xfs: Refactoring the nagcount and delta calculation

Introduce xfs_growfs_compute_delta() to calculate the nagcount
and delta blocks and refactor the code from xfs_growfs_data_private().
No functional changes.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nirjhar Roy (IBM) <nirjhar.roy.lists@gmail.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

Author: Nirjhar-Roy-0211

fs/xfs/libxfs/xfs_ag.c

@@ -872,6 +872,34 @@ xfs_ag_shrink_space(
 	return err2;
 }
 
+void
+xfs_growfs_compute_deltas(
+	struct xfs_mount	*mp,
+	xfs_rfsblock_t		nb,
+	int64_t			*deltap,
+	xfs_agnumber_t		*nagcountp)
+{
+	xfs_rfsblock_t	nb_div, nb_mod;
+	int64_t		delta;
+	xfs_agnumber_t	nagcount;
+
+	nb_div = nb;
+	nb_mod = do_div(nb_div, mp->m_sb.sb_agblocks);
+	if (nb_mod && nb_mod >= XFS_MIN_AG_BLOCKS)
+		nb_div++;
+	else if (nb_mod)
+		nb = nb_div * mp->m_sb.sb_agblocks;
+
+	if (nb_div > XFS_MAX_AGNUMBER + 1) {
+		nb_div = XFS_MAX_AGNUMBER + 1;
+		nb = nb_div * mp->m_sb.sb_agblocks;
+	}
+	nagcount = nb_div;
+	delta = nb - mp->m_sb.sb_dblocks;
+	*deltap = delta;
+	*nagcountp = nagcount;
+}
+
 /*
  * Extent the AG indicated by the @id by the length passed in
  */

fs/xfs/libxfs/xfs_ag.h

@@ -331,6 +331,9 @@ struct aghdr_init_data {
 int xfs_ag_init_headers(struct xfs_mount *mp, struct aghdr_init_data *id);
 int xfs_ag_shrink_space(struct xfs_perag *pag, struct xfs_trans **tpp,
 			xfs_extlen_t delta);
+void
+xfs_growfs_compute_deltas(struct xfs_mount *mp, xfs_rfsblock_t nb,
+			int64_t *deltap, xfs_agnumber_t *nagcountp);
 int xfs_ag_extend_space(struct xfs_perag *pag, struct xfs_trans *tp,
 			xfs_extlen_t len);
 int xfs_ag_get_geometry(struct xfs_perag *pag, struct xfs_ag_geometry *ageo);

fs/xfs/xfs_fsops.c

@@ -95,18 +95,17 @@ xfs_growfs_data_private(
 	struct xfs_growfs_data	*in)		/* growfs data input struct */
 {
 	xfs_agnumber_t		oagcount = mp->m_sb.sb_agcount;
+	xfs_rfsblock_t		nb = in->newblocks;
 	struct xfs_buf		*bp;
 	int			error;
 	xfs_agnumber_t		nagcount;
 	xfs_agnumber_t		nagimax = 0;
-	xfs_rfsblock_t		nb, nb_div, nb_mod;
 	int64_t			delta;
 	bool			lastag_extended = false;
 	struct xfs_trans	*tp;
 	struct aghdr_init_data	id = {};
 	struct xfs_perag	*last_pag;
 
-	nb = in->newblocks;
 	error = xfs_sb_validate_fsb_count(&mp->m_sb, nb);
 	if (error)
 		return error;
@@ -125,20 +124,8 @@ xfs_growfs_data_private(
 			mp->m_sb.sb_rextsize);
 	if (error)
 		return error;
+	xfs_growfs_compute_deltas(mp, nb, &delta, &nagcount);
 
-	nb_div = nb;
-	nb_mod = do_div(nb_div, mp->m_sb.sb_agblocks);
-	if (nb_mod && nb_mod >= XFS_MIN_AG_BLOCKS)
-		nb_div++;
-	else if (nb_mod)
-		nb = nb_div * mp->m_sb.sb_agblocks;
-
-	if (nb_div > XFS_MAX_AGNUMBER + 1) {
-		nb_div = XFS_MAX_AGNUMBER + 1;
-		nb = nb_div * mp->m_sb.sb_agblocks;
-	}
-	nagcount = nb_div;
-	delta = nb - mp->m_sb.sb_dblocks;
 	/*
 	 * Reject filesystems with a single AG because they are not
 	 * supported, and reject a shrink operation that would cause a