xfs: clean up buffer get/read call API

The xfs_buf_get/read API is not consistent in the units it uses, and
does not use appropriate or consistent units/types for the
variables.

Convert the API to use disk addresses and block counts for all
buffer get and read calls. Use consistent naming for all the
functions and their declarations, and convert the internal functions
to use disk addresses and block counts to avoid need to convert them
from one type to another and back again.

Fix all the callers to use disk addresses and block counts. In many
cases, this removes an additional conversion from the function call
as the callers already have a block count.

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>

1 files changed, 46 insertions, 40 deletions

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index f463dce..d3a1974 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -172,8 +172,8 @@ xfs_buf_stale(
 struct xfs_buf *
 xfs_buf_alloc(
 	struct xfs_buftarg	*target,
-	xfs_off_t		range_base,
-	size_t			range_length,
+	xfs_daddr_t		blkno,
+	size_t			numblks,
 	xfs_buf_flags_t		flags)
 {
 	struct xfs_buf		*bp;
@@ -196,14 +196,21 @@ xfs_buf_alloc(
 	sema_init(&bp->b_sema, 0); /* held, no waiters */
 	XB_SET_OWNER(bp);
 	bp->b_target = target;
-	bp->b_file_offset = range_base;
+	bp->b_file_offset = blkno << BBSHIFT;
 	/*
 	 * Set buffer_length and count_desired to the same value initially.
 	 * I/O routines should use count_desired, which will be the same in
 	 * most cases but may be reset (e.g. XFS recovery).
 	 */
-	bp->b_buffer_length = bp->b_count_desired = range_length;
+	bp->b_buffer_length = bp->b_count_desired = numblks << BBSHIFT;
 	bp->b_flags = flags;
+
+	/*
+	 * We do not set the block number here in the buffer because we have not
+	 * finished initialising the buffer. We insert the buffer into the cache
+	 * in this state, so this ensures that we are unable to do IO on a
+	 * buffer that hasn't been fully initialised.
+	 */
 	bp->b_bn = XFS_BUF_DADDR_NULL;
 	atomic_set(&bp->b_pin_count, 0);
 	init_waitqueue_head(&bp->b_waiters);
@@ -426,29 +433,29 @@ _xfs_buf_map_pages(
  */
 xfs_buf_t *
 _xfs_buf_find(
-	xfs_buftarg_t		*btp,	/* block device target		*/
-	xfs_off_t		ioff,	/* starting offset of range	*/
-	size_t			isize,	/* length of range		*/
+	struct xfs_buftarg	*btp,
+	xfs_daddr_t		blkno,
+	size_t			numblks,
 	xfs_buf_flags_t		flags,
 	xfs_buf_t		*new_bp)
 {
-	xfs_off_t		range_base;
-	size_t			range_length;
+	xfs_off_t		offset;
+	size_t			numbytes;
 	struct xfs_perag	*pag;
 	struct rb_node		**rbp;
 	struct rb_node		*parent;
 	xfs_buf_t		*bp;
 
-	range_base = (ioff << BBSHIFT);
-	range_length = (isize << BBSHIFT);
+	offset = BBTOB(blkno);
+	numbytes = BBTOB(numblks);
 
 	/* Check for IOs smaller than the sector size / not sector aligned */
-	ASSERT(!(range_length < (1 << btp->bt_sshift)));
-	ASSERT(!(range_base & (xfs_off_t)btp->bt_smask));
+	ASSERT(!(numbytes < (1 << btp->bt_sshift)));
+	ASSERT(!(offset & (xfs_off_t)btp->bt_smask));
 
 	/* get tree root */
 	pag = xfs_perag_get(btp->bt_mount,
-				xfs_daddr_to_agno(btp->bt_mount, ioff));
+				xfs_daddr_to_agno(btp->bt_mount, blkno));
 
 	/* walk tree */
 	spin_lock(&pag->pag_buf_lock);
@@ -459,9 +466,9 @@ _xfs_buf_find(
 		parent = *rbp;
 		bp = rb_entry(parent, struct xfs_buf, b_rbnode);
 
-		if (range_base < bp->b_file_offset)
+		if (offset < bp->b_file_offset)
 			rbp = &(*rbp)->rb_left;
-		else if (range_base > bp->b_file_offset)
+		else if (offset > bp->b_file_offset)
 			rbp = &(*rbp)->rb_right;
 		else {
 			/*
@@ -472,7 +479,7 @@ _xfs_buf_find(
 			 * reallocating a busy extent. Skip this buffer and
 			 * continue searching to the right for an exact match.
 			 */
-			if (bp->b_buffer_length != range_length) {
+			if (bp->b_buffer_length != numbytes) {
 				ASSERT(bp->b_flags & XBF_STALE);
 				rbp = &(*rbp)->rb_right;
 				continue;
@@ -532,21 +539,20 @@ found:
  */
 struct xfs_buf *
 xfs_buf_get(
-	xfs_buftarg_t		*target,/* target for buffer		*/
-	xfs_off_t		ioff,	/* starting offset of range	*/
-	size_t			isize,	/* length of range		*/
+	xfs_buftarg_t		*target,
+	xfs_daddr_t		blkno,
+	size_t			numblks,
 	xfs_buf_flags_t		flags)
 {
 	struct xfs_buf		*bp;
 	struct xfs_buf		*new_bp;
 	int			error = 0;
 
