xfs: replace xfs_mod_incore_sb_batched

Introduce helper functions for modifying fields in the superblock
into xfs_trans.c, the only caller of xfs_mod_incore_sb_batch().  We
can then use these directly in xfs_trans_unreserve_and_mod_sb() and
so remove another user of the xfs_mode_incore_sb() API without
losing any functionality or scalability of the transaction commit
code..

Based on a patch 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/xfs_mount.c

@@ -1352,57 +1352,6 @@ xfs_mod_incore_sb(
 	return status;
 }
 
-/*
- * Change more than one field in the in-core superblock structure at a time.
- *
- * The fields and changes to those fields are specified in the array of
- * xfs_mod_sb structures passed in.  Either all of the specified deltas
- * will be applied or none of them will.  If any modified field dips below 0,
- * then all modifications will be backed out and EINVAL will be returned.
- *
- * Note that this function may not be used for the superblock values that
- * are tracked with the in-memory per-cpu counters - a direct call to
- * xfs_mod_incore_sb is required for these.
- */
-int
-xfs_mod_incore_sb_batch(
-	struct xfs_mount	*mp,
-	xfs_mod_sb_t		*msb,
-	uint			nmsb,
-	int			rsvd)
-{
-	xfs_mod_sb_t		*msbp;
-	int			error = 0;
-
-	/*
-	 * Loop through the array of mod structures and apply each individually.
-	 * If any fail, then back out all those which have already been applied.
-	 * Do all of this within the scope of the m_sb_lock so that all of the
-	 * changes will be atomic.
-	 */
-	spin_lock(&mp->m_sb_lock);
-	for (msbp = msb; msbp < (msb + nmsb); msbp++) {
-		ASSERT(msbp->msb_field < XFS_SBS_ICOUNT ||
-		       msbp->msb_field > XFS_SBS_FDBLOCKS);
-
-		error = xfs_mod_incore_sb_unlocked(mp, msbp->msb_field,
-						   msbp->msb_delta, rsvd);
-		if (error)
-			goto unwind;
-	}
-	spin_unlock(&mp->m_sb_lock);
-	return 0;
-
-unwind:
-	while (--msbp >= msb) {
-		error = xfs_mod_incore_sb_unlocked(mp, msbp->msb_field,
-						   -msbp->msb_delta, rsvd);
-		ASSERT(error == 0);
-	}
-	spin_unlock(&mp->m_sb_lock);
-	return error;
-}
-
 /*
  * xfs_getsb() is called to obtain the buffer for the superblock.
  * The buffer is returned locked and read in from disk.

fs/xfs/xfs_mount.h

@@ -259,15 +259,6 @@ xfs_daddr_to_agbno(struct xfs_mount *mp, xfs_daddr_t d)
 	return (xfs_agblock_t) do_div(ld, mp->m_sb.sb_agblocks);
 }
 
-/*
- * This structure is for use by the xfs_mod_incore_sb_batch() routine.
- * xfs_growfs can specify a few fields which are more than int limit
- */
-typedef struct xfs_mod_sb {
-	xfs_sb_field_t	msb_field;	/* Field to modify, see below */
-	int64_t		msb_delta;	/* Change to make to specified field */
-} xfs_mod_sb_t;
-
 /*
  * Per-ag incore structure, copies of information in agf and agi, to improve the
  * performance of allocation group selection.
@@ -325,8 +316,6 @@ extern int	xfs_initialize_perag(xfs_mount_t *mp, xfs_agnumber_t agcount,
 
 extern void	xfs_unmountfs(xfs_mount_t *);
 extern int	xfs_mod_incore_sb(xfs_mount_t *, xfs_sb_field_t, int64_t, int);
-extern int	xfs_mod_incore_sb_batch(xfs_mount_t *, xfs_mod_sb_t *,
-			uint, int);
 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,

fs/xfs/xfs_trans.c

@@ -485,6 +485,54 @@ xfs_trans_apply_sb_deltas(
 				  sizeof(sbp->sb_frextents) - 1);
 }
 
