xfs: make imaxpct changes in growfs separate

When growfs changes the imaxpct value of the filesystem, it runs
through all the "change size" growfs code, whether it needs to or
not. Separate out changing imaxpct into it's own function and
transaction to simplify the rest of the growfs code.
Signed-Off-By: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_fsops.c

@@ -424,25 +424,21 @@ xfs_growfs_data_private(
 	xfs_agi_t		*agi;
 	xfs_agnumber_t		agno;
 	xfs_buf_t		*bp;
-	int			dpct;
 	int			error, saved_error = 0;
 	xfs_agnumber_t		nagcount;
 	xfs_agnumber_t		nagimax = 0;
 	xfs_rfsblock_t		nb, nb_mod;
 	xfs_rfsblock_t		new;
 	xfs_agnumber_t		oagcount;
-	int			pct;
 	xfs_trans_t		*tp;
 	LIST_HEAD		(buffer_list);
 	struct aghdr_init_data	id = {};
 
 	nb = in->newblocks;
-	pct = in->imaxpct;
-	if (nb < mp->m_sb.sb_dblocks || pct < 0 || pct > 100)
+	if (nb < mp->m_sb.sb_dblocks)
 		return -EINVAL;
 	if ((error = xfs_sb_validate_fsb_count(&mp->m_sb, nb)))
 		return error;
-	dpct = pct - mp->m_sb.sb_imax_pct;
 	error = xfs_buf_read_uncached(mp->m_ddev_targp,
 				XFS_FSB_TO_BB(mp, nb) - XFS_FSS_TO_BB(mp, 1),
 				XFS_FSS_TO_BB(mp, 1), 0, &bp, NULL);
@@ -575,8 +571,6 @@ xfs_growfs_data_private(
 				 nb - mp->m_sb.sb_dblocks);
 	if (id.nfree)
 		xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, id.nfree);
-	if (dpct)
-		xfs_trans_mod_sb(tp, XFS_TRANS_SB_IMAXPCT, dpct);
 	xfs_trans_set_sync(tp);
 	error = xfs_trans_commit(tp);
 	if (error)
@@ -585,12 +579,6 @@ xfs_growfs_data_private(
 	/* New allocation groups fully initialized, so update mount struct */
 	if (nagimax)
 		mp->m_maxagi = nagimax;
-	if (mp->m_sb.sb_imax_pct) {
-		uint64_t icount = mp->m_sb.sb_dblocks * mp->m_sb.sb_imax_pct;
-		do_div(icount, 100);
-		mp->m_maxicount = icount << mp->m_sb.sb_inopblog;
-	} else
-		mp->m_maxicount = 0;
 	xfs_set_low_space_thresholds(mp);
 	mp->m_alloc_set_aside = xfs_alloc_set_aside(mp);
 
@@ -694,25 +682,68 @@ xfs_growfs_log_private(
 	return -ENOSYS;
 }
 
+static int
+xfs_growfs_imaxpct(
+	struct xfs_mount	*mp,
+	__u32			imaxpct)
+{
+	struct xfs_trans	*tp;
+	int64_t			dpct;
+	int			error;
+
+	if (imaxpct > 100)
+		return -EINVAL;
+
+	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_growdata,
+			XFS_GROWFS_SPACE_RES(mp), 0, XFS_TRANS_RESERVE, &tp);
+	if (error)
+		return error;
+
+	dpct = (int64_t)imaxpct - mp->m_sb.sb_imax_pct;
+	xfs_trans_mod_sb(tp, XFS_TRANS_SB_IMAXPCT, dpct);
+	xfs_trans_set_sync(tp);
+	return xfs_trans_commit(tp);
+}
+
 /*
  * protected versions of growfs function acquire and release locks on the mount
  * point - exported through ioctls: XFS_IOC_FSGROWFSDATA, XFS_IOC_FSGROWFSLOG,
  * XFS_IOC_FSGROWFSRT
  */
-
-
 int
 xfs_growfs_data(
-	xfs_mount_t		*mp,
-	xfs_growfs_data_t	*in)
+	struct xfs_mount	*mp,
+	struct xfs_growfs_data	*in)
 {
-	int error;
+	int			error = 0;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 	if (!mutex_trylock(&mp->m_growlock))
 		return -EWOULDBLOCK;
+
+	/* update imaxpct separately to the physical grow of the filesystem */
+	if (in->imaxpct != mp->m_sb.sb_imax_pct) {
+		error = xfs_growfs_imaxpct(mp, in->imaxpct);
+		if (error)
+			goto out_error;
+	}
+
+	if (in->newblocks != mp->m_sb.sb_dblocks) {
 		error = xfs_growfs_data_private(mp, in);
+		if (error)
+			goto out_error;
+	}
+
+	/* Post growfs calculations needed to reflect new state in operations */
+	if (mp->m_sb.sb_imax_pct) {
+		uint64_t icount = mp->m_sb.sb_dblocks * mp->m_sb.sb_imax_pct;
+		do_div(icount, 100);
+		mp->m_maxicount = icount << mp->m_sb.sb_inopblog;
+	} else
+		mp->m_maxicount = 0;
+
+out_error:
 	/*
 	 * Increment the generation unconditionally, the error could be from
 	 * updating the secondary superblocks, in which case the new size