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Commit 65f1eaea authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Lachlan McIlroy
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[XFS] add helpers for addressing entities inside a btree block 



Add new helpers in xfs_btree.c to find the record, key and block pointer
entries inside a btree block. To implement this genericly the
->get_maxrecs methods and two new xfs_btree_ops entries for the key and
record sizes are used. Also add a big comment describing how the
addressing inside a btree block works.

Note that these helpers are unused until users are introduced in the next
patches and this patch will thus cause some harmless compiler warnings.

SGI-PV: 985583

SGI-Modid: xfs-linux-melb:xfs-kern:32189a

Signed-off-by: default avatarChristoph Hellwig <hch@infradead.org>
Signed-off-by: default avatarLachlan McIlroy <lachlan@sgi.com>
Signed-off-by: default avatarBill O'Donnell <billodo@sgi.com>
Signed-off-by: default avatarDavid Chinner <david@fromorbit.com>
parent ce5e42db

fs/xfs/xfs_alloc_btree.c

+3 −0
Original line number Diff line number Diff line
@@ -2294,6 +2294,9 @@ xfs_allocbt_trace_record( 
#endif /* XFS_BTREE_TRACE */



static const struct xfs_btree_ops xfs_allocbt_ops = {

	.rec_len		= sizeof(xfs_alloc_rec_t),

	.key_len		= sizeof(xfs_alloc_key_t),



	.dup_cursor		= xfs_allocbt_dup_cursor,

	.get_maxrecs		= xfs_allocbt_get_maxrecs,

fs/xfs/xfs_bmap_btree.c

+3 −0
Original line number Diff line number Diff line
@@ -2509,6 +2509,9 @@ xfs_bmbt_trace_record( 
#endif /* XFS_BTREE_TRACE */



static const struct xfs_btree_ops xfs_bmbt_ops = {

	.rec_len		= sizeof(xfs_bmbt_rec_t),

	.key_len		= sizeof(xfs_bmbt_key_t),



	.dup_cursor		= xfs_bmbt_dup_cursor,

	.get_maxrecs		= xfs_bmbt_get_maxrecs,

fs/xfs/xfs_btree.c

+130 −0
Original line number Diff line number Diff line
@@ -402,6 +402,136 @@ xfs_btree_dup_cursor( 
	return 0;

}



/*

 * XFS btree block layout and addressing:

 *

 * There are two types of blocks in the btree: leaf and non-leaf blocks.

 *

 * The leaf record start with a header then followed by records containing

 * the values.  A non-leaf block also starts with the same header, and

 * then first contains lookup keys followed by an equal number of pointers

 * to the btree blocks at the previous level.

 *

 *		+--------+-------+-------+-------+-------+-------+-------+

 * Leaf:	| header | rec 1 | rec 2 | rec 3 | rec 4 | rec 5 | rec N |

 *		+--------+-------+-------+-------+-------+-------+-------+

 *

 *		+--------+-------+-------+-------+-------+-------+-------+

 * Non-Leaf:	| header | key 1 | key 2 | key N | ptr 1 | ptr 2 | ptr N |

 *		+--------+-------+-------+-------+-------+-------+-------+

 *

 * The header is called struct xfs_btree_block for reasons better left unknown

 * and comes in different versions for short (32bit) and long (64bit) block

 * pointers.  The record and key structures are defined by the btree instances

 * and opaque to the btree core.  The block pointers are simple disk endian

 * integers, available in a short (32bit) and long (64bit) variant.

 *

 * The helpers below calculate the offset of a given record, key or pointer

 * into a btree block (xfs_btree_*_offset) or return a pointer to the given

 * record, key or pointer (xfs_btree_*_addr).  Note that all addressing

 * inside the btree block is done using indices starting at one, not zero!

 */



/*

 * Return size of the btree block header for this btree instance.

 */

static inline size_t xfs_btree_block_len(struct xfs_btree_cur *cur)

{

	return (cur->bc_flags & XFS_BTREE_LONG_PTRS) ?

		sizeof(struct xfs_btree_lblock) :

		sizeof(struct xfs_btree_sblock);

}



/*

 * Return size of btree block pointers for this btree instance.