-	bp = _xfs_buf_find(target, ioff, isize, flags, NULL);
+	bp = _xfs_buf_find(target, blkno, numblks, flags, NULL);
 	if (likely(bp))
 		goto found;
 
-	new_bp = xfs_buf_alloc(target, ioff << BBSHIFT, isize << BBSHIFT,
-			       flags);
+	new_bp = xfs_buf_alloc(target, blkno, numblks, flags);
 	if (unlikely(!new_bp))
 		return NULL;
 
@@ -556,7 +562,7 @@ xfs_buf_get(
 		return NULL;
 	}
 
-	bp = _xfs_buf_find(target, ioff, isize, flags, new_bp);
+	bp = _xfs_buf_find(target, blkno, numblks, flags, new_bp);
 	if (!bp) {
 		xfs_buf_free(new_bp);
 		return NULL;
@@ -569,7 +575,7 @@ xfs_buf_get(
 	 * Now we have a workable buffer, fill in the block number so
 	 * that we can do IO on it.
 	 */
-	bp->b_bn = ioff;
+	bp->b_bn = blkno;
 	bp->b_count_desired = bp->b_buffer_length;
 
 found:
@@ -613,15 +619,15 @@ _xfs_buf_read(
 xfs_buf_t *
 xfs_buf_read(
 	xfs_buftarg_t		*target,
-	xfs_off_t		ioff,
-	size_t			isize,
+	xfs_daddr_t		blkno,
+	size_t			numblks,
 	xfs_buf_flags_t		flags)
 {
 	xfs_buf_t		*bp;
 
 	flags |= XBF_READ;
 
-	bp = xfs_buf_get(target, ioff, isize, flags);
+	bp = xfs_buf_get(target, blkno, numblks, flags);
 	if (bp) {
 		trace_xfs_buf_read(bp, flags, _RET_IP_);
 
@@ -656,13 +662,13 @@ xfs_buf_read(
 void
 xfs_buf_readahead(
 	xfs_buftarg_t		*target,
-	xfs_off_t		ioff,
-	size_t			isize)
+	xfs_daddr_t		blkno,
+	size_t			numblks)
 {
 	if (bdi_read_congested(target->bt_bdi))
 		return;
 
-	xfs_buf_read(target, ioff, isize,
+	xfs_buf_read(target, blkno, numblks,
 		     XBF_TRYLOCK|XBF_ASYNC|XBF_READ_AHEAD|XBF_DONT_BLOCK);
 }
 
@@ -672,16 +678,15 @@ xfs_buf_readahead(
  */
 struct xfs_buf *
 xfs_buf_read_uncached(
-	struct xfs_mount	*mp,
 	struct xfs_buftarg	*target,
 	xfs_daddr_t		daddr,
-	size_t			length,
+	size_t			numblks,
 	int			flags)
 {
 	xfs_buf_t		*bp;
 	int			error;
 
-	bp = xfs_buf_get_uncached(target, length, flags);
+	bp = xfs_buf_get_uncached(target, numblks, flags);
 	if (!bp)
 		return NULL;
 
@@ -689,7 +694,7 @@ xfs_buf_read_uncached(
 	XFS_BUF_SET_ADDR(bp, daddr);
 	XFS_BUF_READ(bp);
 
-	xfsbdstrat(mp, bp);
+	xfsbdstrat(target->bt_mount, bp);
 	error = xfs_buf_iowait(bp);
 	if (error) {
 		xfs_buf_relse(bp);
@@ -705,7 +710,7 @@ xfs_buf_read_uncached(
 void
 xfs_buf_set_empty(
 	struct xfs_buf		*bp,
-	size_t			len)
+	size_t			numblks)
 {
 	if (bp->b_pages)
 		_xfs_buf_free_pages(bp);
@@ -714,7 +719,7 @@ xfs_buf_set_empty(
 	bp->b_page_count = 0;
 	bp->b_addr = NULL;
 	bp->b_file_offset = 0;
-	bp->b_buffer_length = bp->b_count_desired = len;
+	bp->b_buffer_length = bp->b_count_desired = numblks << BBSHIFT;
 	bp->b_bn = XFS_BUF_DADDR_NULL;
 	bp->b_flags &= ~XBF_MAPPED;
 }
@@ -776,17 +781,18 @@ xfs_buf_associate_memory(
 xfs_buf_t *
 xfs_buf_get_uncached(
 	struct xfs_buftarg	*target,
-	size_t			len,
+	size_t			numblks,
 	int			flags)
 {
-	unsigned long		page_count = PAGE_ALIGN(len) >> PAGE_SHIFT;
+	unsigned long		page_count;
 	int			error, i;
 	xfs_buf_t		*bp;
 
-	bp = xfs_buf_alloc(target, 0, len, 0);
+	bp = xfs_buf_alloc(target, 0, numblks, 0);
 	if (unlikely(bp == NULL))
 		goto fail;
 
+	page_count = PAGE_ALIGN(numblks << BBSHIFT) >> PAGE_SHIFT;
 	error = _xfs_buf_get_pages(bp, page_count, 0);
 	if (error)
 		goto fail_free_buf;