Introduce per-AG writeback worker infrastructure at mount time.
This patch adds initialization and teardown only, without changing
writeback behavior.

Signed-off-by: Kundan Kumar <kundan.kumar@samsung.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
---
 fs/xfs/xfs_aops.c  | 79 ++++++++++++++++++++++++++++++++++++++++++++++
 fs/xfs/xfs_aops.h  |  3 ++
 fs/xfs/xfs_mount.c |  2 ++
 fs/xfs/xfs_mount.h | 10 ++++++
 fs/xfs/xfs_super.c |  2 ++
 5 files changed, 96 insertions(+)

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index a26f79815533..9d5b65922cd2 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -23,6 +23,23 @@
 #include "xfs_zone_alloc.h"
 #include "xfs_rtgroup.h"
 
+#define XFS_AG_TASK_POOL_MIN 1024
+
+struct xfs_ag_wb_task {
+	struct list_head list;
+	struct xfs_inode *ip;
+	struct writeback_control wbc;
+	xfs_agnumber_t agno;
+};
+
+struct xfs_ag_wb {
+	struct delayed_work ag_work;
+	spinlock_t lock;
+	struct list_head task_list;
+	xfs_agnumber_t agno;
+	struct xfs_mount *mp;
+};
+
 struct xfs_writepage_ctx {
 	struct iomap_writepage_ctx ctx;
 	unsigned int		data_seq;
@@ -666,6 +683,68 @@ static const struct iomap_writeback_ops xfs_zoned_writeback_ops = {
 	.writeback_submit	= xfs_zoned_writeback_submit,
 };
 
+void
+xfs_init_ag_writeback(struct xfs_mount *mp)
+{
+	xfs_agnumber_t agno;
+
+	mp->m_ag_wq = alloc_workqueue("xfs-ag-wb", WQ_UNBOUND | WQ_MEM_RECLAIM,
+				      0);
+	if (!mp->m_ag_wq)
+		return;
+
+	mp->m_ag_wb = kcalloc(mp->m_sb.sb_agcount,
+				sizeof(struct xfs_ag_wb),
+				GFP_KERNEL);
+
+	if (!mp->m_ag_wb) {
+		destroy_workqueue(mp->m_ag_wq);
+		mp->m_ag_wq = NULL;
+		return;
+	}
+
+	for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
+		struct xfs_ag_wb *awb = &mp->m_ag_wb[agno];
+
+		spin_lock_init(&awb->lock);
+		INIT_LIST_HEAD(&awb->task_list);
+		awb->agno = agno;
+		awb->mp = mp;
+	}
+
+	mp->m_ag_task_cachep = kmem_cache_create("xfs_ag_wb_task",
+						sizeof(struct xfs_ag_wb_task),
+						0,
+						SLAB_RECLAIM_ACCOUNT,
+						NULL);
+
+	mp->m_ag_task_pool = mempool_create_slab_pool(XFS_AG_TASK_POOL_MIN,
+	mp->m_ag_task_cachep);
+
+	if (!mp->m_ag_task_pool) {
+		kmem_cache_destroy(mp->m_ag_task_cachep);
+		mp->m_ag_task_cachep = NULL;
+	}
+}
+
+void
+xfs_destroy_ag_writeback(struct xfs_mount *mp)
+{
+	if (mp->m_ag_wq) {
+		flush_workqueue(mp->m_ag_wq);
+		destroy_workqueue(mp->m_ag_wq);
+		mp->m_ag_wq = NULL;
+	}
+	kfree(mp->m_ag_wb);
+	mp->m_ag_wb = NULL;
+
+	mempool_destroy(mp->m_ag_task_pool);
+	mp->m_ag_task_pool = NULL;
+
+	kmem_cache_destroy(mp->m_ag_task_cachep);
+	mp->m_ag_task_cachep = NULL;
+}
+
 STATIC int
 xfs_vm_writepages(
 	struct address_space	*mapping,
diff --git a/fs/xfs/xfs_aops.h b/fs/xfs/xfs_aops.h
index 5a7a0f1a0b49..e84acb7e8ca8 100644
--- a/fs/xfs/xfs_aops.h
+++ b/fs/xfs/xfs_aops.h
@@ -12,4 +12,7 @@ extern const struct address_space_operations xfs_dax_aops;
 int xfs_setfilesize(struct xfs_inode *ip, xfs_off_t offset, size_t size);
 void xfs_end_bio(struct bio *bio);
 
+void xfs_init_ag_writeback(struct xfs_mount *mp);
+void xfs_destroy_ag_writeback(struct xfs_mount *mp);
+
 #endif /* __XFS_AOPS_H__ */
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 0953f6ae94ab..26224503c4bf 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -1323,6 +1323,8 @@ xfs_unmountfs(
 
 	xfs_qm_unmount(mp);
 
+	xfs_destroy_ag_writeback(mp);
+
 	/*
 	 * Unreserve any blocks we have so that when we unmount we don't account
 	 * the reserved free space as used. This is really only necessary for
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index b871dfde372b..c44155de2883 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -342,6 +342,16 @@ typedef struct xfs_mount {
 
 	/* Hook to feed dirent updates to an active online repair. */
 	struct xfs_hooks	m_dir_update_hooks;
+
+
+	/* global XFS AG writeback wq */
+	struct workqueue_struct *m_ag_wq;
+	/* array of [sb_agcount] */
+	struct xfs_ag_wb        *m_ag_wb;
+
+	/* task cache and pool */
+	struct kmem_cache *m_ag_task_cachep;
+	mempool_t *m_ag_task_pool;
 } xfs_mount_t;
 
 #define M_IGEO(mp)		(&(mp)->m_ino_geo)
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index bc71aa9dcee8..73f8d2942df4 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1765,6 +1765,8 @@ xfs_fs_fill_super(
 	if (error)
 		goto out_free_sb;
 
+	xfs_init_ag_writeback(mp);
+
 	/*
 	 * V4 support is undergoing deprecation.
 	 *
-- 
2.25.1