 */

static inline size_t xfs_btree_ptr_len(struct xfs_btree_cur *cur)

{

	return (cur->bc_flags & XFS_BTREE_LONG_PTRS) ?

		sizeof(__be64) : sizeof(__be32);

}



/*

 * Calculate offset of the n-th record in a btree block.

 */

STATIC size_t

xfs_btree_rec_offset(

	struct xfs_btree_cur	*cur,

	int			n)

{

	return xfs_btree_block_len(cur) +

		(n - 1) * cur->bc_ops->rec_len;

}



/*

 * Calculate offset of the n-th key in a btree block.

 */

STATIC size_t

xfs_btree_key_offset(

	struct xfs_btree_cur	*cur,

	int			n)

{

	return xfs_btree_block_len(cur) +

		(n - 1) * cur->bc_ops->key_len;

}



/*

 * Calculate offset of the n-th block pointer in a btree block.

 */

STATIC size_t

xfs_btree_ptr_offset(

	struct xfs_btree_cur	*cur,

	int			n,

	int			level)

{

	return xfs_btree_block_len(cur) +

		cur->bc_ops->get_maxrecs(cur, level) * cur->bc_ops->key_len +

		(n - 1) * xfs_btree_ptr_len(cur);

}



/*

 * Return a pointer to the n-th record in the btree block.

 */

STATIC union xfs_btree_rec *

xfs_btree_rec_addr(

	struct xfs_btree_cur	*cur,

	int			n,

	struct xfs_btree_block	*block)

{

	return (union xfs_btree_rec *)

		((char *)block + xfs_btree_rec_offset(cur, n));

}



/*

 * Return a pointer to the n-th key in the btree block.

 */

STATIC union xfs_btree_key *

xfs_btree_key_addr(

	struct xfs_btree_cur	*cur,

	int			n,

	struct xfs_btree_block	*block)

{

	return (union xfs_btree_key *)

		((char *)block + xfs_btree_key_offset(cur, n));

}



/*

 * Return a pointer to the n-th block pointer in the btree block.

 */

STATIC union xfs_btree_ptr *

xfs_btree_ptr_addr(

	struct xfs_btree_cur	*cur,

	int			n,

	struct xfs_btree_block	*block)

{

	int			level = xfs_btree_get_level(block);



	ASSERT(block->bb_level != 0);



	return (union xfs_btree_ptr *)

		((char *)block + xfs_btree_ptr_offset(cur, n, level));

}



/*

 * Get a the root block which is stored in the inode.

 *

fs/xfs/xfs_btree.h

+13 −0
Original line number Diff line number Diff line
@@ -180,6 +180,10 @@ do { \ 
#define	XFS_BTREE_MAXLEVELS	8	/* max of all btrees */



struct xfs_btree_ops {

	/* size of the key and record structures */

	size_t	key_len;

	size_t	rec_len;



	/* cursor operations */

	struct xfs_btree_cur *(*dup_cursor)(struct xfs_btree_cur *);
@@ -497,6 +501,15 @@ xfs_btree_setbuf( 
	int			lev,	/* level in btree */

	struct xfs_buf		*bp);	/* new buffer to set */





/*

 * Helpers.

 */

static inline int xfs_btree_get_level(struct xfs_btree_block *block)

{

	return be16_to_cpu(block->bb_level);

}



#endif	/* __KERNEL__ */

fs/xfs/xfs_ialloc_btree.c

+3 −0
Original line number Diff line number Diff line
@@ -2160,6 +2160,9 @@ xfs_inobt_trace_record( 
#endif /* XFS_BTREE_TRACE */



static const struct xfs_btree_ops xfs_inobt_ops = {

	.rec_len		= sizeof(xfs_inobt_rec_t),

	.key_len		= sizeof(xfs_inobt_key_t),



	.dup_cursor		= xfs_inobt_dup_cursor,

	.get_maxrecs		= xfs_inobt_get_maxrecs,