+STATIC int
+xfs_sb_mod8(
+	uint8_t			*field,
+	int8_t			delta)
+{
+	int8_t			counter = *field;
+
+	counter += delta;
+	if (counter < 0) {
+		ASSERT(0);
+		return -EINVAL;
+	}
+	*field = counter;
+	return 0;
+}
+
+STATIC int
+xfs_sb_mod32(
+	uint32_t		*field,
+	int32_t			delta)
+{
+	int32_t			counter = *field;
+
+	counter += delta;
+	if (counter < 0) {
+		ASSERT(0);
+		return -EINVAL;
+	}
+	*field = counter;
+	return 0;
+}
+
+STATIC int
+xfs_sb_mod64(
+	uint64_t		*field,
+	int64_t			delta)
+{
+	int64_t			counter = *field;
+
+	counter += delta;
+	if (counter < 0) {
+		ASSERT(0);
+		return -EINVAL;
+	}
+	*field = counter;
+	return 0;
+}
+
 /*
  * xfs_trans_unreserve_and_mod_sb() is called to release unused reservations
  * and apply superblock counter changes to the in-core superblock.  The
@@ -492,13 +540,6 @@ xfs_trans_apply_sb_deltas(
  * applied to the in-core superblock.  The idea is that that has already been
  * done.
  *
- * This is done efficiently with a single call to xfs_mod_incore_sb_batch().
- * However, we have to ensure that we only modify each superblock field only
- * once because the application of the delta values may not be atomic. That can
- * lead to ENOSPC races occurring if we have two separate modifcations of the
- * free space counter to put back the entire reservation and then take away
- * what we used.
- *
  * If we are not logging superblock counters, then the inode allocated/free and
  * used block counts are not updated in the on disk superblock. In this case,
  * XFS_TRANS_SB_DIRTY will not be set when the transaction is updated but we
@@ -506,20 +547,15 @@ xfs_trans_apply_sb_deltas(
  */
 void
 xfs_trans_unreserve_and_mod_sb(
-	xfs_trans_t	*tp)
+	struct xfs_trans	*tp)
 {
-	xfs_mod_sb_t	msb[9];	/* If you add cases, add entries */
-	xfs_mod_sb_t	*msbp;
-	xfs_mount_t	*mp = tp->t_mountp;
-	/* REFERENCED */
-	int		error;
-	bool		rsvd = (tp->t_flags & XFS_TRANS_RESERVE) != 0;
-	int64_t		blkdelta = 0;
-	int64_t		rtxdelta = 0;
-	int64_t		idelta = 0;
-	int64_t		ifreedelta = 0;
-
-	msbp = msb;
+	struct xfs_mount	*mp = tp->t_mountp;
+	bool			rsvd = (tp->t_flags & XFS_TRANS_RESERVE) != 0;
+	int64_t			blkdelta = 0;
+	int64_t			rtxdelta = 0;
+	int64_t			idelta = 0;
+	int64_t			ifreedelta = 0;
+	int			error;
 
 	/* calculate deltas */
 	if (tp->t_blk_res > 0)
@@ -560,72 +596,90 @@ xfs_trans_unreserve_and_mod_sb(
 			goto out_undo_icount;
 	}
 
+	if (rtxdelta == 0 && !(tp->t_flags & XFS_TRANS_SB_DIRTY))
+		return;
+
 	/* apply remaining deltas */
+	spin_lock(&mp->m_sb_lock);
 	if (rtxdelta) {
-		error = xfs_mod_frextents(mp, rtxdelta);
+		error = xfs_sb_mod64(&mp->m_sb.sb_frextents, rtxdelta);
 		if (error)
 			goto out_undo_ifree;
 	}
 
