50  * FUNCTION:	allocate an extent for a specified page range within a
55  *	xlen	- requested extent length.
58  *		  extent that is used as an allocation hint if the
60  *		  the xad describes the newly allocated extent.
61  *	abnr	- bool indicating whether the newly allocated extent
88 	/* validate extent length */  in extAlloc()
92 	/* get the page's starting extent offset */  in extAlloc()
97 		/* get the size of the extent described by the hint */  in extAlloc()
102 		 * request and if hint extent has the same abnr  in extAlloc()
104 		 * extend the hint extent to include the current  in extAlloc()
105 		 * extent if we can allocate the blocks immediately  in extAlloc()
106 		 * following the hint extent.  in extAlloc()
112 		/* adjust the hint to the last block of the extent */  in extAlloc()
116 	/* allocate the disk blocks for the extent.  initially, extBalloc()  in extAlloc()
120 	 * extent), with this smaller number of blocks consisting of the  in extAlloc()
140 	/* determine the value of the extent flag */  in extAlloc()
143 	/* if we can extend the hint extent to cover the current request,  in extAlloc()
144 	 * extend it.  otherwise, insert a new extent to  in extAlloc()
162 	/* set the results of the extent allocation */  in extAlloc()
185  * FUNCTION:	produce an extent allocation hint for a file offset.
210 	/* determine the starting extent offset of the page previous  in extHint()
270 	/* update the extent */  in extRecord()
280  * FUNCTION:	allocate disk blocks to form an extent.
285  *		a smaller number of blocks (producing a smaller extent), with