xfs: kill xfs_buf_btoc

xfs_buf_btoc and friends are simple macros that do basic block
to page index conversion and vice versa. These aren't widely used,
and we use open coded masking and shifting everywhere else. Hence
remove the macros and open code the work they do.

Also, use of PAGE_CACHE_{SIZE|SHIFT|MASK} for these macros is now
incorrect - we are using pages directly and not the page cache, so
use PAGE_{SIZE|MASK|SHIFT} instead.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

fs/xfs/xfs_buf.c

@@ -306,23 +306,23 @@ xfs_buf_allocate_memory(
 	size_t			nbytes, offset;
 	gfp_t			gfp_mask = xb_to_gfp(flags);
 	unsigned short		page_count, i;
-	xfs_off_t		end;
+	xfs_off_t		start, end;
 	int			error;
 
 	/*
 	 * for buffers that are contained within a single page, just allocate
 	 * the memory from the heap - there's no need for the complexity of
 	 * page arrays to keep allocation down to order 0.
 	 */
-	if (bp->b_length < BTOBB(PAGE_SIZE)) {
-		bp->b_addr = kmem_alloc(BBTOB(bp->b_length), xb_to_km(flags));
+	size = BBTOB(bp->b_length);
+	if (size < PAGE_SIZE) {
+		bp->b_addr = kmem_alloc(size, xb_to_km(flags));
 		if (!bp->b_addr) {
 			/* low memory - use alloc_page loop instead */
 			goto use_alloc_page;
 		}
 
-		if (((unsigned long)(bp->b_addr + BBTOB(bp->b_length) - 1) &
-								PAGE_MASK) !=
+		if (((unsigned long)(bp->b_addr + size - 1) & PAGE_MASK) !=
 		    ((unsigned long)bp->b_addr & PAGE_MASK)) {
 			/* b_addr spans two pages - use alloc_page instead */
 			kmem_free(bp->b_addr);
@@ -338,14 +338,14 @@ xfs_buf_allocate_memory(
 	}
 
 use_alloc_page:
-	end = BBTOB(bp->b_bn + bp->b_length);
-	page_count = xfs_buf_btoc(end) - xfs_buf_btoct(BBTOB(bp->b_bn));
+	start = BBTOB(bp->b_bn) >> PAGE_SHIFT;
+	end = (BBTOB(bp->b_bn + bp->b_length) + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	page_count = end - start;
 	error = _xfs_buf_get_pages(bp, page_count, flags);
 	if (unlikely(error))
 		return error;
 
 	offset = bp->b_offset;
-	size = BBTOB(bp->b_length);
 	bp->b_flags |= _XBF_PAGES;
 
 	for (i = 0; i < bp->b_page_count; i++) {
@@ -1320,27 +1320,30 @@ xfs_buf_iomove(
 	void			*data,	/* data address			*/
 	xfs_buf_rw_t		mode)	/* read/write/zero flag		*/
 {
-	size_t			bend, cpoff, csize;
-	struct page		*page;
+	size_t			bend;
 
 	bend = boff + bsize;
 	while (boff < bend) {
-		page = bp->b_pages[xfs_buf_btoct(boff + bp->b_offset)];
-		cpoff = xfs_buf_poff(boff + bp->b_offset);
-		csize = min_t(size_t,
-			      PAGE_SIZE - cpoff, BBTOB(bp->b_io_length) - boff);
+		struct page	*page;
+		int		page_index, page_offset, csize;
+
+		page_index = (boff + bp->b_offset) >> PAGE_SHIFT;
+		page_offset = (boff + bp->b_offset) & ~PAGE_MASK;
+		page = bp->b_pages[page_index];
+		csize = min_t(size_t, PAGE_SIZE - page_offset,
+				      BBTOB(bp->b_io_length) - boff);
 
-		ASSERT(((csize + cpoff) <= PAGE_SIZE));
+		ASSERT((csize + page_offset) <= PAGE_SIZE);
 
 		switch (mode) {
 		case XBRW_ZERO:
-			memset(page_address(page) + cpoff, 0, csize);
+			memset(page_address(page) + page_offset, 0, csize);
 			break;
 		case XBRW_READ:
-			memcpy(data, page_address(page) + cpoff, csize);
+			memcpy(data, page_address(page) + page_offset, csize);
 			break;
 		case XBRW_WRITE:
-			memcpy(page_address(page) + cpoff, data, csize);
+			memcpy(page_address(page) + page_offset, data, csize);
 		}
 
 		boff += csize;

fs/xfs/xfs_buf.h

@@ -32,11 +32,6 @@
 
 #define XFS_BUF_DADDR_NULL	((xfs_daddr_t) (-1LL))
 
-#define xfs_buf_ctob(pp)	((pp) * PAGE_CACHE_SIZE)
-#define xfs_buf_btoc(dd)	(((dd) + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT)
-#define xfs_buf_btoct(dd)	((dd) >> PAGE_CACHE_SHIFT)
-#define xfs_buf_poff(aa)	((aa) & ~PAGE_CACHE_MASK)
-
 typedef enum {
 	XBRW_READ = 1,			/* transfer into target memory */
 	XBRW_WRITE = 2,			/* transfer from target memory */