-	if (tp->t_flags & XFS_TRANS_SB_DIRTY) {
-		if (tp->t_dblocks_delta != 0) {
-			msbp->msb_field = XFS_SBS_DBLOCKS;
-			msbp->msb_delta = tp->t_dblocks_delta;
-			msbp++;
-		}
-		if (tp->t_agcount_delta != 0) {
-			msbp->msb_field = XFS_SBS_AGCOUNT;
-			msbp->msb_delta = tp->t_agcount_delta;
-			msbp++;
-		}
-		if (tp->t_imaxpct_delta != 0) {
-			msbp->msb_field = XFS_SBS_IMAX_PCT;
-			msbp->msb_delta = tp->t_imaxpct_delta;
-			msbp++;
-		}
-		if (tp->t_rextsize_delta != 0) {
-			msbp->msb_field = XFS_SBS_REXTSIZE;
-			msbp->msb_delta = tp->t_rextsize_delta;
-			msbp++;
-		}
-		if (tp->t_rbmblocks_delta != 0) {
-			msbp->msb_field = XFS_SBS_RBMBLOCKS;
-			msbp->msb_delta = tp->t_rbmblocks_delta;
-			msbp++;
-		}
-		if (tp->t_rblocks_delta != 0) {
-			msbp->msb_field = XFS_SBS_RBLOCKS;
-			msbp->msb_delta = tp->t_rblocks_delta;
-			msbp++;
-		}
-		if (tp->t_rextents_delta != 0) {
-			msbp->msb_field = XFS_SBS_REXTENTS;
-			msbp->msb_delta = tp->t_rextents_delta;
-			msbp++;
-		}
-		if (tp->t_rextslog_delta != 0) {
-			msbp->msb_field = XFS_SBS_REXTSLOG;
-			msbp->msb_delta = tp->t_rextslog_delta;
-			msbp++;
-		}
-	}
-
-	/*
-	 * If we need to change anything, do it.
-	 */
-	if (msbp > msb) {
-		error = xfs_mod_incore_sb_batch(tp->t_mountp, msb,
-			(uint)(msbp - msb), rsvd);
+	if (tp->t_dblocks_delta != 0) {
+		error = xfs_sb_mod64(&mp->m_sb.sb_dblocks, tp->t_dblocks_delta);
 		if (error)
 			goto out_undo_frextents;
 	}
-
+	if (tp->t_agcount_delta != 0) {
+		error = xfs_sb_mod32(&mp->m_sb.sb_agcount, tp->t_agcount_delta);
+		if (error)
+			goto out_undo_dblocks;
+	}
+	if (tp->t_imaxpct_delta != 0) {
+		error = xfs_sb_mod8(&mp->m_sb.sb_imax_pct, tp->t_imaxpct_delta);
+		if (error)
+			goto out_undo_agcount;
+	}
+	if (tp->t_rextsize_delta != 0) {
+		error = xfs_sb_mod32(&mp->m_sb.sb_rextsize,
+				     tp->t_rextsize_delta);
+		if (error)
+			goto out_undo_imaxpct;
+	}
+	if (tp->t_rbmblocks_delta != 0) {
+		error = xfs_sb_mod32(&mp->m_sb.sb_rbmblocks,
+				     tp->t_rbmblocks_delta);
+		if (error)
+			goto out_undo_rextsize;
+	}
+	if (tp->t_rblocks_delta != 0) {
+		error = xfs_sb_mod64(&mp->m_sb.sb_rblocks, tp->t_rblocks_delta);
+		if (error)
+			goto out_undo_rbmblocks;
+	}
+	if (tp->t_rextents_delta != 0) {
+		error = xfs_sb_mod64(&mp->m_sb.sb_rextents,
+				     tp->t_rextents_delta);
+		if (error)
+			goto out_undo_rblocks;
+	}
+	if (tp->t_rextslog_delta != 0) {
+		error = xfs_sb_mod8(&mp->m_sb.sb_rextslog,
+				     tp->t_rextslog_delta);
+		if (error)
+			goto out_undo_rextents;
+	}
+	spin_unlock(&mp->m_sb_lock);
 	return;
 
+out_undo_rextents:
+	if (tp->t_rextents_delta)
+		xfs_sb_mod64(&mp->m_sb.sb_rextents, -tp->t_rextents_delta);
+out_undo_rblocks:
+	if (tp->t_rblocks_delta)
+		xfs_sb_mod64(&mp->m_sb.sb_rblocks, -tp->t_rblocks_delta);
+out_undo_rbmblocks:
+	if (tp->t_rbmblocks_delta)
+		xfs_sb_mod32(&mp->m_sb.sb_rbmblocks, -tp->t_rbmblocks_delta);
+out_undo_rextsize:
+	if (tp->t_rextsize_delta)
+		xfs_sb_mod32(&mp->m_sb.sb_rextsize, -tp->t_rextsize_delta);
+out_undo_imaxpct:
+	if (tp->t_rextsize_delta)
+		xfs_sb_mod8(&mp->m_sb.sb_imax_pct, -tp->t_imaxpct_delta);
+out_undo_agcount:
+	if (tp->t_agcount_delta)
+		xfs_sb_mod32(&mp->m_sb.sb_agcount, -tp->t_agcount_delta);
+out_undo_dblocks:
+	if (tp->t_dblocks_delta)
+		xfs_sb_mod64(&mp->m_sb.sb_dblocks, -tp->t_dblocks_delta);
 out_undo_frextents:
 	if (rtxdelta)
-		xfs_mod_frextents(mp, -rtxdelta);
+		xfs_sb_mod64(&mp->m_sb.sb_frextents, -rtxdelta);
 out_undo_ifree:
+	spin_unlock(&mp->m_sb_lock);
 	if (ifreedelta)
 		xfs_mod_ifree(mp, -ifreedelta);
 out_undo_icount: