xfs: convert trim to use for_each_perag_range

To convert it to using active perag references and hence make it
shrink safe.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

fs/xfs/xfs_discard.c

@@ -21,23 +21,20 @@
 
 STATIC int
 xfs_trim_extents(
-	struct xfs_mount	*mp,
-	xfs_agnumber_t		agno,
+	struct xfs_perag	*pag,
 	xfs_daddr_t		start,
 	xfs_daddr_t		end,
 	xfs_daddr_t		minlen,
 	uint64_t		*blocks_trimmed)
 {
+	struct xfs_mount	*mp = pag->pag_mount;
 	struct block_device	*bdev = mp->m_ddev_targp->bt_bdev;
 	struct xfs_btree_cur	*cur;
 	struct xfs_buf		*agbp;
 	struct xfs_agf		*agf;
-	struct xfs_perag	*pag;
 	int			error;
 	int			i;
 
-	pag = xfs_perag_get(mp, agno);
-
 	/*
 	 * Force out the log.  This means any transactions that might have freed
 	 * space before we take the AGF buffer lock are now on disk, and the
@@ -47,7 +44,7 @@ xfs_trim_extents(
 
 	error = xfs_alloc_read_agf(pag, NULL, 0, &agbp);
 	if (error)
-		goto out_put_perag;
+		return error;
 	agf = agbp->b_addr;
 
 	cur = xfs_allocbt_init_cursor(mp, NULL, agbp, pag, XFS_BTNUM_CNT);
@@ -71,10 +68,10 @@ xfs_trim_extents(
 
 		error = xfs_alloc_get_rec(cur, &fbno, &flen, &i);
 		if (error)
-			goto out_del_cursor;
+			break;
 		if (XFS_IS_CORRUPT(mp, i != 1)) {
 			error = -EFSCORRUPTED;
-			goto out_del_cursor;
+			break;
 		}
 		ASSERT(flen <= be32_to_cpu(agf->agf_longest));
 
@@ -83,15 +80,15 @@ xfs_trim_extents(
 		 * the format the range/len variables are supplied in by
 		 * userspace.
 		 */
-		dbno = XFS_AGB_TO_DADDR(mp, agno, fbno);
+		dbno = XFS_AGB_TO_DADDR(mp, pag->pag_agno, fbno);
 		dlen = XFS_FSB_TO_BB(mp, flen);
 
 		/*
 		 * Too small?  Give up.
 		 */
 		if (dlen < minlen) {
-			trace_xfs_discard_toosmall(mp, agno, fbno, flen);
-			goto out_del_cursor;
+			trace_xfs_discard_toosmall(mp, pag->pag_agno, fbno, flen);
+			break;
 		}
 
 		/*
@@ -100,7 +97,7 @@ xfs_trim_extents(
 		 * down partially overlapping ranges for now.
 		 */
 		if (dbno + dlen < start || dbno > end) {
-			trace_xfs_discard_exclude(mp, agno, fbno, flen);
+			trace_xfs_discard_exclude(mp, pag->pag_agno, fbno, flen);
 			goto next_extent;
 		}
 
@@ -109,32 +106,30 @@ xfs_trim_extents(
 		 * discard and try again the next time.
 		 */
 		if (xfs_extent_busy_search(mp, pag, fbno, flen)) {
-			trace_xfs_discard_busy(mp, agno, fbno, flen);
+			trace_xfs_discard_busy(mp, pag->pag_agno, fbno, flen);
 			goto next_extent;
 		}
 
-		trace_xfs_discard_extent(mp, agno, fbno, flen);
+		trace_xfs_discard_extent(mp, pag->pag_agno, fbno, flen);
 		error = blkdev_issue_discard(bdev, dbno, dlen, GFP_NOFS);
 		if (error)
-			goto out_del_cursor;
+			break;
 		*blocks_trimmed += flen;
 
 next_extent:
 		error = xfs_btree_decrement(cur, 0, &i);
 		if (error)
-			goto out_del_cursor;
+			break;
 
 		if (fatal_signal_pending(current)) {
 			error = -ERESTARTSYS;
-			goto out_del_cursor;
+			break;
 		}
 	}
 
 out_del_cursor:
 	xfs_btree_del_cursor(cur, error);
 	xfs_buf_relse(agbp);
-out_put_perag:
-	xfs_perag_put(pag);
 	return error;
 }
 
@@ -152,11 +147,12 @@ xfs_ioc_trim(
 	struct xfs_mount		*mp,
 	struct fstrim_range __user	*urange)
 {
+	struct xfs_perag	*pag;
 	unsigned int		granularity =
 		bdev_discard_granularity(mp->m_ddev_targp->bt_bdev);
 	struct fstrim_range	range;
 	xfs_daddr_t		start, end, minlen;
-	xfs_agnumber_t		start_agno, end_agno, agno;
+	xfs_agnumber_t		agno;
 	uint64_t		blocks_trimmed = 0;
 	int			error, last_error = 0;
 
@@ -193,18 +189,18 @@ xfs_ioc_trim(
 	end = start + BTOBBT(range.len) - 1;
 
 	if (end > XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks) - 1)
-		end = XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks)- 1;
-
-	start_agno = xfs_daddr_to_agno(mp, start);
-	end_agno = xfs_daddr_to_agno(mp, end);
+		end = XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks) - 1;
 
-	for (agno = start_agno; agno <= end_agno; agno++) {
-		error = xfs_trim_extents(mp, agno, start, end, minlen,
+	agno = xfs_daddr_to_agno(mp, start);
+	for_each_perag_range(mp, agno, xfs_daddr_to_agno(mp, end), pag) {
+		error = xfs_trim_extents(pag, start, end, minlen,
 					  &blocks_trimmed);
 		if (error) {
 			last_error = error;
-			if (error == -ERESTARTSYS)
+			if (error == -ERESTARTSYS) {
+				xfs_perag_rele(pag);
 				break;
+			}
 		}
 	}