xfs: give xfs_bmap_intent its own perag reference

Give the xfs_bmap_intent an active reference to the perag structure
data.  This reference will be used to enable scrub intent draining
functionality in subsequent patches.  Later, shrink will use these
passive references to know if an AG is quiesced or not.

The reason why we take a passive ref for a file mapping operation is
simple: we're committing to some sort of action involving space in an
AG, so we want to indicate our interest in that AG.  The space is
already allocated, so we need to be able to operate on AGs that are
offline or being shrunk.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

3 files changed, 33 insertions, 1 deletions

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 34de6e6898c4..0b4fb3979bdc 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -6075,6 +6075,7 @@ __xfs_bmap_add(
 	bi->bi_whichfork = whichfork;
 	bi->bi_bmap = *bmap;
 
+	xfs_bmap_update_get_group(tp->t_mountp, bi);
 	xfs_defer_add(tp, XFS_DEFER_OPS_TYPE_BMAP, &bi->bi_list);
 	return 0;
 }
diff --git a/fs/xfs/libxfs/xfs_bmap.h b/fs/xfs/libxfs/xfs_bmap.h
index dd08361ca5a6..e5a492027aea 100644
--- a/fs/xfs/libxfs/xfs_bmap.h
+++ b/fs/xfs/libxfs/xfs_bmap.h
@@ -238,9 +238,13 @@ struct xfs_bmap_intent {
 	enum xfs_bmap_intent_type		bi_type;
 	int					bi_whichfork;
 	struct xfs_inode			*bi_owner;
+	struct xfs_perag			*bi_pag;
 	struct xfs_bmbt_irec			bi_bmap;
 };
 
+void xfs_bmap_update_get_group(struct xfs_mount *mp,
+		struct xfs_bmap_intent *bi);
+
 int	xfs_bmap_finish_one(struct xfs_trans *tp, struct xfs_bmap_intent *bi);
 void	xfs_bmap_map_extent(struct xfs_trans *tp, struct xfs_inode *ip,
 		struct xfs_bmbt_irec *imap);
diff --git a/fs/xfs/xfs_bmap_item.c b/fs/xfs/xfs_bmap_item.c
index 6e2f0013380a..8f0f33d07d2c 100644
--- a/fs/xfs/xfs_bmap_item.c
+++ b/fs/xfs/xfs_bmap_item.c
@@ -24,6 +24,7 @@
 #include "xfs_error.h"
 #include "xfs_log_priv.h"
 #include "xfs_log_recover.h"
+#include "xfs_ag.h"
 
 struct kmem_cache	*xfs_bui_cache;
 struct kmem_cache	*xfs_bud_cache;
@@ -363,6 +364,26 @@ xfs_bmap_update_create_done(
 	return &xfs_trans_get_bud(tp, BUI_ITEM(intent))->bud_item;
 }
 
+/* Take a passive ref to the AG containing the space we're mapping. */
+void
+xfs_bmap_update_get_group(
+	struct xfs_mount	*mp,
+	struct xfs_bmap_intent	*bi)
+{
+	xfs_agnumber_t		agno;
+
+	agno = XFS_FSB_TO_AGNO(mp, bi->bi_bmap.br_startblock);
+	bi->bi_pag = xfs_perag_get(mp, agno);
+}
+
+/* Release a passive AG ref after finishing mapping work. */
+static inline void
+xfs_bmap_update_put_group(
+	struct xfs_bmap_intent	*bi)
+{
+	xfs_perag_put(bi->bi_pag);
+}
+
 /* Process a deferred rmap update. */
 STATIC int
 xfs_bmap_update_finish_item(
@@ -381,6 +402,8 @@ xfs_bmap_update_finish_item(
 		ASSERT(bi->bi_type == XFS_BMAP_UNMAP);
 		return -EAGAIN;
 	}
+
+	xfs_bmap_update_put_group(bi);
 	kmem_cache_free(xfs_bmap_intent_cache, bi);
 	return error;
 }
@@ -393,7 +416,7 @@ xfs_bmap_update_abort_intent(
 	xfs_bui_release(BUI_ITEM(intent));
 }
 
-/* Cancel a deferred rmap update. */
+/* Cancel a deferred bmap update. */
 STATIC void
 xfs_bmap_update_cancel_item(
 	struct list_head		*item)
@@ -401,6 +424,8 @@ xfs_bmap_update_cancel_item(
 	struct xfs_bmap_intent		*bi;
 
 	bi = container_of(item, struct xfs_bmap_intent, bi_list);
+
+	xfs_bmap_update_put_group(bi);
 	kmem_cache_free(xfs_bmap_intent_cache, bi);
 }
 
@@ -509,10 +534,12 @@ xfs_bui_item_recover(
 	fake.bi_bmap.br_state = (map->me_flags & XFS_BMAP_EXTENT_UNWRITTEN) ?
 			XFS_EXT_UNWRITTEN : XFS_EXT_NORM;
 
+	xfs_bmap_update_get_group(mp, &fake);
 	error = xfs_trans_log_finish_bmap_update(tp, budp, &fake);
 	if (error == -EFSCORRUPTED)
 		XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, map,
 				sizeof(*map));
+	xfs_bmap_update_put_group(&fake);
 	if (error)
 		goto err_cancel;