xfs: introduce xfs_mod_frextents

Add a new helper to modify the incore counter of free realtime
extents. This matches the helpers used for inode and data block
counters, and removes a significant users of the xfs_mod_incore_sb()
interface.

Based on a patch originally from Christoph Hellwig.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/libxfs/xfs_bmap.c

@@ -4158,8 +4158,7 @@ xfs_bmapi_reserve_delalloc(
 	ASSERT(indlen > 0);
 
 	if (rt) {
-		error = xfs_mod_incore_sb(mp, XFS_SBS_FREXTENTS,
-					  -((int64_t)extsz), 0);
+		error = xfs_mod_frextents(mp, -((int64_t)extsz));
 	} else {
 		error = xfs_mod_fdblocks(mp, -((int64_t)alen), false);
 	}
@@ -4194,7 +4193,7 @@ xfs_bmapi_reserve_delalloc(
 
 out_unreserve_blocks:
 	if (rt)
-		xfs_mod_incore_sb(mp, XFS_SBS_FREXTENTS, extsz, 0);
+		xfs_mod_frextents(mp, extsz);
 	else
 		xfs_mod_fdblocks(mp, alen, false);
 out_unreserve_quota:
@@ -5278,8 +5277,7 @@ xfs_bunmapi(
 
 				rtexts = XFS_FSB_TO_B(mp, del.br_blockcount);
 				do_div(rtexts, mp->m_sb.sb_rextsize);
-				xfs_mod_incore_sb(mp, XFS_SBS_FREXTENTS,
-						(int64_t)rtexts, 0);
+				xfs_mod_frextents(mp, (int64_t)rtexts);
 				(void)xfs_trans_reserve_quota_nblks(NULL,
 					ip, -((long)del.br_blockcount), 0,
 					XFS_QMOPT_RES_RTBLKS);

fs/xfs/xfs_mount.c

@@ -1198,6 +1198,24 @@ xfs_mod_fdblocks(
 	return -ENOSPC;
 }
 
+int
+xfs_mod_frextents(
+	struct xfs_mount	*mp,
+	int64_t			delta)
+{
+	int64_t			lcounter;
+	int			ret = 0;
+
+	spin_lock(&mp->m_sb_lock);
+	lcounter = mp->m_sb.sb_frextents + delta;
+	if (lcounter < 0)
+		ret = -ENOSPC;
+	else
+		mp->m_sb.sb_frextents = lcounter;
+	spin_unlock(&mp->m_sb_lock);
+	return ret;
+}
+
 /*
  * xfs_mod_incore_sb_unlocked() is a utility routine commonly used to apply
  * a delta to a specified field in the in-core superblock.  Simply
@@ -1227,16 +1245,9 @@ xfs_mod_incore_sb_unlocked(
 	case XFS_SBS_ICOUNT:
 	case XFS_SBS_IFREE:
 	case XFS_SBS_FDBLOCKS:
+	case XFS_SBS_FREXTENTS:
 		ASSERT(0);
 		return -EINVAL;
-	case XFS_SBS_FREXTENTS:
-		lcounter = (long long)mp->m_sb.sb_frextents;
-		lcounter += delta;
-		if (lcounter < 0) {
-			return -ENOSPC;
-		}
-		mp->m_sb.sb_frextents = lcounter;
-		return 0;
 	case XFS_SBS_DBLOCKS:
 		lcounter = (long long)mp->m_sb.sb_dblocks;
 		lcounter += delta;

fs/xfs/xfs_mount.h

@@ -331,6 +331,8 @@ extern int	xfs_mod_icount(struct xfs_mount *mp, int64_t delta);
 extern int	xfs_mod_ifree(struct xfs_mount *mp, int64_t delta);
 extern int	xfs_mod_fdblocks(struct xfs_mount *mp, int64_t delta,
 				 bool reserved);
+extern int	xfs_mod_frextents(struct xfs_mount *mp, int64_t delta);
+
 extern int	xfs_mount_log_sb(xfs_mount_t *);
 extern struct xfs_buf *xfs_getsb(xfs_mount_t *, int);
 extern int	xfs_readsb(xfs_mount_t *, int);

fs/xfs/xfs_trans.c

@@ -235,8 +235,7 @@ xfs_trans_reserve(
 	 * fail if the count would go below zero.
 	 */
 	if (rtextents > 0) {
-		error = xfs_mod_incore_sb(tp->t_mountp, XFS_SBS_FREXTENTS,
-					  -((int64_t)rtextents), rsvd);
+		error = xfs_mod_frextents(tp->t_mountp, -((int64_t)rtextents));
 		if (error) {
 			error = -ENOSPC;
 			goto undo_log;
@@ -562,10 +561,10 @@ xfs_trans_unreserve_and_mod_sb(
 	}
 
 	/* apply remaining deltas */
-	if (rtxdelta != 0) {
-		msbp->msb_field = XFS_SBS_FREXTENTS;
-		msbp->msb_delta = rtxdelta;
-		msbp++;
+	if (rtxdelta) {
+		error = xfs_mod_frextents(mp, rtxdelta);
+		if (error)
+			goto out_undo_ifree;
 	}
 
 	if (tp->t_flags & XFS_TRANS_SB_DIRTY) {
@@ -618,12 +617,15 @@ xfs_trans_unreserve_and_mod_sb(
 		error = xfs_mod_incore_sb_batch(tp->t_mountp, msb,
 			(uint)(msbp - msb), rsvd);
 		if (error)
-			goto out_undo_ifreecount;
+			goto out_undo_frextents;
 	}
 
 	return;
 
-out_undo_ifreecount:
+out_undo_frextents:
+	if (rtxdelta)
+		xfs_mod_frextents(mp, -rtxdelta);
+out_undo_ifree:
 	if (ifreedelta)
 		xfs_mod_ifree(mp, -ifreedelta);
 out_undo_icount: