xfs: give xfs_extfree_intent its own perag reference

Give the xfs_extfree_intent an passive reference to the perag structure
data.  This reference will be used to enable scrub intent draining
functionality in subsequent patches.  The space being freed must already
be allocated, so we need to able to run even if the AG is being offlined
or shrunk.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/libxfs/xfs_alloc.c

@@ -2405,6 +2405,7 @@ xfs_defer_agfl_block(
 
 	trace_xfs_agfl_free_defer(mp, agno, 0, agbno, 1);
 
+	xfs_extent_free_get_group(mp, xefi);
 	xfs_defer_add(tp, XFS_DEFER_OPS_TYPE_AGFL_FREE, &xefi->xefi_list);
 }
 
@@ -2421,8 +2422,8 @@ __xfs_free_extent_later(
 	bool				skip_discard)
 {
 	struct xfs_extent_free_item	*xefi;
-#ifdef DEBUG
 	struct xfs_mount		*mp = tp->t_mountp;
+#ifdef DEBUG
 	xfs_agnumber_t			agno;
 	xfs_agblock_t			agbno;
 
@@ -2456,9 +2457,11 @@ __xfs_free_extent_later(
 	} else {
 		xefi->xefi_owner = XFS_RMAP_OWN_NULL;
 	}
-	trace_xfs_bmap_free_defer(tp->t_mountp,
+	trace_xfs_bmap_free_defer(mp,
 			XFS_FSB_TO_AGNO(tp->t_mountp, bno), 0,
 			XFS_FSB_TO_AGBNO(tp->t_mountp, bno), len);
+
+	xfs_extent_free_get_group(mp, xefi);
 	xfs_defer_add(tp, XFS_DEFER_OPS_TYPE_FREE, &xefi->xefi_list);
 }
 

fs/xfs/libxfs/xfs_alloc.h

@@ -237,9 +237,13 @@ struct xfs_extent_free_item {
 	uint64_t		xefi_owner;
 	xfs_fsblock_t		xefi_startblock;/* starting fs block number */
 	xfs_extlen_t		xefi_blockcount;/* number of blocks in extent */
+	struct xfs_perag	*xefi_pag;
 	unsigned int		xefi_flags;
 };
 
+void xfs_extent_free_get_group(struct xfs_mount *mp,
+		struct xfs_extent_free_item *xefi);
+
 #define XFS_EFI_SKIP_DISCARD	(1U << 0) /* don't issue discard */
 #define XFS_EFI_ATTR_FORK	(1U << 1) /* freeing attr fork block */
 #define XFS_EFI_BMBT_BLOCK	(1U << 2) /* freeing bmap btree block */

fs/xfs/xfs_extfree_item.c

@@ -350,10 +350,7 @@ xfs_trans_free_extent(
 	struct xfs_owner_info		oinfo = { };
 	struct xfs_mount		*mp = tp->t_mountp;
 	struct xfs_extent		*extp;
-	struct xfs_perag		*pag;
 	uint				next_extent;
-	xfs_agnumber_t			agno = XFS_FSB_TO_AGNO(mp,
-							xefi->xefi_startblock);
 	xfs_agblock_t			agbno = XFS_FSB_TO_AGBNO(mp,
 							xefi->xefi_startblock);
 	int				error;
@@ -364,14 +361,12 @@ xfs_trans_free_extent(
 	if (xefi->xefi_flags & XFS_EFI_BMBT_BLOCK)
 		oinfo.oi_flags |= XFS_OWNER_INFO_BMBT_BLOCK;
 
-	trace_xfs_bmap_free_deferred(tp->t_mountp, agno, 0, agbno,
-			xefi->xefi_blockcount);
+	trace_xfs_bmap_free_deferred(tp->t_mountp, xefi->xefi_pag->pag_agno, 0,
+			agbno, xefi->xefi_blockcount);
 
-	pag = xfs_perag_get(mp, agno);
-	error = __xfs_free_extent(tp, pag, agbno, xefi->xefi_blockcount,
-			&oinfo, XFS_AG_RESV_NONE,
+	error = __xfs_free_extent(tp, xefi->xefi_pag, agbno,
+			xefi->xefi_blockcount, &oinfo, XFS_AG_RESV_NONE,
 			xefi->xefi_flags & XFS_EFI_SKIP_DISCARD);
-	xfs_perag_put(pag);
 
