xfs: add group based bno conversion helpers

Add/move the blocks, blklog and blkmask fields to the generic groups
structure so that code can work with AGs and RTGs by just using the
right index into the array.

Then, add convenience helpers to convert block numbers based on the
generic group.  This will allow writing code that doesn't care if it is
used on AGs or the upcoming realtime groups.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

Author: Christoph Hellwig

fs/xfs/libxfs/xfs_group.c

@@ -214,3 +214,12 @@ xfs_group_insert(
 #endif
 	return error;
 }
+
+struct xfs_group *
+xfs_group_get_by_fsb(
+	struct xfs_mount	*mp,
+	xfs_fsblock_t		fsbno,
+	enum xfs_group_type	type)
+{
+	return xfs_group_get(mp, xfs_fsb_to_gno(mp, fsbno, type), type);
+}

fs/xfs/libxfs/xfs_group.h

@@ -46,6 +46,8 @@ struct xfs_group {
 
 struct xfs_group *xfs_group_get(struct xfs_mount *mp, uint32_t index,
 		enum xfs_group_type type);
+struct xfs_group *xfs_group_get_by_fsb(struct xfs_mount *mp,
+		xfs_fsblock_t fsbno, enum xfs_group_type type);
 struct xfs_group *xfs_group_hold(struct xfs_group *xg);
 void xfs_group_put(struct xfs_group *xg);
 
@@ -72,4 +74,58 @@ int xfs_group_insert(struct xfs_mount *mp, struct xfs_group *xg,
 #define xfs_group_marked(_mp, _type, _mark) \
 	xa_marked(&(_mp)->m_groups[(_type)].xa, (_mark))
 
+static inline xfs_agblock_t
+xfs_group_max_blocks(
+	struct xfs_group	*xg)
+{
+	return xg->xg_mount->m_groups[xg->xg_type].blocks;
+}
+
+static inline xfs_fsblock_t
+xfs_group_start_fsb(
+	struct xfs_group	*xg)
+{
+	return ((xfs_fsblock_t)xg->xg_gno) <<
+		xg->xg_mount->m_groups[xg->xg_type].blklog;
+}
+
+static inline xfs_fsblock_t
+xfs_gbno_to_fsb(
+	struct xfs_group	*xg,
+	xfs_agblock_t		gbno)
+{
+	return xfs_group_start_fsb(xg) | gbno;
+}
+
+static inline xfs_daddr_t
+xfs_gbno_to_daddr(
+	struct xfs_group	*xg,
+	xfs_agblock_t		gbno)
+{
+	struct xfs_mount	*mp = xg->xg_mount;
+	uint32_t		blocks = mp->m_groups[xg->xg_type].blocks;
+
+	return XFS_FSB_TO_BB(mp, (xfs_fsblock_t)xg->xg_gno * blocks + gbno);
+}
+
+static inline uint32_t
+xfs_fsb_to_gno(
+	struct xfs_mount	*mp,
+	xfs_fsblock_t		fsbno,
+	enum xfs_group_type	type)
+{
+	if (!mp->m_groups[type].blklog)
+		return 0;
+	return fsbno >> mp->m_groups[type].blklog;
+}
+
+static inline xfs_agblock_t
+xfs_fsb_to_gbno(
+	struct xfs_mount	*mp,
+	xfs_fsblock_t		fsbno,
+	enum xfs_group_type	type)
+{
+	return fsbno & mp->m_groups[type].blkmask;
+}
+
 #endif /* __LIBXFS_GROUP_H */

fs/xfs/libxfs/xfs_sb.c

@@ -988,6 +988,8 @@ xfs_sb_mount_common(
 	struct xfs_mount	*mp,
 	struct xfs_sb		*sbp)
 {
+	struct xfs_groups	*ags = &mp->m_groups[XG_TYPE_AG];
+
 	mp->m_agfrotor = 0;
 	atomic_set(&mp->m_agirotor, 0);
 	mp->m_maxagi = mp->m_sb.sb_agcount;
@@ -998,6 +1000,11 @@ xfs_sb_mount_common(
 	mp->m_blockmask = sbp->sb_blocksize - 1;
 	mp->m_blockwsize = sbp->sb_blocksize >> XFS_WORDLOG;
 	mp->m_blockwmask = mp->m_blockwsize - 1;
+
+	ags->blocks = mp->m_sb.sb_agblocks;
+	ags->blklog = mp->m_sb.sb_agblklog;
+	ags->blkmask = xfs_mask32lo(mp->m_sb.sb_agblklog);
+
 	xfs_mount_sb_set_rextsize(mp, sbp);
 
 	mp->m_alloc_mxr[0] = xfs_allocbt_maxrecs(mp, sbp->sb_blocksize, true);

fs/xfs/xfs_mount.h

@@ -71,8 +71,38 @@ struct xfs_inodegc {
 	unsigned int		cpu;
 };
 
+/*
+ * Container for each type of groups, used to look up individual groups and
+ * describes the geometry.
+ */
 struct xfs_groups {
 	struct xarray		xa;
+
+	/*
+	 * Maximum capacity of the group in FSBs.
+	 *
+	 * Each group is laid out densely in the daddr space.  For the
+	 * degenerate case of a pre-rtgroups filesystem, the incore rtgroup
+	 * pretends to have a zero-block and zero-blklog rtgroup.
+	 */
+	uint32_t		blocks;
+
+	/*
+	 * Log(2) of the logical size of each group.
+	 *
+	 * Compared to the blocks field above this is rounded up to the next
+	 * power of two, and thus lays out the xfs_fsblock_t/xfs_rtblock_t
+	 * space sparsely with a hole from blocks to (1 << blklog) at the end
+	 * of each group.
+	 */
+	uint8_t			blklog;
+
+	/*
+	 * Mask to extract the group-relative block number from a FSB.
+	 * For a pre-rtgroups filesystem we pretend to have one very large
+	 * rtgroup, so this mask must be 64-bit.
+	 */
+	uint64_t		blkmask;
 };
 
 /*