents list will fit in the inode, into an extents format file.
- * Since the file extents are already in-core, all we have to do is
- * give up the space for the btree root and pitch the leaf block.
+ * Convert the inode format to extent format if it currently is in btree format,
+ * but the extent list is small enough that it fits into the extent format.
+ *
+ * Since the extents are already in-core, all we have to do is give up the space
+ * for the btree root and pitch the leaf block.
  */
 STATIC int				/* error */
 xfs_bmap_btree_to_extents(
-	xfs_trans_t		*tp,	/* transaction pointer */
-	xfs_inode_t		*ip,	/* incore inode pointer */
-	xfs_btree_cur_t		*cur,	/* btree cursor */
+	struct xfs_trans	*tp,	/* transaction pointer */
+	struct xfs_inode	*ip,	/* incore inode pointer */
+	struct xfs_btree_cur	*cur,	/* btree cursor */
 	int			*logflagsp, /* inode logging flags */
 	int			whichfork)  /* data or attr fork */
 {
-	/* REFERENCED */
+	struct xfs_ifork	*ifp = XFS_IFORK_PTR(ip, whichfork);
+	struct xfs_mount	*mp = ip->i_mount;
+	struct xfs_btree_block	*rblock = ifp->if_broot;
 	struct xfs_btree_block	*cblock;/* child btree block */
 	xfs_fsblock_t		cbno;	/* child block number */
 	xfs_buf_t		*cbp;	/* child block's buffer */
 	int			error;	/* error return value */
-	struct xfs_ifork	*ifp;	/* inode fork data */
-	xfs_mount_t		*mp;	/* mount point structure */
 	__be64			*pp;	/* ptr to block address */
-	struct xfs_btree_block	*rblock;/* root btree block */
 	struct xfs_owner_info	oinfo;
 
-	mp = ip->i_mount;
-	ifp = XFS_IFORK_PTR(ip, whichfork);
+	/* check if we actually need the extent format first: */
+	if (!xfs_bmap_wants_extents(ip, whichfork))
+		return 0;
+
+	ASSERT(cur);
 	ASSERT(whichfork != XFS_COW_FORK);
 	ASSERT(ifp->if_flags & XFS_IFEXTENTS);
 	ASSERT(XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_BTREE);
-	rblock = ifp->if_broot;
 	ASSERT(be16_to_cpu(rblock->bb_level) == 1);
 	ASSERT(be16_to_cpu(rblock->bb_numrecs) == 1);
 	ASSERT(xfs_bmbt_maxrecs(mp, ifp->if_broot_bytes, 0) == 1);
+
 	pp = XFS_BMAP_BROOT_PTR_ADDR(mp, rblock, 1, ifp->if_broot_bytes);
 	cbno = be64_to_cpu(*pp);
-	*logflagsp = 0;
 #ifdef DEBUG
 	XFS_WANT_CORRUPTED_RETURN(cur->bc_mp,
 			xfs_btree_check_lptr(cur, cbno, 1));
@@ -635,7 +637,7 @@ xfs_bmap_btree_to_extents(
 	ASSERT(ifp->if_broot == NULL);
 	ASSERT((ifp->if_flags & XFS_IFBROOT) == 0);
 	XFS_IFORK_FMT_SET(ip, whichfork, XFS_DINODE_FMT_EXTENTS);
-	*logflagsp = XFS_ILOG_CORE | xfs_ilog_fext(whichfork);
+	*logflagsp |= XFS_ILOG_CORE | xfs_ilog_fext(whichfork);
 	return 0;
 }
 
@@ -4424,19 +4426,10 @@ xfs_bmapi_write(
 	}
 	*nmap = n;
 
-	/*
-	 * Transform from btree to extents, give it cur.
-	 */
-	if (xfs_bmap_wants_extents(ip, whichfork)) {
-		int		tmp_logflags = 0;
-
-		ASSERT(bma.cur);
-		error = xfs_bmap_btree_to_extents(tp, ip, bma.cur,
-			&tmp_logflags, whichfork);
-		bma.logflags |= tmp_logflags;
-		if (error)
-			goto error0;
-	}
+	error = xfs_bmap_btree_to_extents(tp, ip, bma.cur, &bma.logflags,
+			whichfork);
+	if (error)
+		goto error0;
 
 	ASSERT(XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE ||
 	       XFS_IFORK_NEXTENTS(ip, whichfork) >
@@ -4574,13 +4567,7 @@ xfs_bmapi_remap(
 	if (error)
 		goto error0;
 
-	if (xfs_bmap_wants_extents(ip, whichfork)) {
-		int		tmp_logflags = 0;
-
-		error = xfs_bmap_btree_to_extents(tp, ip, cur,
-			&tmp_logflags, whichfork);
-		logflags |= tmp_logflags;
-	}
+	error = xfs_bmap_btree_to_extents(tp, ip, cur, &logflags, whichfork);
 
 error0:
 	if (ip->i_d.di_format != XFS_DINODE_FMT_EXTENTS)
@@ -5444,24 +5431,11 @@ __xfs_bunmapi(
 		error = xfs_bmap_extents_to_btree(tp, ip, &cur, 0,
 				&tmp_logflags, whichfork);
 		logflags |= tmp_logflags;
-		if (error)
-			goto error0;
-	}
-	/*
-	 * transform from btree to extents, give it cur
-	 */
-	else if (xfs_bmap_wants_extents(ip, whichfork)) {
-		ASSERT(cur != NULL);
-		error = xfs_bmap_btree_to_extents(tp, ip, cur, &tmp_logflags,
+	} else {
+		error = xfs_bmap_btree_to_extents(tp, ip, cur, &logflags,
 			whichfork);
-		logflags |= tmp_logflags;
-		if (error)
-			goto error0;
 	}
-	/*
-	 * transform from extents to local?
-	 */
-	error = 0;
+
 error0:
 	/*
 	 * Log everything.  Do this after conversion, there's no point in