 	/*
 	 * Mark the transaction dirty, even on error. This ensures the
@@ -400,14 +395,13 @@ xfs_extent_free_diff_items(
 	const struct list_head		*a,
 	const struct list_head		*b)
 {
-	struct xfs_mount		*mp = priv;
 	struct xfs_extent_free_item	*ra;
 	struct xfs_extent_free_item	*rb;
 
 	ra = container_of(a, struct xfs_extent_free_item, xefi_list);
 	rb = container_of(b, struct xfs_extent_free_item, xefi_list);
-	return  XFS_FSB_TO_AGNO(mp, ra->xefi_startblock) -
-		XFS_FSB_TO_AGNO(mp, rb->xefi_startblock);
+
+	return ra->xefi_pag->pag_agno - rb->xefi_pag->pag_agno;
 }
 
 /* Log a free extent to the intent item. */
@@ -466,6 +460,26 @@ xfs_extent_free_create_done(
 	return &xfs_trans_get_efd(tp, EFI_ITEM(intent), count)->efd_item;
 }
 
+/* Take a passive ref to the AG containing the space we're freeing. */
+void
+xfs_extent_free_get_group(
+	struct xfs_mount		*mp,
+	struct xfs_extent_free_item	*xefi)
+{
+	xfs_agnumber_t			agno;
+
+	agno = XFS_FSB_TO_AGNO(mp, xefi->xefi_startblock);
+	xefi->xefi_pag = xfs_perag_get(mp, agno);
+}
+
+/* Release a passive AG ref after some freeing work. */
+static inline void
+xfs_extent_free_put_group(
+	struct xfs_extent_free_item	*xefi)
+{
+	xfs_perag_put(xefi->xefi_pag);
+}
+
 /* Process a free extent. */
 STATIC int
 xfs_extent_free_finish_item(
@@ -480,6 +494,8 @@ xfs_extent_free_finish_item(
 	xefi = container_of(item, struct xfs_extent_free_item, xefi_list);
 
 	error = xfs_trans_free_extent(tp, EFD_ITEM(done), xefi);
+
+	xfs_extent_free_put_group(xefi);
 	kmem_cache_free(xfs_extfree_item_cache, xefi);
 	return error;
 }
@@ -500,6 +516,8 @@ xfs_extent_free_cancel_item(
 	struct xfs_extent_free_item	*xefi;
 
 	xefi = container_of(item, struct xfs_extent_free_item, xefi_list);
+
+	xfs_extent_free_put_group(xefi);
 	kmem_cache_free(xfs_extfree_item_cache, xefi);
 }
 
@@ -530,24 +548,21 @@ xfs_agfl_free_finish_item(
 	struct xfs_extent		*extp;
 	struct xfs_buf			*agbp;
 	int				error;
-	xfs_agnumber_t			agno;
 	xfs_agblock_t			agbno;
 	uint				next_extent;
-	struct xfs_perag		*pag;
 
 	xefi = container_of(item, struct xfs_extent_free_item, xefi_list);
 	ASSERT(xefi->xefi_blockcount == 1);
-	agno = XFS_FSB_TO_AGNO(mp, xefi->xefi_startblock);
 	agbno = XFS_FSB_TO_AGBNO(mp, xefi->xefi_startblock);
 	oinfo.oi_owner = xefi->xefi_owner;
 
-	trace_xfs_agfl_free_deferred(mp, agno, 0, agbno, xefi->xefi_blockcount);
+	trace_xfs_agfl_free_deferred(mp, xefi->xefi_pag->pag_agno, 0, agbno,
+			xefi->xefi_blockcount);
 
-	pag = xfs_perag_get(mp, agno);
-	error = xfs_alloc_read_agf(pag, tp, 0, &agbp);
+	error = xfs_alloc_read_agf(xefi->xefi_pag, tp, 0, &agbp);
 	if (!error)
-		error = xfs_free_agfl_block(tp, agno, agbno, agbp, &oinfo);
-	xfs_perag_put(pag);
+		error = xfs_free_agfl_block(tp, xefi->xefi_pag->pag_agno,
+				agbno, agbp, &oinfo);
 
 	/*
 	 * Mark the transaction dirty, even on error. This ensures the
@@ -566,6 +581,7 @@ xfs_agfl_free_finish_item(
 	extp->ext_len = xefi->xefi_blockcount;
 	efdp->efd_next_extent++;
 
+	xfs_extent_free_put_group(xefi);
 	kmem_cache_free(xfs_extfree_item_cache, xefi);
 	return error;
 }
@@ -636,7 +652,9 @@ xfs_efi_item_recover(
 		fake.xefi_startblock = extp->ext_start;
 		fake.xefi_blockcount = extp->ext_len;
 
+		xfs_extent_free_get_group(mp, &fake);
 		error = xfs_trans_free_extent(tp, efdp, &fake);
+		xfs_extent_free_put_group(&fake);
 		if (error == -EFSCORRUPTED)
 			XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp,
 					extp, sizeof(*extp));